This is admittedly a dumb question and I dont think there is any problem, but I figured I'd ask the experts here anyway...

I just replaced the gear oil in the rear diff. Manual calls for 80w-90. I knew I had one qt of gear oil already at home so when I went to the store I just picked up one more. After filling with both, I realized that the one I had at home was 85W-90. So I mixed 80w-90 and 85w-90. Did I cause any problems, performance related or otherwise? Especially since the manual calls for all 80w-90.

 

Dude. You better drain that ASAP! The difference in weights can cause unbalanced pressure between the molecules in the oil, causing it to degrade the gears and other metal parts 10x faster!







Not really
Its fine. Dont worry about it

Its essentially now an 82.5w-90

 

You even had me goin, good one

 

I didn't fall for it, but you get an A for the effort!

 

I try my best

I mix engine oil weights all the time...and gear oil weights. and conventional and synthetic....
Why?
Sometimes its necessary, sometimes Im lazy...sometimes I'm too broke to get synthetic, or a new bottle of gear oil...