7 MPG big issue what am I doing wrong?

[olyelr]

I have driven the route from Kansas City to the Front Range of Colorado during the winter while towing my 15 Travel Trailer on I-70 several times with my PW. Even though it's around 600 miles, the majority of this route is up hill. Roughly 99%. It averages out to just 8 feet per mile, but then it's an approximately 1 mile of elevation gain. Every time that you're going down a slight hill, you've got to go up an even bigger hill more often.

The speed limit is 75 MPH. So being just barren grass with no trees you do 80 MPH plus to keep your sanity. Afterall, the other traffic does. With the usual eastern hard blowing wind at a steady 35 MPH, this headwind sucks the gas down to 5.7 MPG and lower when you're floored trying to maintain the speed while towing. Even empty it isn't easy on the gas consumption. The barbed wire fences don't slow the wind down, neither do the 400 foot high wind farms which aren't out there due to any lack of wind to turn those huge blades.

Add to that during the winter some 20 degree Fahrenheit temperatures and below these cold conditions suck the gas even more due to the denser air. Engage the 4 wheel drive to drive through the unplowed snow and even unloaded I have seen under 10 MPG with my 34" 285 75R17 tires while empty.

There's no need to purchase the higher than 87 octane gasoline out here due to that's the mid-grade and there's less atmospheric pressure higher up to ping on it. Also, our winter blend fuel and high elevation just cuts the power in the Power Wagon. Floor it to get to Colorado and then floor it up our mountains to make it over the 11,000 foot passes to find even more mountainous terrain to suck down the gas.

You're MPG is good.

I wouldn't say good... but it is close to normal LOL.

Now, my wifes yukon xl denali that feels like it has twice the horsepower and gets 18-20mpg... now thats good!

 

[MJockey]

I have driven the route from Kansas City to the Front Range of Colorado during the winter while towing my 15 Travel Trailer on I-70 several times with my PW. Even though it's around 600 miles, the majority of this route is up hill. Roughly 99%. It averages out to just 8 feet per mile, but then it's an approximately 1 mile of elevation gain. Every time that you're going down a slight hill, you've got to go up an even bigger hill more often.

The speed limit is 75 MPH. So being just barren grass with no trees you do 80 MPH plus to keep your sanity. Afterall, the other traffic does. With the usual eastern hard blowing wind at a steady 35 MPH, this headwind sucks the gas down to 5.7 MPG and lower when you're floored trying to maintain the speed while towing. Even empty it isn't easy on the gas consumption. The barbed wire fences don't slow the wind down, neither do the 400 foot high wind farms which aren't out there due to any lack of wind to turn those huge blades.

Add to that during the winter some 20 degree Fahrenheit temperatures and below these cold conditions suck the gas even more due to the denser air. Engage the 4 wheel drive to drive through the unplowed snow and even unloaded I have seen under 10 MPG with my 34" 285 75R17 tires while empty.

There's no need to purchase the higher than 87 octane gasoline out here due to that's the mid-grade and there's less atmospheric pressure higher up to ping on it. Also, our winter blend fuel and high elevation just cuts the power in the Power Wagon. Floor it to get to Colorado and then floor it up our mountains to make it over the 11,000 foot passes to find even more mountainous terrain to suck down the gas.

You're MPG is good.

Man that thin air must really kill your power. Even towing 8000 lbs, I have never needed to floor it to maintain highway speeds. And no it not flat in East Tennessee. I also get 9-10 mpg towing that weight (with summer fuel and OEM tires).

 

[Grand Mesa]

Man that thin air must really kill your power. Even towing 8000 lbs, I have never needed to floor it to maintain highway speeds. And no it not flat in East Tennessee. I also get 9-10 mpg towing that weight (with summer fuel and OEM tires).

At the slower speed limits of towing at 70 MPH my MPG has improved by approximately 1/2 MPG with utizilizing 1" taller tires than the stock. Not so with the higher speed limits highway MPG. The 75 MPH and 80 MPH speed limits near here take a lot more gas whether I am towing or not.

