maybe2fast

Just from pouring the dino gear oil, I am wondering how much drag that thick oil presents on the rolling resistance. MPG battle has begun and wondering with an XJ that is 98% road driven and 70% of that is highway what could be gained my thinning out the diff fluids. I don't want to hurt the diffs either, but there are not lockers in mine and have no clutches and LSDs to damage.

Diesel

Gear fluid gets extremely hot and thins out. I would not put anything thinner in there.

99 Purple XJ

X2 its designed for that purpose

maybe2fast

It was also designed when gasoline was .99 a gallon, so I was wondering if there was room for improvement.

I don't want any "if you want mpg drive something else" it is a valid question and a possible improvement on old thick tar oil

Diesel

No, there is no improvement. It is that thick so it lubricates and cools correctly.

jebmccall

defnitly dont run anything but the recomended weights. needs the thickness to lubricate and keep the gears cool.

freegdr

a happy mechanic for what you pay him for rebuild would be only gain

djb383

Changing your handle to "SlowDown" might get u an extra 1-2 mpg.

Bbasso

slow down?
lower the jeep?
Hwy designated tires?
wax the jeep?
remove all excess weight?
If you want to get into increasing the MPG, try the things that might not hurt it.

maybe2fast

not trying to start a mpg debate, just bouncing an idea off of you guys. and the bounce was flat.

-maybe2slowdown

djb383

FWIW, there's nothing tougher on a lubricating oil than gears.....it's called "shear". The proper/recommended manufacturer spec/weight gear lubricant must be used. The correct lube spec/weight is a compromise between economy/protection.....engineers have stayed up late at night thinking about it/developing it.