Imastang

So I finally got all the fluids switched over to Royal Purple
Engine - 5W 20
Transmission - XPR 5W 30 Racing Fluid
Differential - Max Gear 75 - 140

I am seeing an additional 3 - 4 miles per gallon more.
I thought I would mention - I have seen some post that they are using the Synchromesh version (ATF) but I quized the RP technicians on this (3 times I might add) and after giving them the codes from the mamual they recommended the racing fluid for the transmission - Shifts good and everything runs smooth.

For those of you who are more mechanically enclined - what harm is there in running the ATF fluid vs the fluid RP recommended?

Snakebite64

A question if I may, why would you see such a large improvement in your mpg and I can assume all syn oil would see the same improvement.

AzPete

The mpg improvement supposedly comes with changing all the fluids to the synthetic breeds.

I would say as long as the RP product meets or exceeds the Ford recommendations you should be ok.

Imastang

I talked with Royal Purple today told them I was not completly satsified with the performance of the fluid for the transmission so they are sending me the Synchromax free of charge to replace the racing fluid - I will let you know how much difference there is when I get it swapped out.

AzPete

What was the problem with the tranny fluid?

Swoope

xpr is a motor oil designed for racing.

http://www.royalpurple.com/xpr-racing-oil-r.html

what you are doing with it in your tranny is killing it.. syncnromesh is not the answer either..

i have used rp in my track cars in the past.. good stuff, but you have to use it in the right places.. if royal purple gave you those recommendations i would be shocked.. but if you did not look it up on your own, shame on you..

i know ford is going to end up paying for your failed transmission fluid change, but karma is a bitch...

maybe you should just leave well enough alone and let the dealer do it.. btw you mpg change is a folly..

beers

Mishri

and to think... ford could increase their cafe rating by just putting synthetic fluids in the car, bought in massive bulk quantities probably only costing $100 per car.. instead of billions in R&D.

yeah i don't buy it.. i think you guys delude yourself, it takes a very controlled environment to determine mpg changes in the 10%-15% change range you are talking about. If synthetic fluids put your mustang GT over 30mpg hwy Ford would be able to brag they have a 30mpg+ v8, the only kind in it's class.

Snakebite64

^^^I thought 3-4 was way high and all major brand syn oil should be able to do the same no

Imastang

So - Yes I looked up the numbers in the owners manual - based on the numbers and the reference chart on the website the recommendation is the XPR fluid - They actually state 10w 40 - but this stuff is suppose to be better.
So far the transmission is working great - no worse than what it was - I am mearly trying to reduce some of the notchyness between shifts (As others have mentioned)

Seeing how this fluid reduces heat and friction can not see how it will mess up the transmission.

On the MPG - I am only reporting what the car is saying when I am driving it. I never stated it was getting over 30mpg (Yes that would be awesome but know that is not happening) I am seeing 22 - 23.5 mpg which I think is very good.

JAJ

Ford's stock diff and transmission fluids are synthetic already. Why would you expect to do better?