My 98' TA has 125,000+ and i never have to add any! I have never had any problem with it. I don't think that we have had any trouble with my buddies 98' z28 either and we drive pretty hard.

 

1/4 to 1/2 every 3,000. Not nearly enough that I'm even remotely concerned about it.

 

I use 1- 1 1/2 quarts every 3000 miles depending on how hard I get on it. Been that way since the beginning. I use whatever name brand, non-synthetic, is on sale. Dealer said that's "normal". 36,000 miles and I just had the rearend rebuilt under warrantee (35998 miles).