[v8Toilet]

My secret is I have 2WD, weigh in under 4400 lbs, have a tonneau cover, use all synthetic fluids (engine, trans, diff), and I have some breathing modifications. I also had a new Toyota air filter in at the time of the test.

My mileage was achieved traveling at 65 mph with the cruise control on and I was about 200 ft above sea level. 22.7 mpg was the best I have ever got with a few 21 mpg in there too.

If I go 70 + mph I’ll only get 18.5-19 mpg.

If you have 4WD you’ll take a highway mileage hit because 4WD trucks are higher off the ground, weigh more, and have more mechanical parts to move with more inertia even if your 4WD is not engaged. If you have a cap or no tonneau or bed cover you’ll have more aerodynamic drag. If you drive with your tailgate down you’ll have more aerodynamic drag. If your tires have high rolling resistance you could get up to 2-3 mpg worse gas mileage according to Consumer Reports. I bought tires with very low rolling resistance. If you have low tire air pressure you’ll get worse gas mileage. If you have a dirty air filter you’ll get worse gas mileage. If you have a K&N or TRD air filter you’ll get slightly worse gas mileage. If your 02 sensors are getting sluggish you’ll get worse gas mileage. If your engine tends to ping on 87 octane and the knock sensor retards the timing as a result of that you’ll get worse gas mileage. If you have bigger tires or a lift kit you’ll get worse gas mileage. If it’s cold outside you’ll get worse gas mileage because your truck will take longer to warm up. If you use the A/C or drive with your windows down you’ll get worse gas mileage. If you drive with all your lights on you’ll get slightly worse gas mileage (the fog lights each are 110 watts!) If the wind is blowing against your truck while traveling you’ll get worse gas mileage. If it’s raining out you’ll get worse gas mileage. If you have dragging brakes you’ll get worse gas mileage.

I think that’s it!