Originally Posted by NinerBikes
Perhaps one more reason to use unleaded fuel and a full synthetic motor oil in your Rotax equipped RV-12. Full synthetic motor oil is much, much more resistant to breakdown.
Expiration dates can be a funny thing. Do the ADDITIVES in synthetic oil break down over time, I think the answer is clearly, they do ... which is why Shell marks the bottles with an expiration date. This is one of the reasons I order my oil 3 bottles at a time a little prior to needing it, as opposed to purchasing a case at a time ... with the clock ticking while the oil sits in the box at the hangar. Would you trust your $25K engine on oil 2 years past the expiration date set by the manufacturer? .... I wouldn't. If I flew a bunch, I would feel OK pushing it a little and using oil just a few months past the expiration date knowing it will be changed out in a few weeks anyway, But if that next oil change is a year away ... no way.
I think most would agree if we ONLY run unleaded fuel, a full synthetic motorcycle oil is probably preferable to a semi-synthetic blend. In fact, prior to the partnership between Shell and Rotax, motorcycle oils were on the Rotax approved oil list. However, I would ONLY use a full synthetic that is formulated for motorcycles. The clutch in the gear reduction unit has already been mentioned in a previous post but, more importantly, it is my understanding that motorcycle oils are also specially formulated to resist shearing at the molecular level which is caused by the gears in the motorcycle's transmission under high loads ... or in our case, the gearbox for the prop.
Having said that, if I knew I was going to leave my area and will be fueling with 100LL during the trip, I would make it a point to run Shell Sport 4 for the trip ... as opposed to a full synthetic which has very poor lead suspension characteristics, which for me a no-go with 100LL.
My 2 Lincolns.