03 4.8 Fuel Mileage

[lil Scriv]

Have a Quick question for you Guys. I recently Bought a new to me truck, a 2003 Chevy 1500 ext Cab short bed 2wd with the 4.8 in it. has 160,000 Miles on it. The issue I'm having is Fuel Mileage, I'm getting about 12-13 in town and 15-16 on the highway, The thing that I know is hurting me is the 20" Wheels on it, They throw the Speedometer off about 5mph at 65 but I still think it's below average. it runs ok. some times it seems like there is a power loss and other times it has no issues at all. it has about 30-40k old Plugs and wires, New Cats (old ones started Rattling) Short tube Headers and Cherry Bomb Extreme Dual Exhaust, Cleaned the Throttle body and MAF and ran some Seafoam through it for the heck of it, about the only thing left that i know to do is put some o2 Sensors on it and clean the Injectors, no Engine light or anything along those lines. if there is anything I'm over looking let me know i'm just kinda at a loss and looking for Advice.

 

Thanks in advance.

 

-Robert

[Chris]

I get between 15-17 averaged out for the week. About half the tank is hwy. The hwy is stop and go sometimes because of a lot of end of fiscal year construction. I have 20s. Speedo is 1 MPH off. What gears do you have. I have 3.42's

 

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[KMGZ400]

i have a 2003 4.8 with 285's and 3.73's and i get about 13-15 city. maybe a little better on the highway so that might be about as good as your gonna get with that truck.

[05chevyon40s]

That doesn't sound right cause I have an 05 Chevy 1500 4x4 4.8L regular can short bed sitting on 40s with 4.88 gears and I get 14 to 15 mpg

[05chevyon40s]

Also do u have a base model truck or do u have a display of your average fuel mileage because if your speedo is off your not going to get an accurate distance or mileage trip so that u can compare the distance and amount of gallons ran through it your calculations will be off because it throws your odometer off so you really have more miles on your truck than you think

[05chevyon40s]

And make sure you clean or change your air filter, fuel filter check tire pressure, change oil regularly and use good recommended brands and run some kind of cleaner threw the engine and fuel system to clean it out incase an injector might be stopped up or it might not be sparking correctly and just dumping excess fuel into the cylinders I would check all those things before going to expensive repairs

[vernons9358]

my 2001 chevy silverado has 4.8 engine and i believe 3.42 gears,magnaflow single in dual outlet exhaust.. bought it 6.5yrs ago and have always averages 16/17 mpg... even on the highway stays right at 17. and i drive like a grandpa most of the time..