I have a couple of gallons of Mobil1 10W40 sitting in my garage that were intended to be used on Kaw I no longer own. Not suitable for the Mustang, 5W20, or the diesel pickup, so I figured it would work in the primary of the HD. It's the good stuff, safe for clutches. I realize it's probably overkill using synthetic, but it's in the garage and already paid for. Seems a waste to use it inn the lawn mower or generator.

 

Not if you want to increase the engine life by doing regular maintenance.

 

Run 10w-40 dino in mine. Synthetic is indeed overkill, but yours is 'free.' Heck Yes!

 

I have Mobil one 10w40 v-twin oil in my primary. The clutch works great and I figure the synthetic oil is good for the chain, bearings and adjuster shoe. It will also not break down from high temps as fast as dyno oil. It is connected to a very hot running air cooled engine. I just figure if synyhetics are availabe for the application, why not give my ride the better fluid. Just my two cents.

 

Not good for air cooled stationary engines. A straight 30w would be better in lawn mowers and generators. I would use it in the primary too

 

The manuals of All my 4 stroke air cooled lawn equipment motors say a multigrade synthetic 10w30 is fine. I can't imagine a 10 w 40 not working, expecially in our 100 plus heat.

Beary

 

I run used 20/50 In my mower. I use the Mobil 10/40 in primary.

 

Bike and Diesel 10W40 is ok for Primary. Auto 10W40 has friction modifiers that cause slippery slip clutch engagement as well as having lower base metals which provides wear protection. The base metals are lower in auto oil by industry agreement as a way to extend the life of the catalytic converters to the EPA 10 year goal.

 

Are you sure about that? There is no seal on 10w40 that indicates friction modifiers like you see on the 10w30 oil.

Beary

 

I believe Mobil1 10w40T is what Mobil recommends for Harley primaries. I ran Syn3 in mine for 50K miles and prefer it to the Formula+ that's in there now.