Oh goodie... more oil wars!
Shell Rotella T Synthetic 5W40 is manufactured specifically for the diesel engine market, but the container label states it is "suitable" for use in gasoline engines. Although it may be suitable for use in gasoline engines, this is a diesel engine oil specifically formulated to handle the shear forces of diesel engines.
I think you're getting two different additive packages mixed up. One set of additives is specifically included to reduce oil break down due to shear forces. Another set of additives is included to reduce internal engine friction -- so-called "friction modifiers."
Manufacturers of motorcycle-specific oils (and oils forumulated for diesel engines) say these special oils contain additives that guard against breakdown of the oil due to shear forces. Here's how:
An ordinary multi-grade automotive oil -- say 5W40 -- is a base 5 weight oil when cold. That's a pretty thin oil. When it gets hot, however, it becomes the equivalent of a 40 weight oil. How does it do that? I'm glad you asked!
Modern multi-weight oils contain special polymers that change shape with heat. When they get hot, they elongate affecting the viscosity of the oil -- in simple terms it becomes relatively thicker. So what does that have to do with the price of tea in China? Well, over time, shear forces inside the engine can break these elongated polymers into smaller pieces. When that happens, the smaller pieces of the broken polymers can no longer affect the oil's viscosity the way they did when they were longer, and the oil's viscosity decreases -- it becomes relatively thinner.
Manufacturers of motorcyle-specific oils claim their oils are resistant to breakdown of this sort. In fact, resistance to breakdown is one of the main marketing points for motorcycle-specific oils. But there is credible evidence suggesting there might be a lot more marketing than science in these claims.
You might start here if you're inclined to a little research helping separate the facts from the hype. You'll want to carefully read results 4 and 5 of the section titled "Preliminary Conclusions."
The fact is, oil DOES break down. In fact, a fresh multi-grade oil with a 5W40 rating may only be a 5W20 after 3,000 miles of use -- that's one of the reasons you should change the oil at the recommended interval. In fact, many manufacturers resisted the push to switch to multi-grade oils when they first became available -- a good single-grade oil DOES NOT break down due to shear forces because there are no polymers to break. Of course, there a number of other major benefits provided by multi-weight oils that outweigh (ha! I made funny!) this singular strength, especially since a simple oil change, which you must do anyway for other reasons, returns your multi-grade oil back to its full potential. But I digress...
The other additive you mentioned was friction modifiers. Friction modifiers are added to gasoline-engine oils (automotive gasoline-engine only, not motorcycle or diesel) to reduce internal engine friction. These additives are aimed at increasing fuel mileage and have nothing to due with preventing break down due to shear forces. Motorcycle manufacturers learned when these types of oils became available that the friction modifiers can interfere with clutch operation, and so recommended their customers avoid them.
API
SL (and earlier)
gasoline-engine oils may or may not contain friction modifiers. Those that do are labeled as "Energy Conserving." All API
SM gasoline-engine oils 30 weight and below automatically contain friction modifiers as part of the new SM standard regardless of how they are labeled (heavier weight API SM oils may or may not). This change to the SM standard (the automatic inclusion of friction modifiers) is why BRP specifically warns against the use of API SM rated oils.
As I mentioned, motorcycle-specific oils do not contain these friction modifiers --
and neither does Shell Rotella T Synthetic 5W40,
despite its API SM rating. To put it another way, since they are not specifically intended for use in gasoline engines, there is no requirement for oils marketed for diesel engines to add friction modifiers in order to meet the API SM standard.
In short, since Shell Rotella T Synthetic meets BRP viscosity specifications, is purportedly shear stable like motorcycle-specific oil and DOES NOT contain friction modifiers, I believe it is perfectly suitable for use in your Spyder's engine. I've been using it in our Spyder for 3,000+ miles with no clutch issues. In fact, I've used Shell Synthetic oil in ALL my motorcycles for years (10,000+ miles on my Triumph Tiger 1050) with no clutch issues.
As I mentioned in an earlier post, with an oil change interval of only 3,000 miles, you could probably use vegatable oil with no problems in the Spyder...
Although there is a specific prohibition regarding towing in the Spyder Operator's Guide, there is no detail explaining why (dangerous handling qualities, possible clutch problems, excessive wear on the engine, all of the above, none of the above). Let's wait until we get DATA about Lamonster's clutch before we start making guesses as to what caused it to slip.
Regards,
Mark
My dealer used Spectro brand oil on my first service and I've used it on the two oil changes that I've done. They use Spectro Blue, non-synthetic, but I believe it comes in 5W-40. Their reasoning for using Spectro oils is that they have used it for years in many high performance engines and it hasn't failed them yet AND it is cheaper than the BRP oil.
