Actual Fuel Mileage

[scottyb]

After 2500 mi and a recently installed Titan 67 gal fuel tank, I have determined once again, that my truck's computer can not be relied upon for accurate fuel mileage. This is par with my experience on every vehicle I have owned since they started using trip computers. I'm hoping that the mileage will improve after more miles, but I don't expect the trip computer to be any more/less accurate. My results were the same before the Titan as after. Here are my latest findings;

Mileage driven 608 (Estimated 40% hills, 25% flat, 25% city, 10% off road)
Computed gallons used 43.7; Actual gallons used 47.3; error 8.2%
Computed MPG 13.9; Actual MPG 12.85

At a needle's width below 1/4 tank, my Titan fuel tank still had approx 20 gallons left, assuming it holds 67 gallons. Since the installer pumped the remainder of my OEM tank into it, I only managed to add 51 gallon at 1st fill up. That seemed about right by my estimate.

 

[Lynn1130]

I don't know about a Ford but I had to have my ECM reprogrammed for the larger tank in order to get the gauge and DIC to give me a reading anywhere near accurate. I am now within a couple of gallons on the tank reading and pretty close on the MPG.

I think there is a thread on here somewhere about Fords and reprogramming for larger tanks.

 

[brianharrison]

I assume you still have the DPF regen system working on your new truck - I could never figure out if the fuel/mileage calculator on my 08 Ford took into consideration the fuel dump into cylinder 7/8 exhaust during regen.

Since I cut off the DPF, the actual and ECM calculated MPG seems more aligned. I dunno.....

I added the Titan tank and did not reprogram the ECM for DTE - I watch the fuel gauge and trend the mileage per tank. Others have reprogrammed.

Brian

 

[pegmikef]

I had the firmware updated after I had my fifty gallon tank installed and I still have a slight delta in the mpg computation. I don't have the fancy computer that gives me the number of gallons . . . all I get is the MPG and MTE. I have always figured that the MPG is dynamic and only addresses the point in time that it is displayed, whereas a manual calculation is fixed and addresses the total amount of fuel consumed and total miles driven. E.g., my displayed MPG is 13.5 for the last 100 miles of a four hundred mile trip and that is the value displayed when I stop to fill up. Then I manually calculate the MPG using the constants total miles driven and total fuel consumed and I find that my overall MPG was 12.2. Anyway, I have found that I can pretty reliably count on 11 to 14 MPG dependent on the wind and terrain (my NT is only around 8500 pounds loaded).

 

[rgwilliams69]

I have the Titan 65 (67?) also and have had the computer updated for the new capacity. I get a pretty good variance on the gallons used on the computer to the actual gallons put back in, sometimes nearly right on and sometimes significantly different. Not good enough at catching the regens to know if they are the culprit or not, and I have to wonder sometimes if the gas station calibration is off in their favor. I have NEVER put less in that the computer registers, it is always near the same or more. For this reason the trip MPG can be off by as much as 1.5 MPG over a long haul. Here are some actual numbers from the last several fill-ups:

42.4 computer versus 42.7 actual
31.3 computer versus 32.5 actual
22 computer versus 24 actual
24 computer versus 24.7 actual
27.4 computer versus 29 actual

When it is really off I check the calibration stamp on the pump, of course they are always in compliance...

This always causes the lie-o-meter to show better MPG than I am actually getting. Not sure where that extra fuel goes. And you can see also that it is not static and not a variance that increases with the amount of fuel added, i.e error is not cumulatively larger with a larger fill-up.

ScottyB I'm assuming your numbers are NOT towing, correct? Because my new MPG is lower than what I wanted pulling the new monster 4100 I try to just ignore the whole thing and watch the temp gauges instead.

 

[ncc1701e]

After putting the 50 gallon Titan tank in my F250 the Ford Dealer who installed the tank reprogrammed the computer. I tend to look at the computer every time I fill up to see what the computer says the fuel consumption was and try to use this as a guage on how much fuel additive to include. The gallons pumped versus the gallons used have always been within 1 or 2 gallons.

As for MPG, I track every gallon of fuel the truck burns manually on a spreadsheet and the computer here again is pretty darn close. The Ford tech must have done a pretty good job.

