I'll get my plugs checked out. My tires were a tad low, but I'm not sure if that is enough to change my MPG.

I'm also getting an oil change. Some other fluids are changed as well, but I don't know which ones those are.

 

marker227, I just bought the same truck you have 2 weeks ago. 05' with 21,000 miles. Anyway, My first tank, a combo of city and highway I got 17.5 mpg. I was very happy with that, coming from a durango that I only got maybe 15 or 16. Your mileage sounds pretty low if you were getting 11 or 12. How many miles on your ride? Check plugs, replace if needed, really cheap. Tire pressure is very important! I run 40 psi in front and 35 in the back. Make your calculations on mileage every time you fill up, gallons in, versus miles driven. Stock sized tires? Larger tires will affect mileage. Only mod i've done is a K&N drop in airl filter. Hope this helps some.

 

The tires are 18" I think. They are NOT stock... I don't have the model number, but say the stock tire model number is 50, these are 10 higher... so 60. I don't know the number, but I'll post it when I get the chance.

The truck is stock besides the tires.

The truck has 53k on it. I drove 100 miles exactly and filled up and after I did the math it was 11.9. My HUD even said 11 something.

I get the truck back from the shop tomorrow. I'll ask them in the morning to check the gap and spark plugs.

Like I said, a few times a friend or two mentioned my tires were a little low.

I'll be able to better estimate my MPG when I drive it for the week.

 

I manage around 19.8 mostly highway mileage. I spend very little time in and around Calgary.

 

My 2006 4.7 HO gets around 18 hwy and 13-14 in the city. That's with a pretty light foot.

I usually average around 16 or so (mixed driving) after a whole tank.

 

Has the speedometer been adjusted to accommodate the change in tire size?

 

About 18 on my v6 auto.

 

I don't believe so. I only know what I was told by my mechanic and what I see. Only tires were changed that I can tell.

Would a bed cover improve mpg?

I'll post my tire size and model number when I get my truck back... They are keeping it for one more day.

 

If your tire size was increased, your tires would turn less which makes your speedometer show you going slower than you actually are. This will give the appearance that you have poor gas mileage.

If you drive a few miles on the highway, you can probably watch your odometer change each mile a little sooner each mile marker.

Purchase the Superchips 3865, you can adjust for tire size as well as economy/performance. Search the forum and read about the tuner, there have been many posts already.

Bed cap may help a little. No drastic changes though.

 

I just got the truck back and I drove it a little.

All the plugs were looked at and are fine. Fluids were fine. Tires were added with more air. My mechanic said nothing needs to be changed.

I checked my trip-o-meter and it reads 177. I looked at my gas gauge and it's past the last line on the meter. So I have less than a quarter tank.

So, I drove 177 miles and I have less than a quarter of a tank? What gives? I'm only doing city and mild highway driving. I've been very foot conscious.