Grit Dog

I've found my lie o meter to be about 1mpg high with stock tires. With new 285-70's, no speedo change, hand calc including the difference in tire diameter, it's about right on now.
Winter highway driving 75mph +, mixed with a little in town driving = 16-17mpg. Summer time, same driving = 17-18mpg. I can get up to 20mpg if I keep it below 65, hahaha fuel isn't that expensive!
Just this weekend, I pulled 11mpg towing a 5500lb boat with a tower, 75-80mph into a pretty nasty head/crosswind. Got a little over 12mpg on the return trip, same speeds, less wind.

.boB

exwrestler, the answer to your problem is in your profile - 20" wheels. What do you think the weight differance is between those and stock 16-17" wheels? Both are forged alum. For that extra 3-4" in diameter, which do you think weighs more, forged alum? or air and rubber?

It's takes a lot of energy to get those big heavy wheels moving and keep them moving.

Those Nitto Terra tires are not helping you, either. They're wide, and have an off road tread. That increases friction and rolling resistance. The big tread also makes them heavy.

I don't have any numbers to back it up, but I would bet that there's a considerable weight penalty for that set up. If possible, put the stock wheels and tires back on adn see what happens.

thenrie

GritDog: Just to ask, if you have made no speedo correction and are running larger tires, are you using GPS to get your miles traveled for your hand calcs? You indicated you corrected for tire size on your hand calcs. How do you make that correction? I just correct my speedo/odo with my BD Outlook...because it's easy.

Regardless of whether your hand calcs compare favorably with your overhead meter, if you use your uncorrected odometer for miles traveled, your hand calcs will be lower than actual, because your odo will show fewer miles traveled than actual. If you have not corrected your speedo/odo I recommend using GPS for your miles traveled. You might be pleasantly surprised! You can also calibrate your speedo/odo correction using the GPS. Just keep adjusting until they match up with GPS (its just a push of a button with the BD Outlook monitor).

BLACKBEAR

Well boys there is different in fuel at the pump some gets better mileage and some gets less.So it is hard to check your mileage ever tanker the fuel is different.If the driver put in the additives that the company gave him this is how they tell you it is Shell or Texaco.

062500

My 06 gets between 11 and 13.5 around town at best and 15.5 on the highway. My friends 03 or 04 gets 4 MPG better than mine across the board. I have been dealing with dodge for 4 years trying to find out why my 06 gets such bad mileage. I have spoken to other 06 owners who claim they are getting great mileage (17 + mpg)

ranchertx

My 98 12 valve got 18 MPG on the hwy running empty.
My 01 gets 18 MPG on the hwy running empty.
My 07 gets 15 MPG on the hwy running empty.

People that claim they get 20+ are either using the overhead, or they are driving downhill with a tailwind.

modiesel

Since I put on Nitto 285's (almost 34" tall) I have lost a little milage. Before Nitto's, hand calced 17.3mpg, now about 15.7mpg. I sure love the look of the taller tire though.

steelblitzkrieg

People need to realize that 20mpg is doable, but it is rare. With mixed driving I averaged 17.5 with stock tires, now with same size MT's I average about 16.0. I have been +20 a few times over 3/4 to a full tank, but conditions played a big factor.

I also belong to a Jeep Patriot forum (27mpg highway rated) and many have the same complaints about people claiming 30mpg+. 28-29 is a piece of cake for me, 30-31 happens occasionally, and I've had 32mpg once or twice.

HVYHLR6North

Horsepower=fuel. All the mods like air filters, exhausts etc. all claim to boost hp., and save mpg's. Once there is a hp increase, guess what your mileage drops. I installed an airaid cold air intake with tube and a mbrp 4" turbo back exh. the whole time thinking to save mpg, well I lost probably 3-4. While towing 10 k fifth wheel I get 14 hand calculated. on the o.h. it read about 13.8. Previously I would get about 18 mpg towing over 20 empty.