 

[firefly1178]

Down load a speed/GPS app on your phone and run it. It will give you your actual speed. Then you can do the math and figure out what % your off at any speed if. If your off 10 mph at 50(GPS says 60) your off by 20%. At 30 mph you would be doing 35, which would mean your would be off by 20%

 

[firefly1178]

Your mpg would also be off 20%.

 

[olyelr]

Down load a speed/GPS app on your phone and run it. It will give you your actual speed. Then you can do the math and figure out what % your off at any speed if. If your off 10 mph at 50(GPS says 60) your off by 20%. At 30 mph you would be doing 35, which would mean your would be off by 20%

That will indeed work if you just want to know your speed. However, I highly recommend actually changing the computer to a correct speed, otherwise the shift points will be way off... and its annoying as hell. Been there done that.

 

[Trailmaker]

...but will help in resale
If you drove 100k but your OD says 80k.
Makes me think back on the vehicles in my past that had the wrong tire size on it...I have been duped!

 

[firefly1178]

Yes but you will know your actual speed and mpg. Back in the old days that was the only way. But you had to do it by running the highway behind a friend doing 60 in a stock vehicle.

 

[Trailmaker]

Yes but you will know your actual speed and mpg. Back in the old days that was the only way. But you had to do it by running the highway behind a friend doing 60 in a stock vehicle.

Back in the day it was adjusting your speed to mile markers. Getting exactly 60sec between each mile marker put you at 60mph.

 

[Grand Mesa]

Generally GPS apps altitude fixes aren't as accurate as their horizontal fixes. They don't take in account for the distance traveled in elevation gains and descents nearly as precise on a gradient vs a level road. Need a flat stretch of highway in order to obtain a more accurate reading to both check and adjust your speedometer settings. I found out the hard way about this while trying to set my AEV Procal on a straight road with a 7% grade.

https://itstillworks.com/accurate-mph-speed-gps-2016.html

"GPS Speedometer
...They can also under-report speeds when the car is climbing or descending on a steep road, since GPS altitude position fixes are less accurate than their horizontal position fixes."

 

[blackbetty14]

Your wheels and tires aren’t helping and try to coast as much as you can. Other than that your gas is going to drop about 3mpg due to winter gas blends which have more 02 to help combat the cold so you get less MPG. When spring rolls around and temps go up and the gas stations use up the winter stuff you will also see a boost in MPG.

 

[JS4024]

Don’t by a 60k plus truck, add 15k worth of mods then whine about the MPG.... yup I am that a$$hole. To be honest it amazes me how people buy something that gets single digit mpg then want to ***** about it. Want good mpg drive a Prius. If you run non stock tires your EVIC and your odometer are not accurate at all. Best thing to do is fill the tank, use a GPS, get on the highway and drive 20 miles, turn around and come back, refil the tank. Divide the Miles by the Gallons used.

 

[62Blazer]

As stated above you need to verify that the speedo/odo were calibrated for the larger tires. If not, going from the stock 33's to the 37's means that you are actually traveling around 12% more miles than what is being shown on the odometer. That's the difference between 10 mpg and 11.2 mpg.

With that said, I would expect to see a noticable decrease in mpg going to 37" tires. You are dealing with the increased leverage of the larger tires plus they heavier. Combine those two factors during stop and go city driving and it will use more gas.

For the comment about regearing, just because the rpm's are now higher at the same speeds does not 100% mean the fuel use goes up. There are a lot more variables going on besides just engine rpm. The main factor is how hard the engine is working and how much fuel the engine is using. The best example is you can be sitting in the driveway in neutral and it hardly takes any throttle to rev the engine to 5,000 rpm. On the other hand if you are pulling a steep grade while towing a heavy trailer you can have your foot to the floor at only 3,500 rpm........guess which condition is using way more gas? Lower gearing can have a similar affect as the engine may not have to work as hard. In general, the overall gearing needs to match the tire size and there is a decent chance you can improve mpg by going to lower gearing when you increase tire size.

