I have a 2003 dodge ram 2500 hemi. Only mods to it right now is a cold air intake, flowmaster mufflers, and took the cat out and replaced it with a y pipe and i have it open all the time so the mufflers dont really matter. I have been getting around 13.5 combined bust mostly city. lets say out of 100 miles only 20 are crusing on the highway. Ive calculated my gas mileage out 5 times over the past 1 1/2 months and it has gone like this: 13.5, 13.1, 12.6, 12.1, 11.5mpgs. There is only 2 causes i can think of. The average temperature around here in oklahoma has dropped around 30 degrees or i switched to synthetic oil around 1 month ago. BTW just hit 78k miles. So what do you guys think?

Thanks, Isaac

 

My 2004 is a 1500 so it weighs less and at 82K, the gas milage is still improving beleive it or not. That said, your mileage for local stop and go is very close to mine. Couple of items come to mind. Here on the east coast, the winter blend gasoline reduces mileage 2-4%(government publications). Additionally, the rich mode is longer as its taking time for the engine to reach proper operating temperature. The warm up is extended by your flow through exhaust. Tires lose approximately 1 psi for every 10 degree drop in temperature and to me, that is a big mileage hog. On the highway driving, I see a very little drop in mpgs. My suggestion is to fill your tires as high as you can tollerate the ride while not exceeding the maximum on the side wall. I am assuming your running load range D or E.

 

Winter blend fuel contains more ethanol, you get less power from ethanol enriched fuel uses more gas hence low mpg, try finding ethanol free fuel or try starinol I think that's the name it reduces ethanol in your fuel
Or you have mechanical problems forming also check for dragging brake caliper and free moving bearings.

 

I am very big on tire pressure. I check every week and i run my nitto dune grapplers at 70psi. So you are saying the engine runs richer while its cold? I allow it to run for a minute or two before taking off and the engine temp gauge will get to the middle after about 3 miles. And also about the front brakes rubbing; they are a little bit but i was still getting 13.5 unless the rubbing has gotten worse. I first noticed when i was painting my front calipers and i could even hardly turn the rotor. I am due for new pads so i thought i would look into some drilled and slotted rotors because i have heard dodge rotors will warp over time.

 

Those couple of minutes uses fuel and gets 0 mpg. When you do your brakes, make sure you lub the sliders with appropreate lub. I seen too many cases where the factory skimped on the lub and the pads did not move easily causing additional friction. As far as rotors, on the 1500 they are crap. Even if they do not warp during the life of the pads, taking off material when turning them may leave them too thin to resist future warpage. I would guess the 2500 would have a much beefer rotor?


Those tires have a high rolling resistance, that equals more gas to move them. Hey, you gots a big heavy truck and it takes a lot of fuel to get it moving.

 

yeah, but i have not changed my driving style at all. i always let it warm up a little and drive softly. i was getting 13.5 with those tires. i think the front rotors are alot bigger on a 2500. Another question i have is right now for wheels i have 20 inch xd badlands and they dont even clear the caliper by an inch. how were the stock rims 17 inches? unless these wheels are just extra thick

 

Colder Temps and Crappy Winter Gas. My Daily drive like clock work every november goes from 29mpg to 25-26mpg.

 

More oxygen requires more gas. It makes more power too.

 

There are a few factors that come into play here. Each one hurting your fuel economy a little and when added up, the result can be major. Most have already been touched on in this thread.

First of all, by early November we are all getting "winter blend" fuel. The winter mix has a higher Reid Vapor Pressure which results in slightly less energy per volume of gasoline. In other words, you have to burn a little more of it to get the same results as with "summer gas".

Temperatures are decreasing, lower temperature air is more dense and the more dense the air is, the more fuel must be mixed with it to yield the same air/fuel ratio.

A CAI lets in more air volume simply due to the increased surface area of a cone filter vs. a flat filter. More air = more fuel needed, more COLDER air means that much more.

Air pressure in tires decreases as air temperature decreases. Running on lower air pressure results in greater road surface resistance which yields lower fuel economy.

20" wheels are significantly heavier than 17" wheels requiring more energy to move them. Energy overhead is higher in colder weather than warmer due to all of the factors I've listed. If you need a certain amount of energy to move your truck in 80* temps, you will require more energy to move it in 40* temps...

 

In regards to Hammer with larger rims, if i recall 1 pound of rim weight is equals to 7lbs rotational mass. I've looked for aftermarket wheels vary from 25lbs to 37lbs do the math the difference is 12lbs times 7 that's 84lbs more weight, times 4 wheels. Big difference