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

[Two Checks]

The statement was made and repeated using the heavier oil is bad due to added heat at the mating sufaces of of the gears.
If this is bad you wouldnt want to use the heavier spec oil under any condition.

[Philnewbike]

The statement was made and repeated using the heavier oil is bad due to added heat at the mating sufaces of of the gears.
If this is bad you wouldnt want to use the heavier spec oil under any condition.

Attached is the viscosity comparison chart with Redline heavy added. Note it is thinner than the Guzzi spec for 85w90 and thinner than the older Guzzi spec of straight 90 weight at the operating temperature (i.e. below 70 deg C).

No, saying "heavier oil is bad due to added heat at the mating sufaces of of the gears and so you wouldn't want to use the heavier spec oil under any condition", is patently not correct. In general and oversimplifying it: lower speed highly loaded tends to indicate heavier oil and vice versa.
Heavy weight oil is not bad under any conditions, it is simply unwise to use heavy weight oil when the gearbox manufacturer and their oil supplier say to use a medium one e.g. 85w90 and you use (e.g.) 75w140. I don't see how that is controversial. (Except what you're actually doing is probably using a thinner oil which I'll explain in a minute...!).
You're confusing two principles. One is that (e.g. Redline) 75w140 weight oil in a gearbox that's running at 50 deg C is heavier than 85w90 or straight 90. It isn't, it's actually lighter, so thinner than Guzzi/Agip expected. Look at the new plot with Redline 75w140 added: below 70 deg C the Redline is THINNER than the Guzzi spec. OK this may not be an issue, but we don't know so why risk it? (The gearbox runs cooler than the engine, especially so if you're a potterer like me.)
The second is general gearbox teeth design principle: oil is chosen to provide certain microns of oil film between teeth and some dog clutch engagement principles. If you then stick in a genuinely heavier oil of some kind then the film thickness increases and so does the friction heating of the shearing forces in the film. So instantaneously, at the tooth-to-tooth interface, you can get high temp LOWER viscosity oil film and hence less protection and higher temperatures. I'm not sure if this is a big issue here tbh but it's worth noting.
Interestingly the MP/S 85w90 spec sheet also shows there are limited slip friction modifiers in it suggesting that ideally an 85w90 or straight 90 for a LS diff would be best (maybe something to do with the sliding dog clutches in sequential boxes and avoiding too much slipperiness for positive engagement)... I'm not sure at this moment of my knowledge tbh 
Agip/ENI, though obviously they paid Guzzi for the privilege (just like Castrol now) of supplying, and the Guzzi engineers, know more about oil selection than Redline definitely-not-snake-oil-with-huge-marketing-budget do.

Obviously, if there's a lot of wear and the clearances have opened up to the point of noise generation then perhaps a heavier oil would then be appropriate, but not a 75w90 as the 75w bit makes it too thin at the expected operating temperature - which thanks to John Warner I estimate to be above 40 deg C and below 70 deg C. NB a chap above in the comments used an oil too thin for his final drive (80w90 - ignored the spec that says heavier weight) and look what happened (and now he says he's going to use redline shockproof, which is also thinner than the spec at the 40 deg C ... Why ignore the spec?


Cheers
phil

[Old Jock]

For the 5 speeders that I'm running the Guzzi recommendation is 80W-90 and the Redline Heavy's viscosity is higher

That's not to say I won't look at another brand later, but for this season I'll continue to use the Redline that's in the box for now.

It's also not to say that higher=good/lower=bad there are so many variables it's a pointless debate.

Generally we fall into 2 camps, you either stick rigidly to Guzzi's recommendations or you don't.

On the older bikes is the oil specified, the best for the gearboxbox/bevel box/engine currently available or the best that was available at the time of production?

Should I go to an 85W/90 instead?

As an aside engine oil recommended is 20/50 as that was about as good as it got back in the day, I'm currently running a 15/50 and thinking of going to a 10/50. Some of the carc's have a 10/60 recommended for their engines.........sho uld I be going there............Si gh

My own take is as long as the oils are generally within the ranges of common sense and your not running Yak Fat in the engine and mineral water in the transmission you'll probabaly be just fine.

