Has anybody had a problem with your stock truck (no programming or anything) and the readings being off?

For example...my mpg on my '06 read about 12 mpg. On my '05 I always got around 16 - 17 mpg.

My truck also gave me the "low fuel" warning today so I stopped to refuel. According to the owners manual, you get the warning when you have approx. 50 miles left before you are empty. So I topped off the tank and it only took 23 gallons which means I had 7 gallons left in the tank (30 gallon tank). If you do the math I should have had at least 84 miles left before empty.

Has anybody had any problems like this? I purchased the truck last Friday and it came with the 20 rims and the Pirelli tires. Has anybody had this happen where the pcm isn't flashed for the proper tire size from the factory?

 

The low fuel warning is designed to register conservatively. Even though it says "50 Miles to Empty," in reality there's typically a 3-5 gallon (or more) buffer. This is because the fuel pump itself is cooled and lubricated by fuel, so there's a CYA zone built in to prevent prematurely running the truck completely out of fuel which may damage the fuel pump in the long run. I can drive my truck 'till the low fuel warning comes on, fill up, and with a 27 gallon tank I can only cram about 23-23.5 gallons in there.

As far as your low fuel mileage readings...how many miles do you have on your '06? I remember it took about 800-1000 miles and a few trips along my daily commute for the fuel mileage thingy to settle down. Mine typically hovers around 16-18 mpg - when I first got the truck, for the first couple tanks I remember it never reading above 15 mpg or so.

 

I am supposed to have the 30 gallon tank and most of my miles (90%) are freeway miles. So to get 12 mpg with primarily freeway driving is scary. It means I will probably average 8 - 9 mpg city driving. I have approx. 350 miles on the truck and I don't remember my '05 having this problem. But then again, it was an XLT and I didn't put the lariat cluster in it for a month or two after I bought it so I don't have an accurate tool to measure against there. I was shocked to see I was only going to get about 320 miles out of my 30 gallon tank of gas. I used to get 420 - 450 out of my XLT. Both have the 5.4L and are SCREW's. The biggest difference between the two are the tires (17" rims vs. the 20" rims).

I guess I will pull out my gps tomorrow to test the speedometer, that will help determine if things aren't set correctly.