 

[porthole]

The Ford tech must have done a pretty good job.

The tech only gets to download a profile, no input on his part.

Scotty - since your detailing your numbers you need to start with the correct tank size - 65 gallons it should be.
your +8% variance is just about exactly what the manufacturers allow for error+ - 10 %.

On all of my vehicles since they had calculators I have found them all to be fairly accurate. Maybe off a couple of tenths to a gallon here and there, but that could be as much as the user adding fuel variance.

Diesel foams up as it pumps. I don't really have an issue with the Ford Titan, but when I had the 52 gallon in my GMC, if I filled it at full speed it would shut off almost 10 gallons early. I tend to stop the full speed fill when I think I have 10-12 gallons to go and then set it for the slow speed.

My truck has always taken about what the gallons used reading shows, +- about a half gallon.

I just did 1000 miles up to Sault Ste Marie Michigan. Probably averaged 70 mph most of the way. Got 14.5
Same 1000 miles back pulling a boat. Averaging 60 most of the way, 50-53 in the 55 zones.
Got about 10.2. After a couple hundred miles I shoveled all the hard packed snow out of the boat. Mileage jumped to 10.6.
Before the last 500 miles I bumped the air pressure up from 60-65 and mileage went up to 11

 

[scottyb]

Greg, I wish those numbers were towing, but that's just every day driving for me. I suspect the Hill Country where I live is one of the culprits as to why I never get the reported MPG's. I know a lot of idling with the AC running in the warm months takes it's toll. Watching the computer, it seems like the average really drops while driving off roads as well. I did have the ECM re-programmed but assumed that only affected the MTE calculation. My previous Duramax was consistently under on fuel used and over on MPG. It varied from 1 - 3 gal off.

I will be towing the rig for the 1st time around town for some maintenence items before we head out to Big Bend in a couple weeks. I an very anxious to hook onto it. I never knew the 10% allowance. I suppose my vehicles have always been within that, but always less gallons than actual and higher MPG than actual. I alwat try to fill the truck the same each time. Sometimes, if the driveway is sloping, the fill level can varry significantly from the high side to the low side. However, if you take a long range sample, say 5K - 10K, all of these things tend to average out.

 

[Netem]

Looks like you ran the wheels off that boat trailer. :>)

 

[TXBobcat]

Wow... You guys are really way out there. I have a 45gal Tank in the bed and a 38gal OEM. I have an electric valve that I use to change tanks from the inside of the cab. It also changes the fuel gage to the same tank I am running on. From my habits I grew up with in Wyoming, I don't worry about gas mileage, I always look for fuel when I get to 1/4 of a tank.

To many variants to cause it to change. Climbing, going down, into the wind, flat ground and such. Calculating fuel mileage is useless to me because on the same road depending on the weather conditions it could change drastically. I met a guy that was on the side of the road. Picked him up to go get fuel. He traveled the road all the time pulling his trailer and always made it. This time he was running into a very strong head wind and ran out of fuel.

I figure about 10mpg pulling my 5er and about 18 with out it. When I get to 1/4 of a tank I switch tanks. I never fuel up with the 5er in tow. If I am full on fuel I always run first on my 45gal tank and switch to my 38gal when I get to the 1/4 mark. If I have switched to the OEM tank I always fuel up the night before we leave so I have two full tanks.

I don't know how you can calculate your fuel mileage and use to 0.5 gal.

Intresting thread though...

Respectfully..
BC

 

[scottyb]

Wow... You guys are really way out there. I have a 45gal Tank in the bed and a 38gal OEM. I have an electric valve that I use to change tanks from the inside of the cab. It also changes the fuel gage to the same tank I am running on. From my habits I grew up with in Wyoming, I don't worry about gas mileage, I always look for fuel when I get to 1/4 of a tank.

To many variants to cause it to change. Climbing, going down, into the wind, flat ground and such. Calculating fuel mileage is useless to me because on the same road depending on the weather conditions it could change drastically. I met a guy that was on the side of the road. Picked him up to go get fuel. He traveled the road all the time pulling his trailer and always made it. This time he was running into a very strong head wind and ran out of fuel.

