Why you should stick to the 85w90 oil spec Guzzi chose

[Philnewbike]

Hello
Due to a severe case of OCD and or displacement behaviour I have been reading a shed load of oil information (not on forums, in journals). This is what I’ve learnt based on my search for a gearbox (GB) and final drive (FD) oil for my Breva 1100 CARC... just for scientific fun  . The manual states 85w90 GL5 oil for GB and 80w90 GL4 oil for FD. These are listed as Agip/ENI oil products named MP/S 85w90 and MP 80w90. This seems to be standard for all CARC bikes. So why would Guzzi stipulate two apparently only slightly different grades and standards (85w GL5 and 80w GL4)? Hard to know, but ENI 85w90 MP/S datasheet says its suitable for trucks, very apt! When I looked (in the UK) for 85w90 the choice is very slim and when I asked the nice people at Opie oils they said Redline light shock proof oil 75w90 and swore this was superior (because forums say it is…). I don’t wish to insult our American cousins but when I read the claims of Redline I immediately think ‘snake oil salesman’. Maybe the stuff is good in dragsters but for everyday Sunday motorbike rides? Nah. Plus there are plenty of tails saying it turns to milkshake when in contact with moisture, which occasionally used bikes or ones that are left standing with have due to condensation. So, what about another more down to earth 75w90 Opie also recommended? Afterall, the 90 weight is there and the 75w will just make it easier to shift when cooler yes? Well, I don’t think so. If you look at the datasheets for the oils you will see that the standard way of comparing viscosities is centistokes (cSt) of viscosity at 40 C and 100 C (roughly 100 F and 200 F). Guzzi spec 90 weight ENI MP/S oil has a viscosity of 18.5 cSt at 100C and a viscosity of 206 cSt at 40C. Now, the thing is, do MG gearboxes operate at 100C? I guess not (not measured it sadly… if anyone has a laser heat sensor thing an can zap their GB that would be great). The engine oil temp is ~100C and the GB will very likely operate lower than that. I am going to guesstimate 70C. At 70C the MP/S 85w90 oil has a viscosity of about 60 cSt (from log viscosity vs linear temp plot - as is standard in oil viscosity work). At 70C the Redline not-snake-oil has a viscosity of 40 cSt. Now this is a lot lower. At 100C they are similar, but I don’t think the box runs that hot unless it was raced. Now for the Guzzi spec 80w90 FD oil. This will most probably run cooler than the GB, I’m guestimating 50C (again, can anyone check this?). The datasheet for MG ENI MP 80w90 oil has a viscosity of 15 and 144 cSt at 100 and 40 degrees C respectively. At 50C this equates to 100 cSt and for the Redline it is 75 cSt – again, much lower. In other words, I think Guzzi designed the spec so that at the inbetween temperatures that the GB and FD operate at the viscosity of the chosen oil is high enough to give protection at that point and the FD probably needs a little more viscosity (at a lower temperature) because of the FD bevel extreme pressure. I also imagine the GL4 is due to some tiny element of yellow metal somewhere, or they weren't sure so erred for caution. Thus, I have chosen Fuchs 85w90 GL5 bus oil (hey, it hits the spec!  ) for the GB and Fuchs/Silkoline GL4 80w90 for the FD as they have very close viscosity ratings to the unavailable Agip/ENI spec’d oils.

Now you can all call me a muppet and swear your grandma ran a Road King for 300,000 miles on pink milkshake  (But seriously, I am interested in the engineering scientific side of things, but not "I ran it for 5000 miles and it didn't blow up argument)

[skippy]

Spot on. I really appreciate your collection of supporting data on the always contentious "oil thread" subject. I also use the specified oils as specified by the manufactures. They are the ones with the real need to insure the reliability and thus longevity of their products after all. They have spent and enormous amount of engineering effort creating those specifications.
As a side note in your remarks about the "pink milkshake" phenomena, ALL oils are subject to water absorption but the design of the CARC final drive is such that the likely hood of pully moisture in from the atmosphere is more likely. The little bellows seal boot around the reaction arm acts as a bellows type pump when the final CARC unit is travelling up and down in it's range of motion. And when it is wet out while doing this the moisture just simply gets drawn in. The best defense for this is to fit up a remote breather, mine is routed all the way up to my airbox.
Additionally, a little known fact on moisture in oil. One tenth of one percent (.1%) water in oil will diminish the lubricity of the oil by 50%! Now most applications that use oil such as engines and gearbox's operate at high enough temperatures' (100 C) to keep the moisture out but for those of us who regularly ride for short distances this can become a very costly mistake.

