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Re: 14.7
75W90 Mobil 1 synthetic Gear Oil in both differentials. Yes, the front one, too.
GM AutoTrak II in the NPG transfer case (the new variety "II" is also synthetic).
Do some tribology research, learn about polymers as VI enhancers, and you'll break your habit of Quaker State/Pennzoil for good. Try a more highly refined base stock oil like Valvoline or Shell. Or better yet, check into PAO synthetics instead.
Checked the alignment lately? Excessive toe can kill mileage.
Is the odometer correct? Oversized tires or a poorly calibrated speedometer can give the impression of poorer than actual mileage.
Is the EVAP system intact? And EVAP system that doesn't seal and recover vapors can lose 7% of its liquid fuel volume in a week in warmer temperatures.
Even though the cats are new, is the rest of the exhaust system intact?
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