Gettin' ma coat............... .....I should know better than to even post on oil threads

[Philnewbike]

For the 5 speeders that I'm running the Guzzi recommendation is 80W-90 and the Redline Heavy's viscosity is higher

That's not to say I won't look at another brand later, but for this season I'll continue to use the Redline that's in the box for now.

It's also not to say that higher=good/lower=bad there are so many variables it's a pointless debate.

Generally we fall into 2 camps, you either stick rigidly to Guzzi's recommendations or you don't.

On the older bikes is the oil specified, the best for the gearboxbox/bevel box/engine currently available or the best that was available at the time of production?

Should I go to an 85W/90 instead?

As an aside engine oil recommended is 20/50 as that was about as good as it got back in the day, I'm currently running a 15/50 and thinking of going to a 10/50. Some of the carc's have a 10/60 recommended for their engines.........sho uld I be going there............Si gh

My own take is as long as the oils are generally within the ranges of common sense and your not running Yak Fat in the engine and mineral water in the transmission you'll probabaly be just fine.

Gettin' ma coat............... .....I should know better than to even post on oil threads

For the 1000 5 speed the spec is indeed Agip MP 80w90 for gearbox and final drive. 75w90 Redline would be too thin and 75w140 Redline is a fair bit thicker. This might be a good thing if there's already wear in the box, but then again it may just cause excessive frictional shear heating and frothing degradation causing more wear. We'll never know so like you say, pointless to debate. There is known tribology science and there is anecdotal evidence. Both are interesting and anecdotal evidence is still valid... but sometimes there is some right nonsense spoken so you just have to be more careful.

As you say, this is all pointless at the end of the day, but I'm fascinated by the science and thought I'd share it just for kicks... you know you love a good oil thread, admit it 

[Two Checks]

Surprise, surprise! A 75 weight oil is thinner than an 85 weight! Whoda thunk it!
But, the statement was made that a higher viscosity oil creates more heat at contact points than thinner oil
In the exact transmission Guzzi recommends two different viscosities depending on use.
If the heavier oil creates more heat then why does Gizzi recommend a heavier oil in conditions that would create more heat is said heat at contact points is harmful?


Btw, I have no dog in the fight but I can tell ya I have used the shock proof heavy in quick change rears in 700+ HP dirt track cars. The gears show no wear whatsoever. And its hard to get the gars off their shafts because you can't grab them. Too slick.
That's why it's said not to be used in transmissions with synchros.

[Philnewbike]

Surprise, surprise! A 75 weight oil is thinner than an 85 weight! Whoda thunk it!

We were discussing 75w90 or 75w140 to 85w90 and yes it is indeed a surprise to many because they don't realise that their application is running at a temperature where a 75w90 or 75w140 is at the 'w' end of it's viscosity and not at the 90 or 140 end and therefore thinner than they think (and thinner than the Guzzi spec).

But, the statement was made that a higher viscosity oil creates more heat at contact points than thinner oil
In the exact transmission Guzzi recommends two different viscosities depending on use.
If the heavier oil creates more heat then why does Gizzi recommend a heavier oil in conditions that would create more heat is said heat at contact points is harmful?

Based on gearbox design theory I'd suggest because the transmission is assumed to be going more slowly at higher loads, which would suggest a higher viscosity and/or that the high loads will cause the gearbox to run hotter and therefore nearer to the 'hot end' of the xxWyy rating where the oil's thinner.

Btw, I have no dog in the fight but I can tell ya I have used the shock proof heavy in quick change rears in 700+ HP dirt track cars. The gears show no wear whatsoever. And its hard to get the gars off their shafts because you can't grab them. Too slick.
That's why it's said not to be used in transmissions with synchros.

Yes Redline's spec say's it is recommended for that kind of purpose.
Again, anecdotal is not compelling but is interesting. I don't think a 700 hp dirt bike used for minutes and then stripped down is very representative of lazy Guzzi riding though.

[lucky phil]

Surprise, surprise! A 75 weight oil is thinner than an 85 weight! Whoda thunk it!
But, the statement was made that a higher viscosity oil creates more heat at contact points than thinner oil
In the exact transmission Guzzi recommends two different viscosities depending on use.
If the heavier oil creates more heat then why does Gizzi recommend a heavier oil in conditions that would create more heat is said heat at contact points is harmful?


