Anyone ever use 75-90w gear oil in their jeep with QDii? I know it doesn't meet specs and is too thin... But I have a work truck that has a 33,000 lb weight rating and it takes 75-90w... I wonder if the 140 is actually needed and if the 90 would get better gas mileage? Sorry, but I'm not going to be the first one to do it, just curious if anyone has done it and seen positive or negative results.