I spoke to a Mobil tech recently and he admitted that many folks were using the recap in their Harley primary drives without slippage.
What he did tell me was that Mobil 1 redcap 15W50 has more FM's than it used to. So many folks who had been using it successfully in years past might now develop a problem; I don't know.
For what it's worth, I put over 300 miles on my '94 Low Rider with the redcap in the chain case and never noticed any slippage at all. And that was done in the last month, so the redcap had to be current production.
I think the clutch slippage thing is over-stated in many cases, likely by folks who are selling dedicated motorcycle oil at double the price. I'm not saying it doesn't happen, I'm just saying that it isn't as common as some folks would have you believe.
When I drained the dino-Harley oil from the chain case to put the redcap in, the dino oil wasn't very dirty (with over 2000 miles on it).
I got paranoid about the redcap in the primary after doing some reading (yeah, I know, I shouldn't believe everything I read) and I drained it and replaced it with the Harley dino (primary chain specific, overpriced 10W40 motor oil
). The redcap emerged from the primary looking pretty soiled, with much "debris" in suspension. It appeared to have cleaned up the dino oil's mess. The bike had been run over 13,000 miles (regular changes, of course) with the Harley dino stuff in the chain case.
After a short while I'll probably drain the Harley oil and replace it with a synthetic 10W40 with a moderate or low FM number (if I can find such). I believe that the drive chain will benefit from a lower viscosity oil for better penetration of the chain links. The 20W50 will work; I just think that the 10W40 will be better. The Mobil 1 tech I spoke with recently agreed that a 10W40 oil would be the best choice for the primary drive.
I don't get all the hoopla about the "three in one" oil. It's largely a convienience issue and less so a matter of best oil in each spot. I think the 20W50 is probably a compromise for the primary and the tranny. Mobil 1 and Amsoil both are just responding to Harley Syn3 with the recommendation for an all around oil.
I came away from my extended conversation with the Mobil tech with the knowledge that 75W90 Mobil 1 gear oil will take better care of the tranny than any lighter oil can, and that 15W50 redcap (at half the cost of the Vtwin oil) will be more than enough protection for the crankcase.
One of the Harley Davidson's advantages over other designs is that you can actually be "lube specific" with your tranny, crank, and primary oils. Why throw this inherent advantage to the wind and use the same oil in all three locations?
There have been dozens and dozens of Harley evo's pass 100,000 miles without a tear down being necessary--and most of these were done using the Harley dino 20W50 oil. With a better oil, such as the redcap, engine life could be extended even further.
There is currently an '87 RK in Western North Carolina with over 400,000 miles on that engine WITHOUT A TEARDOWN. The rider has maintained it with dino Harley oil and regular changes. Harley has made him an offer of a new bike of his choice as they want to inspect the engine in Milwaukee--and likely put the bike in their museum. So if that bike can go that far with the Harley (read Sunoco, now probably Citgo) 20W50 oil I think we can relax a bit with regard to engine life when we use the superior synthetics...
Dan
