Ok I have read and read and do not have a good idea on MPG

First off. I bought my first cummings Saturday in Texas, a used 2005 3500 with 165K miles on it. Well broken in!!!

I drove back home Sunday and Monday a total of 1300 miles.
On Sunday we got stopped and idled a lot because of wildfires in the panhandle. Driving was speed limit or less (under 70) idle time of about 1-1.5 hours while the roads were closed. The overhead showed 15.7. I filled up in Amarillo only 225 miles since I last filled up and hand calculated to 12.8 mph. The overhead is off by 3 mpg which surprised me. I expected it to be off but not that much.

Monday we finished the trip again driving speed limit, 70 when we could until we got to I-25 then 500 miles at 75 mph. I gassed up twice for a total of 47.7 gallons total miles 776 for 16.3. The overhead read 19.1. Again way off. I wish it were right.

Is this always off?
Are the numbers everyone is quoting for mpg's based on the overhead. I see some members are quoting hand calculated milage but what about the rest?

Based on what I read I would have expected closer to 18 or more on this trip, even at 75.

Any advice for a newbie. Should I expect better? What can I do beside go slower than the speed limit to help.

Is high teens, low 20's even realistic? If you are getting hand calculated 20+ what are you doing to get there?

I live in Wyoming and we have open roads everywhere there is no real city driving to be had where I am. Easy driving. I just would like to get a little better milage.

 

Ive been working in phx for 2 weeks , Round trip 234 miles have averaged 13.5 to 14.3 hand calculated. My over head reads 15.8 t0 19.1.

 

I'm on my 5th tank in my new truck and my 06 has never been more than 1.2mpg off. Also it is a "cummins".

 

Mine's off about the same 1+ mpg although my overhead usually says 1+ mpg lower than my hand calculations. Does this mean that the speedo is reading low,and my odometer should show more miles?
For me, at 75 highway i'm running about 2100 rpm (3.73's) and getting about 17-18 mpg
Cheers
Mike
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My truck likes running between 1600 and 1900 rpm for best mileage. That's 60-70 mpg roughly. I'll get about 20 if I can run it that way for a whole tank.
Mike
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Im a 2nd gen. guy, but my overhead is off by 6mpg, everytime, everytank. So it actually quite accurate -6mpg

 

My daily commute is only 11.2 miles each way and my 2006 CTD QC 2500 4X4 is getting 17mpg and the display only reads 14.9-15.1 I have 4000 miles on the truck so far, and got better than 20mpg on a tank of Nevada fuel on a return trip from Utah to CA at Christmas time (truck only had 1000 miles on it then).

 

I have a question,when you fill up do you fill right up to the neck of the tank and see fuel?I have found that the only way to get a true fuel mileage reading on these trucks is to fill right up to the neck.When the pumps shut off I can still get at least another 3-5 gal. in my tank.coobie

 

I'll bet you're not filling the tank the same each time!! The fuel tank vent mod will help in that regard!! My overhead usually reads about 1.5mpg low but as much as 2.5mpg low. It's reading 17.4mpg right now. I have 1/4 tank of fuel left and 458miles on the tank so far!!!

 

Mine is very accurate if I drive the same way for the whole tank (i.e. long hwy trip). However the accuracy waivers when I do mixed driving like trailer pulling, hwy driving, city....all in one tank. Its not ever too bad off...maybe 2 mpg at the most.

 

Thanks for all the info.

I always fill up the same way and include the neck. I spend long hours driving and I amuse myself by doing math as my wife says. Constantly recalculating the milage and my estimates for milage to empty. I don;t really need the overhead but if it is there I want it accurate and consistant. LOLOL. I know it sounds silly but that is what I do on trips when I am driving 600-800 miles at a time. If it was up to me I would never stop until the tank was empty to maximize the mileage but my wife has other ideas. ha ha ha

I hope it is just cold(colorado, wyoming), wind (texas panhandle) that caused it to be lower than expected. I did run at 1900-2000 rpm's most of the time and noticed towards the end that the truck was noticibly quiter at 1900 or under (around 68-70 mph).

I may look at a winter front as I have seen some encouraging posts about them and it get quite cold here over the winter and winter is long. I bed cover of some sort seems like it would help as well.

 

mcasey-I live in the cold climate and travel about 10 miles into town (rural) and my water temps just reach the normal operating temp in that distance (thankgoodness for heated seats) Stuffed in a sheet of hard board in front (actually fits well, painted black), decided to purchase a factory cover. Service M stated waste of money because the thermostat stays close untill it reaches the correct temp. The blanket is only required when engine temp begin to drop when traveling. In other words they never get to the required temps. Would the temp rise quicker with one, he didnt seem to agree. Anyways, retained the board up front instead.

 

In January I did 2500 miles round trip from WY to AZ and back, experiencing a wide variety of driving conditions. I hand calculated 20.4 mpg for the total trip, which compared to 19.8 on the overhead. The overhead is usually within .5 and typically registers lower than hand calculated, although occasionally it is a little high.

 

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