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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 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
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
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 sharingSkippy
I would need to see more pants suspenders and corn cob pipe smoking first.This is what I removed.
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
Fuchs/Silkoline GL4 80w90.
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.
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.
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
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.
Most on here who run Redline use the Heavy not the LightWith the older 5 speeders the majority of the gears are Helical not straight cut.