2006 gmc 1500 fuel mileage

[trkyman1]

I have a 2006 gmc 1500 4x4 with 5.3 engine and 3.42 gears. I was getting around 18 miles per gallon last august and now I am only getting 14-15 mile per gallon. The only thing different with the truck is I added a high rise bed cap, which looks very aerodynamic. My question is did anyone notice a reduction in fuel mileage after adding a high rise cap on there pickup?

[DalesCarpentry]

I am surprised you are getting 18mph with the 5.7. I have the same truck with the 4.3 Vortec and I get about 17 mph. I just added a high rise cap like you said and picked up another mile to a gallon. Dale

[DalesCarpentry]

Did you by chance change tires. I changed tires on my 2003 Silverado and lost 4 miles to a gallon. Dale

[dorothy daily]

04 1500 5.3 17.5 by computer. 05 avalanche same

[DalesCarpentry]

Have you looked at you air filter latley? Dale

[Siskiyou]

It depends on the trip with my 2005, 5.3 liter, 1500, 4x4 GMC.  I average between 16.8 and 17.0.  On a long freeway trip I will get 20.0 doing 65-70 mph on the flat in the valleys.  I notice a ½-gallon per mile when they switch to the winter gas formula. 

The cap on my rig is only cab high and I have a Yakama which I remove when not in use.  My earlier 1995 pickup drop from 19 miles per gallon to 14 miles per gallon with the addition of a full blown lumber rack.

[trkyman1]

Tires are the same but i will check the air filter. It seems strange this happend around the same time I installed the high rise cap and just before winter.

[Lloyd Smale]

check the air pressure in your tires. It can blead down after a while and give you worse milage. My 06 is a club cab 4x4 just like yours with the 5.3ho motor and 342 gears. When i first got it it would pull about 21 on the highway. I went to 285 tires and about the best it does now is 18. Now that is using the dash computer to figure it. My computer was ajusted by a programmer for the bigger tires but who knows how exact that is.

[Bigeasy]

If nothing else changed, but for the addition of the cap, then the cap would be a good guess as to the cause...

I have the same truck, 06 standard cab long bed with the 327 motor, auto tranny, and can baby 20mpg out of it on the highway.  17mpg or so is a more reasonable all around gas milage.  I mostly use this truck to carry several heavy bikes in the bed, without much effect on fuel milage.  Tow something though, and gas milage falls real quick like.

Larry

[bilmac]

I wonder about these built in gas mileage computers. I have a buddy that drives down the road in his monster truck and when he is cruseing down a hill with the wind at his back he will tell me to look at his mileage computer. Yup, that big ol truck gets 20 MPG.

[Lloyd Smale]

Larry your sure right there. My gas mileage falls off to between 10-12 just with a trailer pulling my utv. Those motors make good hp but its kind of up the rpm scale where they work best and there not the greatest at produceing torque. The old 5.7 liter motors were better towing motors. I was so discusted with the towing milage and power with mine that i was all set to step up to a desiel. Reality set in when i priced them. 45000 is about the starting price and mine is payed off and only has 23000 miles on it. Couldnt see making a payment again for something i use to tow maybe 5 times a year with. Ill live with the slug!

If nothing else changed, but for the addition of the cap, then the cap would be a good guess as to the cause...

I have the same truck, 06 standard cab long bed with the 327 motor, auto tranny, and can baby 20mpg out of it on the highway.  17mpg or so is a more reasonable all around gas milage.  I mostly use this truck to carry several heavy bikes in the bed, without much effect on fuel milage.  Tow something though, and gas milage falls real quick like.

Larry

[Preacherman]

Could be the new gas here in WV as of about 2 weeks ago all gas is 10% ethanol.Talked to a guy who has an 05 Dodge his mileage fell 3mpg on the new stuff.also the price increased 20 cents also.
Preacherman

[Siskiyou]

Milage in California took the same dump when ethanol was added, but they taxed it the same.  Selling more gallons means more tax to the State and Feds.