Just my 2 cents, thanks for sharing

Skippy       

[kballowe]

One of my owners manuals specified AGIP Rotra MP and so I set out to find a reasonable replacement.  Valvoline and Castrol products were very close to the specified AGIP product - and Mobil Delvac 1 came in as a virtual match.  All of these have the MT-1 rating (manual transmission rating) which includes a seal conditioner.

The owners manual for one of my newer Guzzis specifies "Castrol Products"

I even have a liter of Genuine Moto Guzzi final drive oil, with moly.  The instructions on the container state to "shake well before using".

Many of us simply purchase 75W-90 [insert brand name here] and pour it into everywhere that wants gear oil.

[guzziart]

Hi Phil & Skippy,

Interesting read!  I thought the GL4 vs GL5 in older Guzzi's had something to do with plastic bearing cages or bronze bushings somewhere in the transmission...idk.

For me, whatever the vehicle manufacturers recommended SAE or JASO spec recommends is what I use.  I am one of those thrifty characters that will use any inexpensive brand that meets OEM recommended spec oil.  Unfortunately, I most always end up changing oil before the recommended mileage or time interval unless I'm on a trip with the bike.  Some of my bikes only get a few K miles per year so the change interval is once per year....what a waste, please don't report me to the Oil Change police.

Additionally, the color of the new oil (red, purple, etc.) means nothing to me.  I would take no pride in bragging about the Regal Purple, Shat Proof Red or IsSoil that I spent a few hours of wages on but could not prove it works better than any of the other offerings out there.  The same goes for the color of used/drain oil unless there are obvious signs of moisture (milky appearance, etc.) or fuel dilution.  Dirty oil is dirty oil to me.  If I ever get real concerned, I'll send it out for oil analysis.  Ok, so now you know my thoughts on oil. 

[egschade]

I also use the Guzzi specified oils and change them all (engine, transmission and gearbox) at 3K miles or 6 months, whichever comes first. Oil is cheap compared to engine repairs.

Had MOS (milky oil syndrome) with my Griso due to shorter winter commutes. Solution was twofold: 1) block off the oil cooler to retain heat and 2) take the long way to get the engine hot enough to boil off the condensate. Other bikes didn't seem to suffer as badly in the same conditions.

[guzziart]

Hey Kballowe,

I ran into the same thing in the owners manual for my V11 Lemans... AGIP Rotra but I got lucky with the shop manual that specified an an SAE oil too.

[Bisbee]

Ay caramba! A gearbox oil thread! I took my first bike , a K75C , to the dealer for its breakin service. 5000 miles later I changed the fluids myself. The “mechanic “ forgot to put oil back into the gearbox.  Found out later he was a coke head. Never had a problem. Maybe it’s all just a big oil conspiracy .👁👁👁 The truth is out there. Actually, in the south Florida heat, the standard has been Mobil 1 75-90. But opinions vary. I suspect that viscosity ranges are more critical in colder climes where temps don’t rise so quickly.

[Ncdan]

It’s raining and I’m bored so I’ll just throw out an opinion based on nothing except what I’ve done over the past 45 years with my personal motorcycles.
Except in extreme circumstances such as drastic temperatures changes, environmental conditions and racing use, I don’t believe one can notice much if any different in minor changes in motor oil or differential oil lubricants, as far as weights or synthetics. I have never experienced any adverse conditions when I have done these changes in the past.
Continue please:)

[skippy]

Hi Phil & Skippy,

Interesting read!  I thought the GL4 vs GL5 in older Guzzi's had something to do with plastic bearing cages or bronze bushings somewhere in the transmission...idk.

