Well, I run a Mag Hy-tec and Redline and pulling the Grapevine, ambient aroun 85, pulling a GCW around 18K with 3. 54 gears and running at 65mph I peaked at 195, so I'd say your not doing too bad, but lower is better. I think you'll be very pleased with the cover and oil. I have a temp sender mounted in my cover. Nice thing to have. Things to consider are speed, grade, weight, gears, and ambient temp. If you have 4. 10 gears doing 50mph over the hill on a 5% grade I'd say you're on the high side, but with 3. 54, you may be about right for stock oil and cover. The first mod to my truck when I bought it was the Mag Hy-tec.