Just took my beast on the 1st highway trip up I-35 some 533 miles. The truck ran great, and got a fair and square 11.33 MPG at 1900 RPM (68 MPH). I am pretty happy with that number with the V-10, heck I see that some of you are getting 8-10 with a 5.9L. I am running a stock air filter, so will drop in a K&N and make sure my rubber is properly inflated. Those changes might even get me to 12 MPG!

 

put a cold air intake on, that may help a little, i know with my 14x3, i can get upwards of 17 on open highway, if i keep my speed down to like 65

 

yea i made a 700 sumthin' mile trip with my 5.9L and it was decent. I put 33/75/R16 BFGoodrichs All Terrains and ran at about 1600-1700 RPM at 70 MPH.

 

I drove up to Montana from Texas (2000 miles) and averaged 19MPG on my 5.2L at 65MPH. 75MPH went down to 16MPG. I'm running 265/75R16 BF Goodrich Land Terrain tires @ 45PSI.
That 19MPG impressed the crap out of me. I normally average 11MPG city. And that's with an all stock engine and bad plenum...

 

At the risk of sounding like a dick, which I'm not trying to be, may I ask how you calculated the 19 MPG?

 

Quoted for truth!

 

My gas gauge doesn't work, so I always filled my tank. I took the miles I drove, and divided it by the amount of gas I had to put in the tank to fill it (amount used since last fill up).

 

OK, so it sounds like you used the proper method. Any way we can see some of the actual numbers? Some of the actual miles, actual gallons put in?

Reason being, no offense intended, but we've had a fair number of guys over the years claim a MPG number by the proper method, but once they gave us actual numbers, it turns out they had exaggerated and were actually getting 2 MPG or so less than what they claimed. (One of those things where every time you tell the story, the fish you caught gets bigger and bigger...)

Have you ever corrected your speedo for those size of tires? What tires were on the truck from the factory (it will say in the door sill, IIRC)?

 

I'm not going to go with the CAI. Don't need more power and it would take forever for the CAI to pay for itself in MPG. I am actually happy with 11.33. Hell the truck is a V-10 with 4.10 gears, and 35X12.5X16.5's. I ain't driving no escort here folks. My stock as hell '03 Siverado 1500 (4.8L) gets about 17.5, so I think 11.33 is pretty good for the beast. Besides, I can't pull stumps and tear down buildings with the chevy!