My trusty Chilton's manual says this:
Transmission = 2.75 pints
Transfer case = 1.7 pints
Front axle = 4.2 pints
Rear axle = 3.2 pints
Total = 11.85 pints or 6 quarts (~ 5.6 liters)
If the synthetic lube will really improve gas mileage, will it be enough to offset the extra cost? I doubt it. IMHO, a good quality 75W-90 will do.
Don, y'all
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