Mpg??????

[joediveguy]

Okay all you math wizzes, I just did a 136 mile round trip on a combination of highway (55mph) and back roads (45mph). I filled up before I left and when I got back, I used 9 gallons. That comes out to just over 15mpg and I am not happy with that at all. Then I started thinking about the speedo and if it was off, so I checked it with my gps and the speedo reads at just 10mph over what I am actually going. So at 55mph (spedo), I am actually going 45mph. How will that affect my above mpg numbers. I am running stock tires.

 

[porkysplace]

Was it 136 miles on the odometer of the truck or the gps ? if it was the odometer and your 10 miles per hour slower than it is reading you put about 23 miles more on the odometer than you drove or about 12.5 miles per gallon.

 

[joediveguy]

Was it 136 miles on the odometer of the truck or the gps ? if it was the odometer and your 10 miles per hour slower than it is reading you put about 23 miles more on the odometer than you drove or about 12.5 miles per gallon.

It was 136 according to the odometer. So then, I actually went 157 miles, divided by 9 gallons, equals 17.6 mpg. Better, but not the 20 mpg I was hoping for. Time to do some searching on how to improve on that…..Thanks

 

[combatmech]

Are you running stock tires? I had to recalc my MPG after I installed 33's on the truck. I'm getting about 16 or 17. I have no idea what it would have been with stock tires...at the time, I only drove the truck once or twice before I deployed....had the tires changed while overseas.....

 

[patracy]

Wait, you've got it backwards. If you were actually going 45mph and the speedo said you were going 55mph. If the odometer also was factoring high 18.19% like the speedo was, you actually only drove 111.26 miles, with 9 gallons, that's only 12.36mpg. Now typically larger tires cause the speedo to slow down, which reduce a uncorrected mileage calculation. But a faster speedo reading would come from a tire size smaller than factory.

 

[combatmech]

According to my GPS, at 55 mph on the speedo, gps shows about 60-62. I cruise around 65 (indicated) and GPS said about 70 +/- 2. I'm so confused....Maybe my speedo is way off to begin with.

 

[patracy]

No, in your case, that sounds right. With the larger tire size, the speedo/odo is running slower than it expects. Also note that as speed increases, the margin of error increases as well as the diameter of the tire.

 

[Darwin T]

from Highland Park IL to Iowa down to Louisiana and across to Texas i averaged about 12.5 MPG in my M1028a2/3. i also averaged about 53 MPH. my Speedometer is off and the faster i go the farther off it gets (5+ off around 30 and 12+ off around 53) 53 on GPS is 65 on the Speedometer. i need to get that fixed.

Edit - 4.56 gears (i think that right, but, i have no mechanical skill and don't really know what that means other than slow)

 

[olly hondro]

pump up the tires real hard. I run 45 psi, gets me 19 to 20 mpg.

 

[axlr8]

mad scientist....one great idea...we did that when running a 06 chevy truck loaded with a truck camper and 1000 lbs of gear, 1000lbs of flesh....averaged about 13 mpg first trip (out) pumped em up REAL HARD on the way back...(15.5) Mpg on the way back...it works!

 

[joediveguy]

Wait, you've got it backwards. If you were actually going 45mph and the speedo said you were going 55mph. If the odometer also was factoring high 18.19% like the speedo was, you actually only drove 111.26 miles, with 9 gallons, that's only 12.36mpg. Now typically larger tires cause the speedo to slow down, which reduce a uncorrected mileage calculation. But a faster speedo reading would come from a tire size smaller than factory.

****, that sucks! I am running stock 31X10.5's @40psi. What can i do to get better mpg? Is the IP adjustable? What can be tuned? It only has 32K on the od.

 

[Anubis8472]

I wouldn't go to overboard just yet.

Different fuel stations, even different pumps at same, can shut off at different levels. I've even had some that were nearly impossible to use, so when the pump says it's full is not a viable point to measure from.

You may be parked at a different 'level' when you filled up.
Fuel econemy is more accurate the larger your sample is.
Keep a log in the truck and re-calculate it after a month or two.

I know several times I've over-estimated how much fuel I need, only to be able to sqeeze an extra gallon, or even two, into that tank. Well beyond where I would normally have stopped and said, yep that's about as much as I'm going to get in there without making a mess.

To really get a accurate reading you could put a block of some sort down and drive the tank-side rear tire up on it, to lean the truck away from the filler.
Then fill the tank untill you can see the level at a clear spot in the filler tube.
Have an accurate reading of distance (if your speedo is off, so is your odo), and come back to the same pump and re-fill the same way.

Another thing to chew on is that you're probably running a 'winter blend' diesel fuel which doesn't provide the same MPG as a summer diesel.

 

[diesel583]

I would love to see 15, my M1031 gets 10 @ 55mph. It is loaded weighs about 9000#. If I drive about 45 it comes up to 13

 

[jdeoliveira74]

I average around 16 towing and 19-21 highway crusing at 68

 

[camp9]

I get about 15mpg with my M1009 with stock tires according to the odometer, but mine if off too. When going 65 off the speedo, my gps says 62mph.

How hard are you pumping your tires up to? I run 40psi in mine.

 

[unaffiliated]

I just filled up today and calculated 15.1 mpg's on my 1008 at max speed 60 mph city driving. I was hauling junk engines etc. to the scrap yard this week, four loads, about 50 mile round trip each load with about 800 pounds extra weight one way. My normal load is about 380 pounds over curb weight with necessary equipment in the bed (tools, chains etc.) and me in the cab. My speedo shows dead on at 45 and 55MPH according to the GPS. I guess I'm happy with 15 mpg, our 2002 Dodge Ram 2500 Cummins 4WD only gets 13-15 mpg empty.

 

[idM1028]

Let's see... Filled up on Wednesday and am down to about half a tank today. Driving to school mostly (26.8 miles, 53.6 miles round trip according to google maps) with a few side trips. If speed permits, I'll keep it around 60 on the speedo (I've got a M1028 BTW) I've noticed the speedo is usually 3-5MPH off the actual speed, so figure 55-57MPH. 3 trips=160.8 miles divided by 10 gallons comes out to 16.08MPG. Admittedly, I've had to do some driving that wasn't particularly conducive to fuel economy in this truck (Like yesterday when I was trying not to tailgate the Acura in front of me in a 55) I saw 70 on the speedo while passing... Once I passed I quickly slowed down before something went bang. I bet if I wasn't having to do stuff like that because of the stupid drivers around here, I could knock my MPG figure up a notch or two.