i have a 98 k1500 suburban with a 10-bolt rear that needs to have the fluid changed. I can't seem to figure out if synthetic 75w90 (Lucas) is going to cause problems or not.

I have 305/60r18 (almost 33x12.5) and ride on the beach for most of my driving so it sees a good bit of load and will get hot in the summer.

Trying to figure out if it is better to run Dino 80w90 or syn 75w90...

Thx

 

I'd go with synthetic, 80-90 or 75-90