synthetic oil

I have a 2002 FLSTC I want to put synthetic oil in my engine,primary and trans. I was going to use Mobil 1 20w50 but all I can find is 15w50, would this be ok?

I would imagine there's hardly any difference between the two, especialy once the bike warms up.

Thanks, I have desided to run the 15w50 in the engine and primary and 80w90 gear lube in my tranny. Thanks again.

I'm not sure I'd throw the motor oil in with the primary. It might be allright but I'd check with someone that knows before hand. It may thicken up a little when it gets hot and possibly affect the clutch/and/or shifting..not an informed opinion but just thinking out loud here.

Thanks for your thoughts, I think I will run HD primary lube just to be on the safe side. I do know that HD says you can run their synthetic 20w50 in the primary but they also say you can run it in your trans, but I don't think thats the best lube out there for the trans. Just my opinion.

I never heard of anyone having a problem with the Mobil 1 15W-50 in their primary, but the possibility is there as the automotive formula has moly in it. Most people I've heard who run it in the primary have claimed the levels aren't high enough to cause problems...of course most of those testimonials aren't running as modified a motor as I am so the clutch isn't worked as hard.

I have run the 15-50 in my motor the last two years and plan to continue. I consider the three seperate compartments for fluids a benefit and add the appropriate specialized oils to each compartment.

Mobil 1

I think you're dead on Seahag regarding the moly in Mo 1. If my memory serves (not as well as it used to) the November American Iron had an article about syn oils. I believe Mo 1 had the highest levels of moly of the oils they compared. Some folks shy away from Mo 1 in the primary because moly is a great anti-friction compound... not ideal for the clutch. If you don't have any problems then this just may be a theory that doesn't hold up. I think they recommended a 10w-40 non-syn because the primary oil serves for heat transfer more so than lube. As for the tranny, I have a hard time seeing my way to 20w-50... to my way of thinking, not enough film strength for the gears. That's my gut and a few "experts" seem to think the same way.