Supposed to get around 17 MPGs highway, but I got about 100miles out of half a tank on a straight stretch of road doing 55-59 with cruise control.
I've been suspecting this poor milage but this was a long enough stretch to prove it. I'm up to date on tune-up and oil change.

 

Are you going by the gauge or actual fuel used?

 

Yeah ^^ what he said you need to know fairly close (+/- 2L) what the fuel usage is, the gauge is just a guesstimate. 17mpg is gonna be a best case scenario mileage, expect from 12-15.

Scott

 

By my estimates I'm running 11mpg. 15 mpg would be excellent.

 

You need an actual figure, not estimate. The gauges in these trucks are never accurate.

 

The fuel gauge in any vehicle cannot be considered an accurate measure of fuel used but the ones in these trucks are notoriously bad so you need a measure of miles driven from the odometer and fuel used to refill the tank to get anything remotely close to a decent MPG estimate.

 

Last time I calculated my MPGs it was 11mpg. Not an estimate.

 

You said it was an estimate before. I would check the codes.