10 w 40 non syn or ATF.. save your money .. Mobil 1 v-twin is a big waste for the primary . I just changed to Mobil 1 15w50 from walmart.. Get 5 quarts for A lot cheaper than the v-twin stuff and it works fine in the engine .. After 4 more changes ill get a free one with the extra quart each time..

 

Its what I use and the lighter oil helps to slightly lower the primary temps.

 

I recently gave in and did the switch to Type-F ATF. Nice smooth engagement, no slipping. Plus O'Reilly had Valvoline Type-F on sale for around $2.50 per qt IIRC. Can't beat that... I'm sure B&M is good oil, but it's a Type-F ATF (printed on the label) and at about $7 per quart is a little pricey for my application. Formula+ had been working well for me and I had no reason to change other than I just can't leave anything alone and I like saving money when it's practical to do so.

Like others have said, the oil provides lubrication to the chain and a bearing, but it's main function is to keep the clutch pack cool. Just seems like a thinner oil would cool better and still provide adequate lubrication at the same time. WTF do I know though...

 

Don't use the Redline 80 weight in the trans,use the Redline V-Twin it's 90 weight. This is right off Redlines website.

 

Thanks to all for the info. Since the weatherman just forecast 10.3 inches of rain for tomorrow I don't suppose it matters a lot right now anyway. I will drive to the local NAPA or Autozone store tomorrow afternoon & see what they have to offer. Monday & Tuesday are about the same, but Wednesday onward is supposed to be good weather...

 

Might want to take your boat!

 

I use a mix of Formula+ & Rotella 15W-40. My primary takes 38 oz, so it gets a quart of F+ and I make up the difference with Rotella. I've tried several different (and more expensive) oils and this combination gives me the best clutch feel. Many just run straight Rotella, so I may give that a shot next time around.

There are lots of options out there that don't cost $10+ a quart- dino engine oil, Rotella, regular ATF, & Formula+ are just a few. Try different ones & see which gives you the best clutch feel...

 

I've used Syn3 or F+ in the Primary for 40k miles. Until 3.5k miles ago I switched to Rotella.

Clutch action has never been better.

 

I also use the Redline V Twin Primary oil in my primary.

 

Dexron ATF in the primary. Cheap, easy to find, and effective.