 

[Marshall]

I don't understand 9 m/g, but I don't have a PW, how much difference should that make ?
my mileage is about double that in town, and I am running the standard 20 " tires. 14 sport loaded

 

[olyelr]

I don't understand 9 m/g, but I don't have a PW, how much difference should that make ?
my mileage is about double that in town, and I am running the standard 20 " tires. 14 sport loaded

thats just it. I have a ‘17 half ton and a ‘16 power wagon. The half ton gets 18-20mpg, the power wagon gets 12 unloaded. Its just the way it is.

 

[jimboschnitz]

The only thing I can say is with all the mods and your intention of going to 4.88 gears, fuel mileage shouldn't be a factor. It's a great looking truck, but with the lift, tires, gears etc., you aren't going to get fuel economy.

 

[62Blazer]

thats just it. I have a ‘17 half ton and a ‘16 power wagon. The half ton gets 18-20mpg, the power wagon gets 12 unloaded. Its just the way it is.

The half ton weighs around 5,000 to 5,600 lbs. where as the Power Wagon weighs over 7,000 lbs., and a lot of that additional weight is rotational mass in the form of larger transmission, transfer case, driveshafts, axles, etc, etc.... Rotational mass has more of an affect than static mass, meaning that adding 50 lbs. to the weight of the wheels that you have to spin plays a much bigger role than just adding a 50 lbs. sack of cement into the bed. The Power Wagon also has more aerodynamic drag as is sits a good bit higher than the 1500. Basically, if you took a 1500 and put a lift kit with larger and heavier tires and then threw 1,500 lbs. in the bed I bet the fuel economy would get pretty close to the Power Wagon.

 

[MarineBSP]

I have followed this and other mileage threads over the past year, and an added cause of lost mileage sometimes ignored is the change in ride height that comes with a lift, level, and/or larger diameter tires. The bottoms of our truck are a wonder of wind catching mechanical complexity. I've wondered about the stock nose-down attitude designed into our trucks and how much it contributes to mpg - and my switch to 65 series LT tires seemed to change my truck's wind noise in calm air, with only a 1/2 inch increase in ride height.

When all is said and done, I have to agree that the main thing for me to remember is that my RAM is not a Prius, or even my wife's minivan. I bught it for the versatility and utility, not mileage records. For economy, I try to drive my 15-year-old sedan when I don't need a truck - but once in a while I give in and drive the truck just because it's fun.

 

[62Blazer]

I have followed this and other mileage threads over the past year, and an added cause of lost mileage sometimes ignored is the change in ride height that comes with a lift, level, and/or larger diameter tires. The bottoms of our truck are a wonder of wind catching mechanical complexity. I've wondered about the stock nose-down attitude designed into our trucks and how much it contributes to mpg - and my switch to 65 series LT tires seemed to change my truck's wind noise in calm air, with only a 1/2 inch increase in ride height.

When all is said and done, I have to agree that the main thing for me to remember is that my RAM is not a Prius, or even my wife's minivan. I bught it for the versatility and utility, not mileage records. For economy, I try to drive my 15-year-old sedan when I don't need a truck - but once in a while I give in and drive the truck just because it's fun.

Exactly why I drive a cheaper (and "Blah") passenger car to work everyday. Twice the fuel mileage and maintenance costs are 1/2 to 1/3 of the Power Wagon. I save $100/month just in gas and tires cost $400 every 60,000 miles vs. $1,000+ every 35,000 miles. However the biggest thing when it comes to money is the replacement cost of the vehicle as I can buy a decent used car for a fraction of the cost of a Power Wagon (or any 2500 series truck for that matter).

 

[dhay13]

When I adjusted my daughters Wrangler for 35's and 4.88's I just used my Garmin GPS to verify speed. I used the Superchips to set it but it was still off a couple MPH so ended up doing trial and error until it matched the GPS.