For me, whatever the vehicle manufacturers recommended SAE or JASO spec recommends is what I use.  I am one of those thrifty characters that will use any inexpensive brand that meets OEM recommended spec oil.  Unfortunately, I most always end up changing oil before the recommended mileage or time interval unless I'm on a trip with the bike.  Some of my bikes only get a few K miles per year so the change interval is once per year....what a waste, please don't report me to the Oil Change police.

Additionally, the color of the new oil (red, purple, etc.) means nothing to me.  I would take no pride in bragging about the Regal Purple, Shat Proof Red or IsSoil that I spent a few hours of wages on but could not prove it works better than any of the other offerings out there.  The same goes for the color of used/drain oil unless there are obvious signs of moisture (milky appearance, etc.) or fuel dilution.  Dirty oil is dirty oil to me.  If I ever get real concerned, I'll send it out for oil analysis.  Ok, so now you know my thoughts on oil. 

I forgot to mention that oil with .1% moisture will show very little signs of contamination visually.

I also use the Guzzi specified oils and change them all (engine, transmission and gearbox) at 3K miles or 6 months, whichever comes first. Oil is cheap compared to engine repairs.

Had MOS (milky oil syndrome) with my Griso due to shorter winter commutes. Solution was twofold: 1) block off the oil cooler to retain heat and 2) take the long way to get the engine hot enough to boil off the condensate. Other bikes didn't seem to suffer as badly in the same conditions.

Frustratingly enough Moto Guzzi discontinued the use of a thermostatically controlled oil cooler on the CARC bikes after the 2-valve bike such as mine and Philnewbike's 1100 Breva's. Why? Who the hell knows, just silly in my opinion.

Skippy

 

[John Warner]

As a side note in your remarks about the "pink milkshake" phenomena, ALL oils are subject to water absorption but the design of the CARC final drive is such that the likely hood of pully moisture in from the atmosphere is more likely. The little bellows seal boot around the reaction arm acts as a bellows type pump when the final CARC unit is travelling up and down in it's range of motion. And when it is wet out while doing this the moisture just simply gets drawn in. The best defense for this is to fit up a remote breather, mine is routed all the way up to my airbox.
Additionally, a little known fact on moisture in oil. One tenth of one percent (.1%) water in oil will diminish the lubricity of the oil by 50%! Now most applications that use oil such as engines and gearbox's operate at high enough temperatures' (100 C) to keep the moisture out but for those of us who regularly ride for short distances this can become a very costly mistake.

Skippy       

A remote Breather for the CARC Unit is a must I'd say, did my Stelvio one not long after I got it in Sep 2015.
The Oil is always clean when I change it, barely any change from when it went in.

As for Engine Oil temps, the Stelvio, and I'm guessing the Griso and any other 1100/1200 Engine with an Oil Cooler and no Thermostat is badly over-cooled.

I fitted a Trail Tech Oil Temp Sensor and Gauge soon after I got the Bike, partly due to the Flat Tappet concerns.

In Winter, or just cool weather (<14°C or so), my Oil would never get above 75°C or so, less if it rained as well.
Would always have 'Mayo' in the Valve Covers.
I took to partially/fully covering the Cooler in Winter, to get the Temps up to a decent level (110-120°C), no more Mayo.
Then I built a Thermostat Unit, using a 93°C Waxstat, and put it in the Cooling Oil Circuit, to bypass the Cooler.
Temp Sensor was originally in the Banjo Bolt in the Cooling Oil Outlet from the Crankcase (see pic).
I've since moved it to the Sump, next to the Drain Plug.




I also machined up a replacement Alloy Fill Plug for the CARC Unit, that accepts another Trail Tech Sensor (with Gauge obviously).
Highest temp seen so far is around 42°C, during our decent (for once) Summer, in 2019.
I'm going to fit it to the Gearbox Fill/Level hole at the next service, just out of interest.



geojson python

[Philnewbike]

