This is a spin-off of the excellent post “THE OPTIMAL PERCENTAGE OF RACING ATF IS 65%” authored by Inaccurate.

By not doing due diligence and only reading 30 or so posts of Inaccurate’s post, I decided to give the ATF mixture of Red Line Racing AFT and Z-1 a try.

To cut to the quick…here is the outcome:

The shifts improved immensely, the sloppy slow shifts of the past, were now quick and sharp (but not too sharp). However what I noticed immediately was the drop in MPG. My average MPG (mostly highway) went from 27 mpg to 25 mpg. I verified this over 3 tanks on roughly the same route, under roughly the same weather conditions.

At this point I read deeper into Inaccurate’s detailed post. I discovered the viscosity difference of Red Line’s Racing ATF vs. the Z-1 (and the Castrol IMV) that I was using. Reading further, I also discovered the solution of using a 50%/50% solution of Racing ATF and Lightweight ATF to normalize the viscosity.

After a couple of drain/refills utilizing Red Line Lightweight ATF, I have returned the viscosity close to OEM. The shifts are still quick and sharp and my MPG has returned to normal.

More concerning then the MPG drop, was the fact that a fluid with too high a viscosity might cause oil starvation issues during a cold start @ -20 situation (which we sometimes experience in Minnesota)

My vehicle = 2007 Acura TL Type-S, 84,000 mi

Hopefully someone finds some benefit in this…

Below is the data that I recorded during my experimentations:

 

I can't say I've noticed a drop in highway, but my combined has gone up form 19 to 21. I'm the guy that doesn't go a day without vtec if I can help it.

 

If you’re into the throttle and still getting an increase of 2 MPG…something must be working in your favor!
Are you running the mixture of: 1Qt. Racing ATF + 1Qt Lightweight Racing ATF + 1Qt Redline D4 ATF?

 

^2 bottles type-f, 1 bottle of D4 every oil change.

I also switched from E10 to pure gas so maybe that may factor in.

 

Oh yeah, that definitely accounts for most, if not all, of the MPG improvement. Requiring ethanol in our gasoline was one of the worst decisions our politicians have made in the last 100 years.