Hi All

I have a 03 ram 2500 5.7 Hemi 4x4. Now I know that motor doesn't get very good fuel mileage but a few weeks ago I noticed that I went from 12 MPG down to 8, I haven't done anything to the truck and my driving style and driving routes have not changed, I drive all back roads and usually drive between 40-45 MPH. I have 116K miles on the truck and I'm guessing the spark plugs are original as I'm the second owner but would old plugs cause that drop in MPG? DOesn anyone know what would cause a drop that big? Thanks

 

Yes that is possible that bad spark plugs would cause some of that fuel economy loss...

What octane rating are you filling up with?

Any modifications? (intake, exhaust, etc.)

How much weight in the bed? (any snow/ice/etc.?)

Is your check engine light lit up? (if so, what are the DTCs?)

 

If you somehow put E85 in the tank the MPG would fall a lot.
I would not think spark plugs would could a sudden decrease. Is this based on the overhead or also hand calculated?

 

i hope you are not thinking that the computer will give a good MPG reading. i only trust my record book. over at least 4-6 fills. always fill at half tank, at the same pump.

 

I use www.Fuelly.com

Check out the link in my signature...

 

The computer is optimistic. They seem to always show better mileage than the actual.

 

I'm using 87 octane and I always have used that. No mods, nothing in the bed, no engine light, its just very weird because nothing has changed except the MPG's but that's using the overhead computer that's in the truck. I downloaded the fuelly site and will use that and see if maybe just the computer is messed up. I'm still filling up once a week so I think maybe just the computer is malfunctioning.

 

The overhead calculates based on miles driven, it doesn't take into account idling. So that might be the issue if you've been idling more often with the cold weather.

Also, 89 octane is recommended for the Hemi... Might want to try and run two tanks of 89 octane through there and see where you end up. If the fuel economy is still bad I'd change the spark plugs, and change the oil and see how it goes.

 

That would make perfect sense seeing how this has started ever since I had my remote starter installed, been doing alot of idling with the starter put in...I'll also start using the 89 octane since this is what is recommended and go from there. Thanks so much for your help. I also have another problem that has just started a couple of weeks ago but I'll start a new thread on that. Thanks again.

 

Yep, 0 mpg averaged in with 13 mpg certainly will have an effect. Definitely want to stop using the 87. The manual recommends 89 at least. Mine says 91 but there isn't any 'round here.