Btw, I have no dog in the fight but I can tell ya I have used the shock proof heavy in quick change rears in 700+ HP dirt track cars. The gears show no wear whatsoever. And its hard to get the gars off their shafts because you can't grab them. Too slick.
That's why it's said not to be used in transmissions with synchros.

I remember about 20 years ago when Pratt and Whitney were trying to develop a high bypass jet engine using a reduction gearbox for the fan they were running the gears in an oil bath and were having sever overheating issues. This gear system remember would be transmitting many thousands of shaft horsepower. The cure? less oil. They went to a targeted oil jet system directly at the gears and ditched the wet sump system. The churn was overheating the oil. Things aren't always simple to extrapolate without data and physical experience. You can hypothesise and pour over theory all you like and it's what you need to do sometimes but at the end of the day the actual doing of it is where the answers are. And there's plenty of gearbox and bevel gear practical lubricating data out there.
The other thing I recall was GMH here is Australia had a 4 speed manual gearbox they used in a lot of cars, the M21. Good box but had an issue with shifting when cold, esp in winter. The solution from GMH? Ditch the gear oil and run ATF. My father in law was involved in the testing and research on that one. Many thousands of those boxes ran many hundreds of thousands of KLM's for the rest of their lives on ATF without issues. So designed for gear oil and end up running for life on ATF.

Ciao   

[kingoffleece]

THX.  That's really interesting.

[Philnewbike]

I remember about 20 years ago when Pratt and Whitney were trying to develop a high bypass jet engine using a reduction gearbox for the fan they were running the gears in an oil bath and were having sever overheating issues. This gear system remember would be transmitting many thousands of shaft horsepower. The cure? less oil. They went to a targeted oil jet system directly at the gears and ditched the wet sump system. The churn was overheating the oil. Things aren't always simple to extrapolate without data and physical experience. You can hypothesise and pour over theory all you like and it's what you need to do sometimes but at the end of the day the actual doing of it is where the answers are. And there's plenty of gearbox and bevel gear practical lubricating data out there.
The other thing I recall was GMH here is Australia had a 4 speed manual gearbox they used in a lot of cars, the M21. Good box but had an issue with shifting when cold, esp in winter. The solution from GMH? Ditch the gear oil and run ATF. My father in law was involved in the testing and research on that one. Many thousands of those boxes ran many hundreds of thousands of KLM's for the rest of their lives on ATF without issues. So designed for gear oil and end up running for life on ATF.

Ciao

R&D is both theory and experimental (including field results) so these two examples sound interesting and eminently believable. In case you’re interested for rotational gear speeds >15 m/s my text book says you should use spray lubrication for superior cooling!
ATF in manual boxes is pretty common. Not sure why… I am not stuffing any more gear oil info into my head 
Toodle-pip

[moto-uno]

 Were those M21 trannies straight cut gears ?

[LesP]

Were those M21 trannies straight cut gears ?

That I recall they were all helical including the M22 'rock crusher (I bought a new M22 in the 1980's)
Plenty of folk have run ATF in Norton Commando gearbox's with no problems (but elected to use Redline in that application also)
#
I will stick to the snake oil milkshake (Heavy) in the Moto Guzzi gearbox and FD and soon to have Royal Purple 20/50 HPS.

[lucky phil]

Were those M21 trannies straight cut gears ?

No, road cars don't use straight cut transmissions as they would drive you nuts with the noise. ( someone will dig something up now I just know it) As an aside auto transmissions are full of gears, planetary gears for the most part and designed to be lubed by ATF but many big gears in an auto trans just the same.
On a Carc bike the biggest worry you have is the pinion nut hasn't loosened of as they are lightly torqued from the factory without thread locker (Roper info) and when the lock washer lets them back off it destroys the Carc, not the absolute precise grade of gear oil you use.
Here's another fact of life in cars and bikes. A significant amount of the time even the official dealer servicing DOESN'T use the grade of oil specified,if it's an unusual grade they dont normally carry or isn't used in their shop. I know this for a fact as I've seen the receipts for the oil used from a dealer service with the wrong grade of oil that was used on the servicing receipt many times. Plus of course from friends in the industry that service bikes. Manufacturers know this sort of thing happens and by and large engineer their products to tolerate this. They obviously make a requirement but are usually smart enough to have enough "head room" in the design to allow for deviations. I think there'd be quite a few Griso's running around happily on 15W-50 or 10W-50 instead of the 10W-60 hard to get oil that no other bike the shop sells uses. I can guarantee you it's the same for gear oil, the dealer will use whatever is the nearest grade unless they have a decent requirement. But let the navel gazing continue, it's fairly amusing.

