Mine is a 5.4 with 3.55 gears. Not sure if it is totally believable but I logged over 19 on several occasions doing 68 or so on the interstate with cruise. Before installing the bedcover it never topped 18 mpg. Will be interested to see if the improved mileage continues.

 

My first tank of gas got me about 9mpg, that was all in 4x4 and of course playing around with a big engine(old truck had a dying 4.3 V6) 2nd tank with all city, 90% 2 wheel drive and only one time of snow donuts was just over 12mpg. In both cases I'm getting 4-5mpg more then my old 1991 s10.

 

Why shouldn't it be believable? If the gas pump is correct (and there's no reason to think it isn't given the way those are regulated) and your odometer is accurate, it's just simple math. No belief required.

I really think the bed cover makes a difference. Without it, you're basically dragging a huge board (the tailgate) through the air. That can't be good.

What are your highway rpms? I'm ticking over at 1500 at 60 mph indicated, which is more like 63-64 mph on account of the larger tire size throwing off the speedo.

 

Have no problem doing the math. The general consensus seems to be there is not consensus about whether or not bed covers actually help mileage, especially by up to 10%.

Not exactly sure on the rpms's Probably around 1800-2000 at 70 mph.

 

You would think, - but Myth busters proved that it didn't make a difference with or without a cover.

 

Also, if your getting 18-19 mpg with a 10th generation 5four, you should be on that Ripply's believe it or not television show. That's a record for sure.

Perhaps there's one of those top secrete Tornada's wedgied into the intake pipe ehh ? Has to be something as spectacular as that I expect.

 

Getting better mpg than what was shown on the window sticker 10+ years later is quite an achievement. Especially with a stock truck.

 

Not entirely sure what my diff ratio is, never felt the need to look. But I have the 4.6l v8... FX4.

 

I would bet my paycheck that all of these people who brag about spectacular mileage, or who complain about absolutely terrible mileage... they all have the speedometer and odometer completely out of calibration.

The speedometer/odometer is about +/- 5% from the factory. Add in some non-stock-diameter tires, unknown rear gears, etc.... and your mileage calculations will be all over the place.

GPS mileage averaged over several (ten?) tanks will get you a really solid idea of your mileage. One tank is not enough.
Or you can do what I did: use a GPS and a programmer to calibrate your speedo.

Fun fact, a buddy of mine has an old k-10 blazer - it has an aftermarket GPS speedo/odo. It is always correct regardless of tire size because it is not connected to the driveline.

 

How much do you make again? I'll PM you my paypal address so you can send it over.

I said I get 9-10 which I would consider terrible. My gears are stock and I know the ratio, my tire size is stock. I've tested with Magellen GPS, phone GPS, I have had 2 programmers and have ran my truck stock. I've adjusted for squatting height of the tires. I'm within 2 mph at 60 on the extremes of the combinations. Over 10 tanks at the max of 2mph, there would not be a significant enough difference to bring me up much higher in average mpg.

Now what should I buy the money you're going to send me?