I have a 98 Ram Sport with a 5.2. It is a 2wd and at stock height. No matter what I do, it seems bent on getting 11.4 mpg, on the highway or in the city. I replaced the plenum gasket and the O2 sensor. I plugged the port to the A/C and cruise control to root out vacuum leaks. It has a new brake booster. It use to have all terrain tires on it and a poor alignment, now I have highway all seasons and a good alignment and that didn't help at all. I have a new ignition tune up on it. The fuel pump was replaced a few years ago. Before I did all of this it got 11.4, and now it still gets 11.4. It is getting on my nerves because it obviously has more power, so I drive it lighter, and its still has bad mileage. It does have a hot air intake on it put on by the previous owner, would this be the culprit? It also has no catalytic converters. This truck means quite a bit to me, so I plan on keeping it until it is ran into. It is entirely rust free. I also have a Edge Gas Evolution CS2 tuner.

The engine is not original to the truck and the intake manifold has that dividing wall in the middle of it. The engine had a severe amount of sludge that I cleaned out to the best of my ability. The pistons range from 150 psi to 165 psi in compression.

I may rebuild the engine sometime, so is there anything I can do then? i.e. different intake manifold or cam shaft

The big thing to me is that our 89 Chevy C1500 with a 350 gets 14 mpg around here in the same, if not worse, driving conditions. It does have a lot more power too. It has a Jasper engine in it from the 90s.

 

maybe a dumb question, but did you reset the trip computer display after doing all the upgrades?

 

You mean, reset it back to zero? I reset it every time I get gas, and I always fill it until it clicks. I religiously check mileage praying for an improvement. I have tried all the different kinds of gas too.

 

that's what i was talking about. those things might be accurate, but i don't trust them completely. i would punch some of your own numbers and see what it doing.

how many miles on it? have you serviced your fuel injectors or run some cleaner through the system?

 

so you're getting 11.4 from your own calculations? i read your post and assumed you meant the display kept reading that number.

the other possibility is that the truck runs better so you're stepping on the gas a little more. i happens

 

I have been using fuel injector cleaner for the past year. I kept the same size tire. I know the fuel injectors haven't been touched in 10 years.

 

How old are your O2 sensors?

 

Less than 4 months old.

 

What brand?

 

Bosch brand