I recently changed all fluids in the truck to Royal Purple synthetics, motor, trans, transfer case, and both diffs. With my old oil, non-synthetic Rotella in the engine, I made a trip from Fairfax to Richmond, Va and hand calculated mpg. Each trip was around 260 miles round trip, unloaded both times.

I made the same trip with all fluids changed to RP and seen a 1.9mpg increase. Both trips were at night, about same temps, no rain. Wind may have had a little to do with it, but from what I remember it seemed about the same.

Has anyone had similar experiences? Does this sound accurate? I'm just tickled my mpg's are in the 18's...

 

maybe I should switch, just tanked up today, 26 gallons, 334 miles........ that is if I have my rpmile right, sure seems correct but never checked w/ gps I think hte tech was in a different area than most do the tire size rpmile thing, 704 seems right on the money checked via mile markers and odom. over a ten mile course. Purple has me thinkin as my mileage was in the mid 13's, driven empty.

 

I put Rp in everything but the trans(warranty issues) I think I did pick up some mileage with it. I can't tell for sure because I put the fluid in and grossed 18000#total from AK to Fla. since then I get 15-17 mpgs around town. this is with 400+ hp, 4.10 gears and 35" tires.

 

DR3500 what kind of warranty issues

 

If I put RP in the tranny and later on have a problem with the tranny the dealer will void the warranty on it if it doesn't have the factory type of oil in it. They take a sample while they are draining it and have it tested.

 

You should see the same type of increase with any good synthetic fluid, well at least with AMSOIL I did.
As far as the tranny oil, yo can fight that one because DC is the only place that yo can get 100% certified ATF+4. Last time I checked it was against the law for them to require yo to run a fluid that was not available over the counter, if they do then they have to provide it for free

 

I used RP on my last cummins and also experienced better mileage. I also use it in all the bikes we work on. Great results!!

 

Are you putting the Synthetic in the motor, or just the diffs/tranny? If in the motor are you still changing at 7500 intervals? I personally won't put anything but ATF+4 in the tranny.
DK

 

ditto 1 mpg gainded by changing rear axle fluid only,,,,

 

I did the whole she-bang!

 

Actualy you can go at least 3 times the oil change interval with syn oil.

 

THe 6 spd NV5600 doesn't use ATF...it uses Pennzoil/Quakerstate Synchomesh fluid. The Royal Purple, even though RP says it does, doesn't meet the DC specs. You have to look at the specs. Redline MTL and the new Amsoil MTL meets the DC specs. I used Redline MTL in my truck and never had any problems. Changed everything underneath every 15k.

 

I emailed royal purple about 6 months ago and asked if their tranny fluid will work, and the response that I got was a yes. The guy who emailed me actually had an 03 dodge with a cummins and 48re that he had personally run it in. That is the last fluid that I have to switch over. I am not really worried about my warranty...see my sig. Tranny warrant is long gone

Brad