Thanks for the video that is damn impressive. 550 degree temps in the engine which are double what you would normally see and the oil held up enough that it could be reused.

It would be interesting to see the same test run on other oils just to see what the difference would be

 

I am a fan of Rotella 15W40 in the primary.

 

I've had luck with Mobil 1 and it's what my guy recommends and uses in his. I totally trust this guy as I used to work with him and know him personally.
I have not had a need to change primary and tranny in less than the 10k.

Of course more often won't hurt anything, and at the very least the condition should be checked and go forward from there. Yes I agree with what someone else said about not going from brand to brand. They each have their own additives that may or may not play well with each other.

 

+1. Just as I did with my evo, 1 qt Rotella T and top it of with Lucas oil stabilizer. Less clunk and no clutch drag when cold starting in gear with clutch pulled in.

I just got a clutch recall in the mail, so maybe that's causing the cold start drag, but it's much less noticeable with Rotella T.

 

Just to update... My original assessment of ATF in the primary may be a bit premature. It was a warm day, near 90 degrees and I went out at lunch today and started practicing slow speed motor officer exercises in a parking lot. Didn't work out too well, my friction zone was gone, slipping the clutch was a jerky mess. Riding trying to slip the clutch in 2nd gear around corners gave clutch chattering and jerkiness, you could feel the clunk when upshifting. When I got back to the office I removed my earplugs with the bike still running and the primary sounded like it was filled with rabid weasels with power tools running wild. Not exactly what I want

Rode her home and dropped the primary fluid and replaced it with SAE 50 VR1 then headed back out. Slow speed exercises were precise, no clutch jerkiness, smooth and fluid with a great friction zone; no noise beyond the typical HD primary sounds, no clunking into gear or changing gears... butter as she always was

I guess the uptake is, if I can't be a good example at least I can be a terrible warning; don't waste your time playing with ATF, stick with the heavy fluids like SAE 50 VR1 or Formula + in the primary...

 

Just changed the tranny fluid on my Silverado for the first time. It had 150,000 miles

 

I had my oil analyzed. The analyst recommended doing the tranny about every 15k. Engine and primary every 5k. At 5k, my trans looked clear like vegetable oil.

 

How is the VR1 50 working out?

 

I love that stuff! I run the VR1 SAE 50 in the engine as well, the extra zinc/phosphorus content is just what these air cooled push rod engines need, and the VR1 in the primary is just butter smooth. Formula + which so many swear by for the newer Twin Cam primary is really nothing but an overpriced 50 weight mineral oil with a few pressure and anti-foam additives and I've never been a fan, never had a great friction zone and she always clunked but the VR1 is the best I've found so far for the primary.

The VR1 gives a great friction zone with zero clunking, even on a hot restart; it's doing the job. It's so snicky smooth when shifting it's almost like riding a metric I use the two finger clutch upshift/rev match downshift technique and after experimenting with many different fluids in the primary the VR1 is the best I've found. I'm going to try the VR1 SAE 60 next just to see how it performs in the primary but as of now the VR1 SAE 50 is what I recommend to everyone with a newer Twin Cam, same viscosity as Formula + and it actually works

 

I'm running it in the engine also but think 60 would have been better this summer. I plan on changing the primary this weekend and I have an extra bottle of the 50 on the shelf so I will give it try.