Thank you for your appreciative comments. You would not believe how much info i have acquired... think I'm going mad with oil data! Maybe I should have explained the plot though: the dashed lines with the labelled numbers are the guzzi spec. Also, I should have said that perhaps the reason the small block non-CARC bikes have 140 weight oil is that those final drives run a bit hotter and so need to be thicker oil to start with. Not sure why they would be hotter though? Basically the reason I don't think you can just run 75w90 is because the 90 bit isn't the weight of the oil at the temperature a guzzi operates at, i.e. it is not going to be 100 C more likely lower, so you don't want a 75w weight as it will be a bit too thin. Though as someone above said, if it's oily it's probably ok. My argument with that is that overwhelming the people who say " I've run bikes for 50 year on olive oil" etc have never run one for 10,000 miles on the same oil and compared the wear rates to an identical bike ran for 10,000 miles on the right spec.
Also. A word about those who run on heavier oil, e.g. 75w140 when 85w90 is specified: High viscosity oil in an application where a medium viscosity is appropriate will simply shear more at the gear tooth interface and that friction may cause momentary heat to a point where its viscosity is LOWER than the right lower spec 90 weight. Thats not my opinion its tribological fact. So you can produce more wear going for a 'safe' heavier oil. Not saying thats definitely the case here, but possible. At the very least you'll be using more fuel and possibly straining the seals. Word to the wise: stick to the spec and peace out oil thread addicts 

Oh, one more confounding issue: the v9 and v85tt look almost identical to me but the v85 gearbox is specified with 140 oil and v9 is 90! I think this may be due to the possibility that the v85 will be used off road 2 up and so the oil will be hotter,  load higher, and so the viscosity should be higher as its expectedto thin out... not sure tbh

[LesP]

I would need to see more pants suspenders and corn cob pipe smoking first.

This is what I removed.





The new FD gears and gearbox clusters got Redline Shockproof Heavy.
Time will tell if I look inside or something overheats beforehand.

[Philnewbike]

A remote Breather for the CARC Unit is a must I'd say, did my Stelvio one not long after I got it in Sep 2015.
The Oil is always clean when I change it, barely any change from when it went in.

As for Engine Oil temps, the Stelvio, and I'm guessing the Griso and any other 1100/1200 Engine with an Oil Cooler and no Thermostat is badly over-cooled.

I fitted a Trail Tech Oil Temp Sensor and Gauge soon after I got the Bike, partly due to the Flat Tappet concerns.

In Winter, or just cool weather (<14°C or so), my Oil would never get above 75°C or so, less if it rained as well.
Would always have 'Mayo' in the Valve Covers.
I took to partially/fully covering the Cooler in Winter, to get the Temps up to a decent level (110-120°C), no more Mayo.
Then I built a Thermostat Unit, using a 93°C Waxstat, and put it in the Cooling Oil Circuit, to bypass the Cooler.
Temp Sensor was originally in the Banjo Bolt in the Cooling Oil Outlet from the Crankcase (see pic).
I've since moved it to the Sump, next to the Drain Plug.




I also machined up a replacement Alloy Fill Plug for the CARC Unit, that accepts another Trail Tech Sensor (with Gauge obviously).
Highest temp seen so far is around 42°C, during our decent (for once) Summer, in 2019.
I'm going to fit it to the Gearbox Fill/Level hole at the next service, just out of interest.



geojson python

That is amazing work mate and really interesting. So if you read off from my plot from about 42 deg C then the Guzzi spec oil viscosity is basically at the 40 deg / 140 cSt level and the 75w90 Redline not-snake-oil is at 100 cSt... lots lower. Will be fascinated to see what the gearbox temp is 

How hard wss it to rig up this interesting system?

[Philnewbike]

ALL oils are subject to water absorption but the design of the CARC final drive is such that the likely hood of pully moisture in from the atmosphere is more likely. The little bellows seal boot around the reaction arm acts as a bellows type pump when the final CARC unit is travelling up and down in it's range of motion. And when it is wet out while doing this the moisture just simply gets drawn in. The best defense for this is to fit up a remote breather,

Just my 2 cents, thanks for sharing

Skippy       

Thanks skippy, good point !

[Philnewbike]

I would need to see more pants suspenders and corn cob pipe smoking first.

This is what I removed.

Lol.

What on earth happened? Were you running in olive oil?

[LesP]

 Fuchs/Silkoline GL4 80w90.

