75W-90 vs 80W-90 gear oil difference?

[Andy G]

So I'm changing the fluids on my '02 Trooper and the manual says to use 80W-90 GL-5 LSD in the rear, and 75W-90 up front. However, I can get it cheaper if I run the same front and rear, and am wondering if it's safe to do so?

I'm a big Lucas Oil fan and they offer a dino 80W-90 and a 85W-140...or they have a synthetic 75W-90 and a 75W-140.

Is it okay to run their 75W-90 synthetic front and rear, even though they spec 80W-90 back there?

EDIT TO ADD: I live in Michigan...the high yesterday was 7F...so I need something that's gonna run well in both cold and 95F in the summer.

Thanks!
Andy

 

[Saints&Sailors]

The key is having the LSD additive in the gear oil and it being the proper rating (in your case, GL-5). 75w-90 and 80w-90 are very similar oil weights. In fact, depending on the brands of oil, something marketed as one weight can actually have specs closer to the other weight and vice versa. If you have a LSD, make sure you have the additives in your gear oil or pick up some additives to add to your differential if the gear oil doesn't already contain it.

I've used Lucas oil before in my Jeep's axles. They appear to make decent oil although I'm not sure how much "better" it is than any other brand.

 

[Andy G]

That's what I figured it was, wasn't 100% sure though. Thank you!

The key is having the LSD additive in the gear oil and it being the proper rating (in your case, GL-5). 75w-90 and 80w-90 are very similar oil weights. In fact, depending on the brands of oil, something marketed as one weight can actually have specs closer to the other weight and vice versa. If you have a LSD, make sure you have the additives in your gear oil or pick up some additives to add to your differential if the gear oil doesn't already contain it.

I've used Lucas oil before in my Jeep's axles. They appear to make decent oil although I'm not sure how much "better" it is than any other brand.