Quote:
Originally Posted by CZroe
Not unless it's motorcycle-specific. The diesel stuff we often use is no 10w40 and the car 10w40 synths all have friction modifiers added that are bad for the wet clutch.
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Not sure what you mean by that, but I guess you are missing a "t".
Rotella T is a 15W-40, so I think that's what you are getting at. A 15W conventional is only a good choice if the temperatures are always above 50 degrees when you start-up. If you start in lower temps a 10W (minimum) or 5W (better) synthetic provides much better lubrication.
Diesel oils like Rotella and Delvac are fine for a cycle. Auto oils like Syntec or Platinum are not, BUT, it's not just an issue of Friction Modifiers.
Friction Modifiers are not added to auto oils in the 40-grade range and above (usually 10W-40) - just 30-grade and below.
The
real issue for cycle use is the low levels of ZDDP that are mandated for current auto oil. ZDDP is an additive that protects the valvetrain from damage before adequate oil arrives - like starts. Current auto engines get around that with roller rockers and lifters. Cycle engines (except the CBR250R) use solid (non-roller) valvetrain components that need higher levels of ZDDP to prevent damage.
Diesel oils are not required to have the same low levels as auto oils, so they have adequate amounts of ZDDP for a typical cycle engine, and are a good low cost alternative.
Cycle specific oils are the best choice, and usually have even more ZDDP, but for all but the most extreme conditions a quality diesel oil will be more than adequate.