Originally Posted by Madjik_Man
I assume those 2003 specs are the same for my 1998?
Also... can I put 80W-90 in there even though 99.8% of the time it will be above 0 degrees? And just have it in the diffs for those rare times it does get that cold?
Will it have any negative effect?
The specs should be the same for all 1st gens as there was no change in the rear diff over this period.
I'm not an oil expert, and don't have to worry about 0° in coastal California, so I'm sure someone who knows more than me can chime in. I used 75w90 mobil 1 in diffs + transfer; redline for tranny.
Saw this on a different board via google fwiw:
"Owners manuals are very confusing sometimes. Most 75W-90 gear oils are synthetic and most straight weights and 80W-90 gear oils are mineral based. What they are trying to tell you is if the temps are above 0-F you can use a straight 90wt gear oil, but if you are going to see temps below 0-F to use a 80W-90 mineral gear oil. Your 75W-90 gear oils will cover a wider temp range, and will work a lot better in below 0 temps.
A good gear oil to use that you can probably find on the parts shelf of most parts stores in your area would be Mobil 1 75W-90 gear oil. You do not have to add anything to it in case you have a limited slip/posi-track diff."