The biggest thing is if guys are worried about fuel economy look at buying a jetta

rip 112

Most ppl lose mileage cause once they add a mod thats supposed to help mileage they cant help but romp on it all the time still thinkin they will get mileage. Its all in how you control your right foot, push it too hard don't expect great mileage.

rufushusky

Now I believe intake and exhaust on their own do little to nothing to help mpg or hp...so how do you loss hp without adding anymore fuel?

Mark03Ram

I see a few things here. NO one takes into consideration where you live. I usually get 15-16 around town driving in Louisville Ky. When I went on vacation to FL I got around 18 in town. Closer to sea level, different fuel blends, flatter roads... I have gotten over 22 doing 65 on the highway down there, but I get closer to 19 up here on the highway. Hills will always kill your fuel economy, higher altitude and different grades of fuel will make changes.

Another thing I see is ppl say they drive the same after power increase/mods. If you drive the same you will lose fuel economy, you have to accelerate the same, not drive the same. Think about this, lets say bone stock you leave a red light with 20% throttle, we know that in stock form there is not much fuel being feed to the engine at 20% throttle so you accelerate slower. Now you add a tune to the truck and it adds a good deal more fuel at 20% for better throttle response. Now the same 20% throttle is accelerating the truck faster, but you are driving the same cause you push on the throttle the same as before.

If you put the tune back to stock, drive a normal road and leave a light the way you normally drive, and count how many seconds it takes to get to the speed limit. Now go back and do it with your tune, I bet you get to the speed limit faster.

Bigger tires will take more power to get rolling and up to speed so that factors in. Rotating mass has a exponential impact on power needed, much like wind resistance. When I put the tune in my truck I had to make a conscious effort to accelerate slower and use less pedal to keep the fuel economy up. Was very easy to roll into the throttle and leave everyone else behind you. Now I try to be the slowest guy in the pack, and use my brakes very little.

I had a 05 Hayabusa sport bike. When I used to ride it really hard I would get about 2200 miles out of a rear tire, 3200 miles out of a front tire, and 6k miles out of brakes, I would also get 25-28 mpg. I now have a B king, same engine, same weight, just more sit up touring style bike. I dont ride it that hard and I am getting about 4k miles out of a back tire, 6k out of the front tire, and I bet I get 20-25k miles out of the brakes. I average 38-42 mpg. I could increase all those by riding it even easier, but it is a 170hp sport touring bike so you still have to have some fun lol.

The point is, if others around you get more miles out of tires, brakes, and better mpg, that means your driving style is more agressive, so you have to make changes.

FMB

Not to be argumentative, but my experiences differ (of course).I always (yes, always) get better highway mileage driving from Sac to Reno and back than I do driving the valley. Just a guess here, but going uphill, the worst mileage I've gotten was 8, pulling the Fox. Downhill (remember, round trip here), I get 99. Work that into the average.

You are not driving the same, as you say the stock truck accelerates slower and the tuned truck faster. The faster acceleration puts you at your 'cruise' speed quicker, thus acceleration, cruise and trip times are less over the same distance.

Mark03Ram

Well my experiance with hills is I always get worse fuel mpg, I live in alot of hills... even costing down hills, I guess it depends on if there winding road where you only do 40-45 mph and ride the brakes alot of if its costing at 60-70mph, but my uphill is slow and down hill is slow.


What I mean by you are driving the same is you have not changed how you drive, the truck is doing something different I.E why I said you have to accelerate the same.

So yes you as the person are driving the same way, you push on the throttle the same way, the truck is useing more fuel because its putting down more power, so you accelerate faster. This is why you have to change how you drive.....

steelblitzkrieg

Just an update:

My previous post was prior to lift and 35's.

I just went to Yosemite last weekend from the SF bay area using Hwy 4, Byron Hwy, 205, 120.

Sea-level to 6k to 4k to 6k to sea-level with plenty of 70+mph stretches.

My Lie-o-meter read 23.8mpg after the trip, hand-calc was 17.3mpg.