Reduced mileage after oil change

Anyone notice any reduced mileage after front/rear differential and transfer case oil change?

I notice I get 1 to 2 mpg reduction.

I drive the same path and drive the same style and distance from my house to Flagstaff, Az and notice the difference.

 

In my pea brain, that doesn't seem possible. Unless the oil in each was to get contaminated in some way that would lower the viscosity.

 

not sure it 's possible...???

 

Lol

 

How exactly are you measuring this?

 

What year? Mileage? Did you do anything else while performing the maintenance?

 

Nope. Just drive it.

 

Mine improved. Seriously, I can’t prove it.

 

What weight gear oil do you use?

 

I just did all the gear boxes this year at 25k miles. A little early but it fit my schedule.

 

I drive the same distance and same speeds 75 to 78 mph all highway.

To those with other questions:
2020 TRD ORP
30K miles when I changed front and rear diff and transfer case.
I used Redline 75W-85 on differentials and Valvoline 75W-90 on the ttansfer case.

 

When I did mine at 95k (unknown if it had been done before), I DID seem to have a slight drop. Not as dramatic as 1-2, it was more like .5mpg. I used off the shelf oil that was slightly thicker than the OEM stuff, I attributed it to that.

 

I did mine at 105k. I checked and couldn’t find it had been done before. I did not have any decrease in mpg. I used Amsoil for the diffs and used

$20 Royal Purple 01300 Max Gear 75W-90 High Performance Synthetic Automotive Gear Oil , 1 Quart (32 Ounces)

Royal Purple Max Gear 75W-90 High Performance Synthetic Automotive Gear Oil in the transfer case.

 

Ok guys, I jut made a fool of myself.

I just realized (forgot), I have 4 new KO2 tires which are 6 ply, and they are heavier than the original tires.

 

That's probably the culprit.

 

That'll do it!

 

Mystery solved. I love it when they are that easy.