[lucky phil]

That is amazing work mate and really interesting. So if you read off from my plot from about 42 deg C then the Guzzi spec oil viscosity is basically at the 40 deg / 140 cSt level and the 75w90 Redline not-snake-oil is at 100 cSt... lots lower.

How hard wss it to rig up this interesting system?

And in practical application this means precisely what? Higher viscosity is always required? Guzzi oil recommendations for viscosity are always precisely what's needed in all circumstances? You might be surprised at what rationale is used in the manufacturers world with regards to specifications on a lot of things. It's regularly not always a direct technical consideration. I see this thread with regards to the specific hair splitting over precise viscosity as a bit of naval gazing by people that think manufacturers treat this question as anally as some of their customers. They don't and cant when they are selling machinery all over the world to be used in a multitude of applications and ways.
I'm aware of the relationship between theory and practice and I have many many times drilled down to the theoretical fine point when I need to but when I have years of first hand practical knowledge I don't waste time on the theory. The facts are that millions and millions of motorcycle straight cut transmissions in applications driven by engines with far more power and torque than a Guzzi twin happily survive hundreds of thousands of KLM's without issue on 10/15W-40/50 engine oil. They also happily survive when you subject them to racing conditions without complaint. A Guzzi gearbox has the luxury of operating with dedicated transmission oil and you're concerning yourself with the viscosity differences between oils rated in the same grade. I mean knock yourself out but it's in the area of OCD as you mentioned and of no practical benefit.

Ciao 

[Scout63]

I go the other way and get brand loyal across my bikes.  Redline Shockproof in gearboxes and Honda GN4 in cranks. I just wish oil filters were all the same size.

[Brand X]

Be sure to send your oil in to Blackstone labs every 3 miles, and then will will know for sure if things are going correctly. otherwise total guess.. Maybe send your fork oil in too..

[coast range rider]

Thank you for starting this thread @Philnewbike. Because I've always wondered why MG bothered to specify different FD and gearbox oils. And what the difference is using the more mass produced full synthetic 75w90. There are differences besides viscosity, but I don't have those answers here.

I believe the designs are for high reliability operating in sub freezing ambient temperatures as well as sweltering summer ambients in the hottest deserts. It appears to me the viscosity differences between the different oils in the graph is a magnitude less than the difference for the given spec'ed oil at the temperature extremes I mentioned.

This leads me to summarize that the greatest variance is when using 75w-90 in coldest winter when the oil is too thin, but hey, if oil this thin then is a problem, then all the oils would be even thinner in hottest summer. I hope my logic comes through here, it is a simple idea, but a little hard for me to describe.

[Old Jock]

And in practical application this means precisely what? Higher viscosity is always required? Guzzi oil recommendations for viscosity are always precisely what's needed in all circumstances? You might be surprised at what rationale is used in the manufacturers world with regards to specifications on a lot of things. It's regularly not always a direct technical consideration. I see this thread with regards to the specific hair splitting over precise viscosity as a bit of naval gazing by people that think manufacturers treat this question as anally as some of their customers. They don't and cant when they are selling machinery all over the world to be used in a multitude of applications and ways.
I'm aware of the relationship between theory and practice and I have many many times drilled down to the theoretical fine point when I need to but when I have years of first hand practical knowledge I don't waste time on the theory. The facts are that millions and millions of motorcycle straight cut transmissions in applications driven by engines with far more power and torque than a Guzzi twin happily survive hundreds of thousands of KLM's without issue on 10/15W-40/50 engine oil. They also happily survive when you subject them to racing conditions without complaint. A Guzzi gearbox has the luxury of operating with dedicated transmission oil and you're concerning yourself with the viscosity differences between oils rated in the same grade. I mean knock yourself out but it's in the area of OCD as you mentioned and of no practical benefit.

 

Ciao

[Philnewbike]

Fuchs/Silkoline GL4 80w90.

@LesP

What bike is that failed final drive from? It doesn't look like a CARC... Looking at old Guzzi manuals the V50 sized FDs stipulate Agip F.1 Rotra MP SAE 140 and the 850 tyoes are straight 90. Note that 90 weight is heavier than a xW90 weight oil so if you used 80w90 instead of 90 it will also be too thin at the operating temperature (i.e. that is well below 100C / 200F). I have added the Silkolene/Fuchs straight 90 weight to the chart in red (and changed the x axis for clarity), as you can see it is very viscos because it has no W rating.