   
Ciao

[Huzo]

On a Carc bike the biggest worry you have is the pinion nut hasn't loosened of as they are lightly torqued from the factory without thread locker (Roper info) and when the lock washer lets them back off it destroys the Carc, not the absolute precise grade of gear oil you use.

Nah...Bullshit.
That can’t be right...!




Something that bad would NEVER happen to my bike...

[lucky phil]

Nah...Bullshit.
That can’t be right...!




Something that bad would NEVER happen to my bike...

You've obviously been half a grade out in the gear oil you've been using, lol.

Ciao

[Huzo]

You've obviously been half a grade out in the gear oil you've been using, lol.

Ciao

The nut came loose..!

[lucky phil]

The nut came loose..!

I know.

Ciao

[Philnewbike]

You've obviously been half a grade out in the gear oil you've been using, lol.

Ciao

Should have used ATF fluid !

[Philnewbike]

On a Carc bike the biggest worry you have is the pinion nut hasn't loosened of as they are lightly torqued from the factory without thread locker (Roper info) and when the lock washer lets them back off it destroys the Carc, not the absolute precise grade of gear oil you use.

How many CARCs have failed that way compared to not using the right EP grade oil though? I'd bet not using EP is far more common, but we'll never know.

Here's another fact of life in cars and bikes. A significant amount of the time even the official dealer servicing DOESN'T use the grade of oil specified,if it's an unusual grade they dont normally carry or isn't used in their shop. I know this for a fact as I've seen the receipts for the oil used from a dealer service with the wrong grade of oil that was used on the servicing receipt many times. Plus of course from friends in the industry that service bikes. Manufacturers know this sort of thing happens and by and large engineer their products to tolerate this. They obviously make a requirement but are usually smart enough to have enough "head room" in the design to allow for deviations. I think there'd be quite a few Griso's running around happily on 15W-50 or 10W-50 instead of the 10W-60 hard to get oil that no other bike the shop sells uses. I can guarantee you it's the same for gear oil, the dealer will use whatever is the nearest grade unless they have a decent requirement. But let the navel gazing continue, it's fairly amusing.

Viscosity at 100°C engine operating temp:
15W50 Motul 138.7 mm²/s
10W60 Motul 156.1 mm²/s

Viscosity at 40C gearbox operating temp:
Agip 85W90 206 mm²/s
Redline 75W90 100 mm²/s
Redline 75w140 175 mm²/s - looks ok

I agree to some extent. But 15W50 and 10W60 are very similar viscosity a the operating temperature of the engine. 85W90 is the gearbox spec for my bike and Redline 75W90 is nowhere near the spec, not just a bit off, it's in another ballpark in terms of viscosity at the likely operating temperature: it is about half the viscosity - I thought that, considering it was recommended by Opie, was pretty interesting in a Navally kinda way  . Glad you enjoy the oil thread, I love em, most don't.    75W140 looks ok for gearbox but is a rather expensive experiment imho. Oh, and far too viscous for the final drive

Don't get me started on using ATF. Jees, you may as well use olive oil (extra virgin with molyslip, obviously  )

[TheHungarian]

The gearbox on my V7, running the stock oil, sounded and felt like a load of bricks in a cement mixer. I switched to Bel-Ray Big Twin Gear Oil 85w-140. Now it sounds and feels like a load of river stone in a blender.  Shrugs.   

Best,
Mike

[Gunnar#1]

I know this is an old thread BUT I just got a Stelvio and her in the Arizona desert at 95 degrees the CARC Wass to hot to hold my hand on for more than a second or two.

[Mr Revhead]

The viscosity is just one part of the equation. And to be honest in a final drive or Guzzi gearbox not that important. There isn't many tight bearing surfaces or oil gallery's for it to go through.

