I drained out the differential when I first bought my truck and put in Super Tech 75w-90 Synthetic Blend to run it for about 10,000 miles to clean it out before I upgrade to the big boy stuff. The question has just hit me, what 75W-90 synthetic gear oil delivers the absolute best gas mileage on the highway? What are your thoughts? I'm thinking I can't go wrong with Amsoil Severe Gear 75W-90 (SVG). Any feedback is good. Thanks!
FYI - The vehicle is a 1990 F150 2WD 5.0L V8, 3.55 gears (non limited slip) and does just fine with 75w-90, so I won't be using 75w-140.
FYI - The vehicle is a 1990 F150 2WD 5.0L V8, 3.55 gears (non limited slip) and does just fine with 75w-90, so I won't be using 75w-140.