Impossible to say for sure, but from the engineering textbooks on gear wear this looks like scuffing and, or followed by, severe overheating - thermal runaway (caused by gears expanding and running without backlash which increases the loads causing increased temperature...etc). However, contrary to that they also seem to show the very tips of the teeth worn which actually would suggest far too much clearance, i.e. slipping (was this after the wear occurred perhaps?). What may have caused all this? Well 80w90 is too thin for an older non-CARC bike according to the Guzzi spec. Perhaps maintenance or lack of done by previous owners accelerated damage before you got it: bearing misalignment due to wear or misassembly either at factory or previous repair, snake oil additive added by misguided owners, too thick viscosity oil (though you say this wasn't the case) or too thin, low oil, too high oil causing frothing, too much axial float or water contamination. Or, plain old too many miles on the clock!

[Philnewbike]

I have years of first hand practical knowledge I don't waste time on the theory. The facts are that millions and millions of motorcycle straight cut transmissions in applications driven by engines with far more power and torque than a Guzzi twin happily survive hundreds of thousands of KLM's without issue on 10/15W-40/50 engine oil.

Hi Phil
I'm a mechanical engineer in R&D so this is a little side step for me because the science of gearbox design and failure is not that familiar to me... but it is becoming so due to OCD lol. Just a couple of things I'd say I disagree with but am happy for you to carry on believing so this isn't meant to be combative:
If you're not interested in theory then yes, choose whatever has the biggest advertising budget and looks cool (Redline I suspect).
As far as I know straight cut gears don't tent to fail early here, it's the dog clutches that do... and the bevel final drive... and seals.
10w40 and 15w50 engine oil is probably OK for gearbox but definitely not OK for final drive which needs extreme pressure EP additive.
10w40 and 15w50 engine oil has equivalent gear oil weights of roughly 75w90 or there abouts so is probably a little thin for gearbox but will most likely be fine as you say. If you put it in the FD you will wear it out faster. it'll be too thin and not have EP protection. That's not to say it won't last 100Km for some people but is will be wearing far higher rate as it's not got the right EP additives.
Why not just stick to the spec? Sorry, I keep forgetting, gearbox designers spend all that time and brain power designing how many microns of gear clearance are needed for the bending load on the teeth and then when it comes to choosing the oil they go "ah, just stick something cool-looking in with a cool name".
No mate, they honestly don't.
Toodle-pip!
Phil

[Philnewbike]

Thank you for starting this thread @Philnewbike. Because I've always wondered why MG bothered to specify different FD and gearbox oils. And what the difference is using the more mass produced full synthetic 75w90. There are differences besides viscosity, but I don't have those answers here.

I believe the designs are for high reliability operating in sub freezing ambient temperatures as well as sweltering summer ambients in the hottest deserts. It appears to me the viscosity differences between the different oils in the graph is a magnitude less than the difference for the given spec'ed oil at the temperature extremes I mentioned.

This leads me to summarize that the greatest variance is when using 75w-90 in coldest winter when the oil is too thin, but hey, if oil this thin then is a problem, then all the oils would be even thinner in hottest summer. I hope my logic comes through here, it is a simple idea, but a little hard for me to describe.

Thanks mate, it is all academic, just for OCD kicks. I'd probably say that the operating temperature once warm will not vary significantly and therefore ambient temperature, unless sub 5 C or post 40 C is probably all covered in the spec. Or, if riding 2-up in hills or off road this might be an issue too. So outside those parameters then yes I'd probably consider fiddling with the spec but then again I wouldn't bother riding in sub 5 C I'd get the bus!

[Philnewbike]

Fuchs/Silkoline GL4 80w90.

I've just realised I'm UK not USA, when I say gearbox I should be clear I mean the thing with the gears in - that needs 85w90 in a CARC and straight 90 for the 1970s 850 or straight 140 for 1970s V50 (as examples)
When I say final drive or transmission I mean the swing arm shaft bit - 80w90 in a CARC and same straight 90 850 or 140 V50 style as above for older Guzzis I've seen the manuals for.