What is important is the spec of the oil and film strength.
I am surprised to see GL4 species for a final drives. Its usually gl5 which has a higher EP spec.

[Old Jock]

Do the CARC bikes have any yellow metals in the gbx or bevel box?

That's usually the reason GL5 isn't specified AFAIK

That said there are quite a few oils whose spec sheets state they meet GL5 but are not aggresive to yellow metals

[pressureangle]

Here in the U.S., after a similar amount of homework I've chosen Chevron Delo ESI 85-140. It exceeds all the OEM specs by a wide margin; the only question unanswered is how long it takes to react with the humidity, as it's mentioned in the literature. I moved away from RedLine as it's so sticky it interferes with inspection and requires a rinse at changes.

[Stretch]

Interesting discussion.

My auto parts store was out of 80W90, so I put 75W90 in the gearbox.
Valvoline synthetic, I think.

I'll do the same in the final drive. 75W might actually be a slight advantage in cool
weather like we get in Maine.

FWIW, I suspect that you could use almost anything in the gearbox. 10w50, 85W90,
or even ATF. I've owned vehicles specing(sp?) all of those for a manual gearbox.
Change it when you change the engine oil every 5K and it'll probably outlast the rest
of the bike.....

It seems that shearing forces on the oil would be particularly hard on the final drive
oil. There's an awful lot of force on that pinion! So, it's probably a good idea to stick
to gear oil there. 75W90 vs. 80W90? Not an awful lot to choose there, especially if
one changes it at every tire change. Service interval is 30K, so 75W90 should be fine
every 6K to 10K miles.

YMMV.     

                                               -Stretch

[Huzo]

When you sit and stare at the CARC on your 200,000 km Norge and you are as far geographically from home as it’s possible to get…
You think of Roper, Michael and the Motul that you’ve put in there from day dot…
100,000 European kilometres, 100,000 Australian kilometres, hundreds of Alpine passes and 42 deg C Australian crossings.
Then you wonder if you should change what you’ve been doing…
Do ya’ feel lucky..?
Well, do ya’….punk ?

[moto-uno]

   +1  . Peter

[rocker59]

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.

75w90.  I think you may need to re-read what the numbers stand for and mean. 

The "w" stands for "winter".  75w is the oil's characteristic at 0-degrees Fahrenheit.  Not many of us begin our rides at that temp, so it's a bit of a moot point.  Most of us don't start a ride at 0-F, and if for some reason we did, the bevel box and transmission would quickly warm to operating temps after a few miles.   

As you mentioned, the 90 number is the oil's characteristic at 100-degrees Celsius.  No, most of us don't ride at that air temperature, but the oils inside our motorcycles can certainly see that temp.  100-C = 212-F, or the boiling point of water.  I think if you would take the trouble to check your Engine, Transmission, Bevel Box oil temperatures after a good ride, you might be surprised at those oils' temperatures.  They'll be warmer than you think.

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.
 

No one has done that.  Not even the factory!  But many of us have run the same oil for hundreds of thousands of miles over multiple bikes.  My choice is Mobil-1 75w90 synthetic gear oil for engine and transmission on the Guzzis I've owned, and it's served me well.

[Mr Revhead]

Oil threads are funny. So many people determined to comment when really they actually know next to nothing about how oil works.
Viscosity is not a key factor in things like gearboxes. The spec of the oil (addives for shear, film strength and EP protection etc) is the vital thing.
Viscosity comes into play when you need to pump it through small holes or clearances.

[rocker59]

Oil threads are funny.

They are. As are the wackadoodles, waxing on ad nauseam.

 

[bacongrease]

Oil threads are funny. So many people determined to comment when really they actually know next to nothing about how oil works.
Viscosity is not a key factor in things like gearboxes. The spec of the oil (addives for shear, film strength and EP protection etc) is the vital thing.
Viscosity comes into play when you need to pump it through small holes or clearances.

   FYI......whatever.   



 
 A riding buddy " Indian Chief" drives semis.  When he bought his first one, he drove it for a week and went to change the fluids. The only oil that came out was engine oil.  Not a drop in the rear ends.?  He was hauling dirt IIRC. So doing a lot of shifting.   


Edit:    I should mention he added fluids And carried   on. That was about 5 yrs ago. No harm was done. ? Still driving it daily,