I figure about 10mpg pulling my 5er and about 18 with out it. When I get to 1/4 of a tank I switch tanks. I never fuel up with the 5er in tow. If I am full on fuel I always run first on my 45gal tank and switch to my 38gal when I get to the 1/4 mark. If I have switched to the OEM tank I always fuel up the night before we leave so I have two full tanks.

I don't know how you can calculate your fuel mileage and use to 0.5 gal.

Intresting thread though...

Respectfully..
BC

To me, it's just a statistical curiosity. I don't even pay for my own fuel unless I'm on vacation. Just like any statistical analysis, it's has less value with only a small sample. Much more meaningful if taken over a long period of repetative driving. My reason of starting this was more about the margin of error in the data reported by the trip computer.

 

[dave10a]

My stock Ford is fuel milage is accurate and have found no need to add additional fuel capacity. If I go dry camping in the hills I do carry an extra jeep can just in case, but other than that why add more fuel capacity?

 

[ncc1701e]

Stock tank and only option for my truck as configured from the factory was 26.5 gallons. Was a real pain when pulling. Really only wanted the Ford 37 gallon tank but Ford dealer would not install, but would put the Titan 50 gallon tank. So now I have a 50 gallon tank where the old 26 gallon tank use to set.

 

[jnbhobe]

I have the 38 gal stock and a 60 gal aux. I can fuel when and where I want without having the rig hooked up and can pick my price. I also don't pay for fuel unless I'm out of my local 100 mile radius. So I can leave with full tanks and return with empty ones. My truck also keeps track of the gallons used and its pretty accurate.

 

[dave10a]

I have the stock 26 gal fuel tank and have no problems. The fuel stops nation wide are easy to find and the fueling intervals are just right for stretching the legs and getting coffee or a soda. When I toured with a motor cycle, I stooped for fuel overing 150/200 miles and now with the truck its 250/300 miles. What is wrong with that? I can't see paying the big bucks to go 500/900 miles between fuel stops.

 

[rgwilliams69]

Depends on where you are traveling Dave. There are some runs we make where the fueling stops are extremely limited for a F350 pulling a 45ft coach that is over 13 feet tall. The extra money on the tank was well worth it for me just to not have to stop unless I wanted to stop. That and there are certain states I like to skip because of their fuel taxes on diesel. Even on the interstates it is a pain trying to get around the cars to the front pumps where I can use my credit card. If I go around back I have to go prepay (some states, some stations) because I don't have the trucker account numbers required to pay at the pump.

The titan 65 gives me 540 miles of worry free driving still leaving 45 miles reserve before fill-up. So unless I'm going multi-state I can just fill up when I leave and fill up when I get back, even for longer trips. Nice!

 

[scottyb]

Personally, I can't stand truck stops and the less time I spend at one, the better. The added bonus for me is, when at home, 400 mi gets me 3 days between fillups. 800 gets me more than a week. When I had the Chevy with the 60 gal transfer tank, I could almost make 2 weeks. I know I will be glad to have the Titan next month when I go to Big Bend.

 

[porthole]

Big advantage for us with the 65 gallon Titan is one of the few advantages for us "Jerseyites".
Fuel is typically the least expensive right here in our backyard.

On my 2100 trip to the upper peninsula and back, the lowest price I found was a Speeday at $4.00. the highest don't recall where but it was $4.46. Average seemed to be between $4.07-$4.20.

After dropping the boat off I filled up at a local station, 59 gallons at $3.76

For us, it means many of the camp trips I can go out and back with my current capacity, that makes the Titan installation a lot more palatable.

My GMC had a 26 factory tank, boy did I really dislike that, what a pain towing at 10 mpg.

BTW, Ohio still advertises bogus fuel prices on the turnpike. Diesel prices displayed on the big signs are without the tax we have to pay.

 

[porthole]

Looks like you ran the wheels off that boat trailer. :>)

Not quite.
When I arrived to pick it up the "might have a spindle issue" turned out to not having the spindle at all! I had brought a spare axle with me but the temp was -1 on the morning of the pickup. Without absolutley no help offered from the USCG personnel I elected to just pull the other side's good wheel and run with 4 instead of 6. 10K trailer and the boat was about 4K or less.

 

[scottyb]

What do you do with that thing. Looks like it could use a couple Yamaha 4-strokes.

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