So all i ever heard is that my 99 1500 4x4 with a 5.9 should be getting around 18mpg. i have been getting a consistent 11 mpg. so before i get any smart *** answers Im not looking for 22mpg or i would have got a car, also i got the same not allowing my truck to go over 2200 rpm, driving the speed limit, and slowing down way before a stop so its not so erratic, still gets the same. i replaced my nasty air filter with a new one didn't make a difference. I checked the entire fuel system over and no leaks.
So before I replace the plugs, wires, and points (truck has 111000 miles and i doubt the original owner did any of that) or do anything else, what are stuff i should check??? thanks guys

 

18MPG out of a 5.9l gasser? Maybe, downhill with a 100MPH tail wind. Otherwise it's just not gonna happen.

111,000 miles and no maintenance? Do the 100k maintenance now, including oxygen sensors, PCV valve, the whole shebang. But not the ignition points -- there ain't any. That oughta get you 1-2MPG and perk the critter up a bit.

 

Is this town or highway driving? That will make a difference. If its everyday running into town just driving around the 11 is probably close to what you should expect. I have the 360 in mine to and DAMN it loves gas! HA

 

about 75% highway, i live in bum ****ed egypt lol and yea they must love gas, i have a 99 ranger with a 6in lift and 35 12.5's and still get 15 mpg.

i thought all distributors had ignition points??? i figure i would do a all out tune up just wasnt sure if there is problem areas on the trucks, im a dodge diesel guy myself but just had to sell my girl

 

I could have heard wrong but i have heard theses 360's are doing good to get 14-15 mpg on 100% highway driving.

 

so its just like a hemi with less get-up-n-go damn!!!

 

My current '99 is great shape, has 178k miles is half ton ext cab 4x4 with 5.2/3.55 gears, I'm getting 10.7-13.7 at best. It's by far the worst I've had, I'm assuming stuff like cat/02's/tune up, etc... I bought it as a beater but it turned out so nice I'm using it a lot more than expected so I'm gonna start hunting the gremlins. My previous '99 was a 3/4 ton with 5.9/3.55, also ext cab 4x4, it averaged about 13-14 like most Magnums do, but it would honestly get 20.2-20.5 at a steady 60 mph cruise, by far the best of any of the Magnum engines I've owned which include a 4x4 '94 Dakota with 5.2/3.92 gears, 2 Grand Cherokee Limiteds with 5.2's and 3.55's and a '99 Durango 4x4 with 31" off road package and 3.92's, every one of those got 13-15 all around. Magnums are good engines, adequate power, and mpg but nothing to write home about compared to the GM Vortec engines and LS engines. Thne 4.7's and Hemi's closed that gap though.

 

My '98 chevy (350) got 18 mpg easy, had more miles, and more power. Sad.

Has anyone ever tried changing gears (higher ratio) without having bigger tires?
Mine seems to be geared too tall for the engine, cruises where it doesn't like to make power. Not a good thing for mileage.

 

My dad had a 99 with the 360 in it and he'll pull 18 all day, except when he hooks up to pull it drops to about 8. On the other hand I have an 01 with a 360 and I pull around 9-11, but it doesn't drop at all when I'm pulling. Could it be that they are geared different? Both are stock trans and gear ratios.

 

do you have any way of finding out what gearing your dad had? Tire size?