Cheers
phil

[Philnewbike]

I also machined up a replacement Alloy Fill Plug for the CARC Unit, that accepts another Trail Tech Sensor (with Gauge obviously).
Highest temp seen so far is around 42°C, during our decent (for once) Summer, in 2019.
I'm going to fit it to the Gearbox Fill/Level hole at the next service, just out of interest.



geojson python

Great work! Will be fascinated to see the gearbox temp. So at 42 deg C the 80w90 Guzzi spec oil is at ~140 cSt and the Reline not-at-all-snake-oil is at ~100 cSt. That’s a third less viscosity. Maybe that isn't enough to cause damage but I see no reason to risk it especially as a proper EP specific gear oil hits the Guzzi spec at a fraction of the price.

[Two Checks]

Hmm....if using X140 lube will cause viscosity loss due to heat why would Guzzi specify X140 lube in an off road application due to heat?
The reason Guzzi or any otber manufacturer says to use a certain brand of oil is because they are paid to do so.
And the "milkshake" thing about Red Line gear oil comes from the Shock Proof Heavy looking like a strawberry milkshake as it comes from the bottle. Most any oil will look like a milkshake or mayo when water is involved.


The GL-4 rating on gear lubes USED to be due to non ferrous metals in the transmission-the thing we shift by foot on bikes and by hand in cages. GL-5 USED to attack those metals. There are now GL-5 oils which are compatible with non ferrous metals.

[Old Jock]

Most on here who run Redline use the Heavy not the Light

I don't know about the CARC bikes, too dammed modern for me.

With the older 5 speeders the majority of the gears are Helical not straight cut.

The few that are unfortunate enough to run straight cut 5 speeders, usually end up digging into the box a LOT earlier, me included because the gear surface treatment was inadequate.

The straight cut boxes sometimes make more noise than the engines.

If you've dug into one of these old boxes and seen the way Louigi put these things together, IMHO the finer points of gear oil is probably the least of your worries.

This is before we get to Guzzi reducing the dogs from 5 to 3 in a hopeless attempt to speed up the shifting, all it did was make the boxes even noisier and resulted in these boxes needing attenion earlier than their older brothers. Or we could discuss the twin row all metal bearings that Guzzi changed to phenolic/nylon caged with around half the balls type without a change of part number.

I could go on as many, many on here could do likewise and more

I'm in some doubt regarding the depth of design that went on inside Mandello, because over the years they've made some howlers.

[Philnewbike]

Hmm....if using X140 lube will cause viscosity loss due to heat why would Guzzi specify X140 lube in an off road application due to heat?
The reason Guzzi or any otber manufacturer says to use a certain brand of oil is because they are paid to do so.
And the "milkshake" thing about Red Line gear oil comes from the Shock Proof Heavy looking like a strawberry milkshake as it comes from the bottle. Most any oil will look like a milkshake or mayo when water is involved.


The GL-4 rating on gear lubes USED to be due to non ferrous metals in the transmission-the thing we shift by foot on bikes and by hand in cages. GL-5 USED to attack those metals. There are now GL-5 oils which are compatible with non ferrous metals.

Heat: There are 2 kinds to consider, the heat at the meta-metal interface and the bulk heat of the sump. Going more slowly with higher load would indicate a higher viscosity required. Using a higher viscosity at high sliding speed can simply cause heating at the sliding interface due to the viscous heating.
Yes brand is for monetary agreement. But spec like 85w90 is for a reason.
The Redline is particularly sensitive to water contamination due to the (I think) calcium additive level.
Yes, some GL5 oils specifically say they're also GL4 compliant and that is important to check.

[Philnewbike]

Most on here who run Redline use the Heavy not the Light

With the older 5 speeders the majority of the gears are Helical not straight cut.

Heavy 140 oil *is recommended* for a lot of the small block final drives. Excessive gearbox wear could be due to wrong spec heavy weight dragster oil... maybe!
I was not aware of any box having helical gears. Interesting.