Royal Purple 85w140 vs. 75w140

[ROADWARRIOR]

Will the 85w140 help the Dana 80 live a longer life and at what cost in fuel mileage?



Thanks,

Dan

 

[GAmes]

I mix them because when I do oil changes the NAPA here never has 7 quarts of one or the other. I'd prefer the 85W140. What makes you think there would be a mileage penalty?

 

[MA2LA]

In some cases a heavier oil can cause drag and thus miliage but don't think it will change much in our case

 

[AFoulk]

I ran the 75w-140 in my jeep wrangler, and even in that,I didnt' notice a difference in fuel mileage from the factory stuff.

 

[rweis]

I've run 75-140 for 70k miles.



I had the 3. 54 changed to 4. 10 and the rear end was extremely clean. I have never read that one (75 vs 85) had any significant value over the other.



Bob Weis

 

[steved]

I'm running 85w140 in my 11. 50AAM and saw no decrease in mileage... may have actually seen an increase in mileage because the 75w90 Mobile 1 appeared burnt/sheared.

The pinion is flooded with oil, as are the carrier bearings... not like the thicker oil is going to starve anything... I have 50k on RP 85w140, with some being in -20*F...

steved

 

[Matt42]

Per the 1996 TSM for severe use, I use 75W-90 in the front axle and 85W140 in the back. It's Royal Purple, and I use the MoPar LSD additive in back, though it may not be needed. Phoenix driving is severe service. In less beastly-hot areas, the lighter oil may be fine. It's supposed to cool down to 110* today.