Last couple tanks, thought my fuel gauge was malfunctioning. Had 340 miles on a tank and had a quarter tank left. Did the math and found I want from solid 17 mpg to about a 20.3 average. No idea why, have'nt done anything to it lately. Seem to happen suddenly, same everything, even same crappy GetGo gas I get at Gianteagle for a discount. Not complaining mind you, just curious why after 8 and a half years and 115,000 miles on my 4.6, that kind of milage turns up. Never got it before, even when drove 100% highway.

 

In highschool guys would be talking about mileage so we would go out in the parking lot and add a couple gallons of gas and boy they thought they were getting the best mileage ever lol maybe someone is messing with your truck

 

you sure the pump filled the tank all the way? driving habits change any? maybe it just finally broke in maybe the fuel system cleared itself out. lord knows what happened, just keep up whatever it is that your currently doing and knock on wood

 

Summer vs winter gas mix can make a difference.

 

maybe your fan clutch went out and it just free spins. any noticeable power gain/loss?

 

The steadier she goes, the more the EGR re-flows- knauk knauk knauk

 

Summer blend of fuel kicking in

 

Your discount gas station has probably changed suppliers and yer not buying the same gas.

 

Yep, probably different fuel via new supplier or summer blend.

Could also have been very favorable weather conditions. Changes in barometric pressure, temp and humidity can influence how much power you make, so maybe you just needed less throttle to maintain your normal speed. Could have had a tail wind, too.

 

Switching from E10 to pure gas can give you that difference.

 

Could be a change in suppliers. I'll find out this week cuz I filled up at Marathon yesterday. only reason is I was filling the boat, and don't like to put the discount in it. Not that one gas is better than the other, but it makes me feel better.

 

Maybe the gas station has a correct fuel indicator. You see something in the news ocasionally about rigged pump indicators that read high.

Maybe the rings finished seating. Don't laugh. My 2000 5.4 used a qt of oil every 2500 miles until 80k miles and then would use less than a pint in 5k miles. Rings finished seating!

Maybe it's different gas with no alcohol.

Maybe it's about to blow up! I doubt this one.

 

I hope you're right. I'm just turning 80K. I have been getting 1.5 mpg better the last two tanks???