That is what I use, no problems.
Mobil 1 in the engine and Mobil 1 V-Twin in the primary.
I can't say for sure the frictiom modifiers will cause the clutch to slip, but why take a chance for a couple bucks.

 

I'm like you French, I was using Amsoil and switched to Mobil 1 15/50 back in the summer. My engine is quieter! The question I have is about using it in the Primary also.
I also have a question about Mobil 1 Gear oil 75/140 I would like to use one Manufacturer in my bike. Plus I can buy all of it at Advance Auto down the street.

 

I used to use regular Mobil 1 in my bike, then I switched to the Mobil 1 V-Twin just because you could get it in 20W-50. If I remember correctly, couldn't you used to be able to get 20W50 in regular Mobil at one time? It's only over the past decade that they started the V-Twin stuff.
I just did an oil change and used Amsoil. Not only is it WAY more expensive, I'm not really noticing any improvement in temperature or noise. I think I just paid way too much money for oil that does the same thing as Mobil 1 did.

 

Honestly, money was not a factor when I decided to try Mobil1 15W-50 in the primary.
The main reasons were:
1) The Walmart I bought my 15W-50 at didn't carry V-Twin.
2) I tried B&M Trick Shift which, from what I read here, was a great oil for the primary and it didn't work at all in my bike, so I thought the heck with all this marketing hype, let's put the same oil as in the engine and we'll see how it goes.
I can't say I'll continue to use it but so far, it performs very well and like I said, I have experienced no slippage whatsoever.

 

I use Redline with Shockproof in my tranny and don't plan to change. It works great and I love the color! <g>
I don't see why Mobil1 75-140 wouldn't work. Try it and if it doesn't perform to your liking, it's very easy to replace.

 

http://www.mobiloil.com/USA-English/...duct_Guide.pdf

Mobile 15w50 phosphorus ppm 1200 zinc 1300
Mobile v-twin 1600 1700

Looks like 30 % plus difference to me. If you don't know what these do for protecting engine parts do a google search for ZDDP.

 

I run Mobil 1 in about everything 4-stroke I have.

 

I have been using Syn 3 in engine, trans, and primary on both of my bikes. I will be switching to Mobile One V-Twin at the next oil change in the engine and primary, with Redline Shock Proof heavy going into the transmission.

Good friend in the oil biz, sells Mobile products exclusively. Cost on oil is never an issue and he emphatically states the V-Twin product is best for Harley applications.

Note, this is not sales hype as he isn't selling me the product or profiting in any way from my using it.

 

I was just reading an article on Harley oils in American Iron from a couple of months ago. It implied that the moly content was an important feature, that raised the price of the oil and only 3 of the top oils they tested had it (HD oil did not).

If the car oil is both cheaper and has higher moly content, I'd be interested.

 

I dont understand this as according to the chart the oils with the lower zinc and phosphorus ppm are "Boosted, fully synthetic formula designed for todays longer oil change intervals" where the V-Twin ppm higher levels of the same are designed where clutch lubrication is also important. So why the need for higher levels if its not lubricating the clutch