Quote:
Originally Posted by rcjetn
Megadan: Bought Rotella T4 15w-40 like you suggested. The container says it's for diesel engines ?????
Jack
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And?
Let me put it to you this way. Diesel engines require 4 key things from their oil.
1. High heat resistance - diesels under load are insanely hot, contrary to popular myth, and the oil needs very high thermal stability to resist getting cooked, or thinning out and allowing excessive wear.
2. High shear strength - You often hear "diesels spin slow, unlike a bike engine" blah blah blah. A 3-5lb piston traveling along a 5-7 inch stroke at 2000rpm with a high compression ratio with forced induction creates way more shear force than most typical car engines, and is only really matched by say an engine that turns past 10,000rpm. Diesel oil needs to resist a ton of shearing force
3. High compression resistance - The force applied to the bearing surfaces of an engine compressing the intake charge to many thousands of PSI, and then making it explode is immense, and the typical gear drives found for the fuel and other systems are also very hard on oils, often breaking down at a molecular level. Diesel oil needs to resist these forces to prevent metal to metal contact and for longer service life.
4. High detergency for particulate suspension. - A common fact of life with diesels is that they are dirty, and their blowby puts a lot of carbon in the oil. To combat this the oil needs to be able to suspend the particulates in order to pass them through the filters and prevent them from building up an settling in places that can cause issues down the road.
How does this apply to motorcycle like ours?
1. An aircooled engine such as these runs hotter than a typical liquid cooled engine, thus a high thermal stability is necessary.
2. The higher RPM nature of the engine means that the oil needs to have a high shear resistance to protect the rings and cylinder.
3. The oil shares itself between the engine and the gearbox, and the gearbox is a gear drive where high compression resistance is important for longer service life
4. A bike with a wet clutch puts organic material into the oil that needs to be suspended to prevent it from settling.
All 4 of these traits are also common among motorcycle specific 4T oil.
Rotella also has a high ZDDP level, which is beneficial to a flat tappet valvetrain as found in our CG clones to reduce wear on the cam and followers. It is also wet clutch rated JASO MA2.
I am not endorsing Rotella as the best oil in the world, but short of a high output high RPM modern precision machine, it is way more than adequate for these bikes. It's a very popular oil in the 4 cylinder Goldwing community where guys like me would put tens of thousands of miles on our bikes. For contrast, and just to make a point, I run Motul 7100 synthetic in my VFR1200
Run whatever oil you want to run, but don't think that any harm will come to your engine either. More wear and damage is done due to cold startups and revving the engine before it is up to temp than almost anything else. The number two cause for accelerated wear is improper oil change intervals. As the saying goes, the best oil is clean oil.
If it makes you feel better there are several of us that have put thousands of miles on our Hawks and other bikes that run Rotella oil. Myself and others do so using Rotella oil that push them pretty hard for extended periods of time and otherwise ride the snot out of them with zero issues. Oil snobs and people who claim to be experts can state "It's not motorcycle oil, so its bad and wrong" all they want, but in my life I have logged tens of thousands of miles between three bikes that specifically only used Rotella T4 or T6, and I never had a loss in compression, bearing failure, oil burning, leaking, or other calamity occour. What I did do was change the oil on a regular schedule based on its smell (fuel saturation), color, feel (loss of lubricity you can feel), or length of time (because oil oxidizes even when you aren't running the engine and breaks down).
If after all that, the little voice in your head still doesn't think it is the right oil to run, no biggie, I wont judge you for it at all. There are plenty of reasonably priced quality 4T oils out there as well.