Don't Trust Your Truck's Mileage Computer

Mileage group 2 II

Pickup trucks have had mileage computers onboard for as long as manufacturers have known customers want to keep track of how much fuel they're using. Unfortunately, those computers aren't as accurate as you might think.

According to the Detroit News, there is usually a small difference between what the internal vehicle computer calculates and what you might calculate for yourself by keeping track of your miles driven and dividing that number by the number of gallons put into your tank at your next fill-up.

It's been our experience, with rare exceptions, that the truck's computer is optimistic about how many miles per gallon it is getting at any given moment. Additionally, if you tow or haul the computer could be adjusting for that in the overall calculation, which could also give you an unrealistically good readout. We've noticed that several truck makers are starting to offer specific adjustments to the trip computer that help the mileage calculator record and present a real-life fuel economy readout by allowing the driver to select what kind of work or towing is being done. This allows the computer to more accurately determine mileage and how many miles to empty.

Check out your own truck's computer setting to find out if you can make adjustments before a big trip so you can more accurately keep track of what your fuel costs might be. During our 2013 Light-Duty Challenge we found five out of the six tested trucks had computers that reported better fuel economy numbers than we calculated ourselves — one by as much as 12 percent. We assume that as truck computers get smarter and truck owners are allowed to input route-specific information these types of discrepancies will go away.



I think you're confusing MPG and MTE. The adjustments for type of driving are to more accurately 'predict' MTE, since it uses a history of your past driving. If you hook up a heavy trailer and start towing, your MPG will be much lower of course. But your MTE calculator is still using a larger historical db to predict MTE. Since that includes mostly non-towing miles with much higher MPG, your MTE cannot be accurate. So, adjust the settings so it knows you want to use towing MPG to predict MTE and it becomes much more accurate. Changing settings will not affect your MPG. That is based on factual data and not predictions on how the truck thinks you might drive as the tank empties.

All this technology yet absolutely zero improvements to the MPG itself.

Between the bogus mileage computers and fuel gauges where 75% of the fuel tank capacity is displayed in the top 25% of the gauge, I guess they take us for a bunch of dummies.

It's worth mentioning that one should also test their Odometer and Trip meters with a GPS before relying on them for any sort of calculations. They are not always accurate. Especially as tires wear or if one changes to a larger tire size.

I have to say, my 11 Ecoboosted F-150 lies to me as well, tho in the positive direction. My last tank, I drove to OC MD, I went 477 miles and added 22.7 gallons of mid grade fuel (I always use Mid, 89 octane) that equates to 21.01 mpg, yet my meter read 20.7 mpg. I typically do the calculation on every fill up, or a least every other, and this happens more often than not with my truck. By the way, 21 mpg in a Supercrew FX-4 w/ 3.73 rear, 6.6ft bed, not bad at all!!! Thats with four people and we each had 2 weeks of gear in the bed, traveling 70 pretty much the entire way, with a/c on recirculate.

My 5.7 Tundra's MPG readout is anywhere from 12-14 MPG's (calculated MPG is usually within .5 MPG's of the readout) since I added my 35" tires, lift, front and rear bumpers, and a winch. I added the Hypertech speedometer recalibrater to make sure my speedo and odo are accurate to the increased tire size (confirmed by GPS). Not bad for adding roughly ~400 pounds and 35" tires all with factory gears (4.30).

@ MatthewJohn: See, that is what's amazing about the pickup trucks now. If I bought a brand-new pickup from any of the Big 3 and used it the same as I do my '02 Mazda Tribute (roughly 65% highway/35% city), I would get the same mileage! Now if I just had $30K+ lying around...

But I thought the FX4 package was only available with a 4.10 rear end. Somebody want to clear things up?

@ John: The Tundra is available from the factory with a 4.30 rear end? No reason people complain about poor mileage. Bet it's real nice for off-roading, though, and from your accessories it sounds like you do a fair bit of that. Hope you have fun with it.

And actually on-topic: YOU DON'T SAYYYYY? There's a reason we call it the "lie-o-meter," and why all our family members take the time to write down the exact odometer reading and the exact gas pump reading.

In news that should shock no one, on-board mileage computers are unreliable. Notoriously so.

The only reason this is news IMHO is that so many people don't do math. If you reset the trip ODO every time you fill up, you can take the total mileage driven after the last fill up, divide it by the number of gallons you added to your gas tank, and come up with a very accurate MPG. Then reset the trip ODO and repeat.

I've been "calcuating" my MPG this way for years, mostly because monitoring MPG between fill-ups is a quick way to spot a problem. It's something I learned to do when I was 16. If only everyone's dad had taught them this trick...

I have always found our computer readout to be off too. In our Prius (I know not exactly a truck) the mpg's have been off almost exactly 3 mpg since we bought it in 2009. It has never deviated from this amount.

I always calculate by hand and have a consistent place I fill up and a consistent routine when I fill up so I think I am pretty spot on in how I measure. I wonder why a computer can be so far off unless it is to fool drivers into thinking they are doing better than they are.

My 2005 Ram got 12.5 mpg pretty consistantly (80 city driving with a 5.7 hemi and 3.92 gears on a 4x4) and the computer was within a 1/2 mpg of this everytime.

I calculate my mpg every single time. The MPG meter on all my vehicles has always been wrong. It annoys me that it's even there because I know it's wrong. Usually over-stating. Often by 2-3 mpg. And I agree to check your odometer. I've been shocked at how far off some can be even with totally stock everything. FX-4's come with 3.73 Elrctronic locking rears....even my 05 has a 3.73 in it.....I have been walking dealership lots tho and I have been seeing FX-4's come with 3.55 Electronic locking rears.....must be something they started for 2013. I was pretty surprised to see that, and actually all 5 FX-4's they had at that dealership (Winner Ford in Cherry Hill NJ) all had 3.55's.

People are lazy and or stupid, its takes two seconds to dived gallons put in by miles driver. I never trust the computer.

I would attribute more error to the actual measurement of the gas. Filling the tank until the pump stops is not going to give you the exact same amount every time. In addition, how accurate are the fuel pumps? Unless you are measuring the gas by hand, and can see exactly how much gas is in the tank, a 5% difference could easily be attributed to errors in measurement.

In the past week or so:

GM has released the power and torque ratings for the new 6.2, GM has unvailed the new Tahoe, Suburban and Yukon, Ford has built it's 2 millionth ECO boost and Toyota has built it's 1 millionth truck in Texas.

And this is the only story you guys have had since the 14th.

@Voltage - Gas pumps are supposed to be tightly regulated and certified verifying their accuracy within 0.3%

I'm with Hank. Never have trusted those mileage readings on my truck. I've had a lot of incidents where I tested it with my own knowledge and it was way off. I filled up on a trip this summer to Florida and the reading said I was good for 375 miles. I kept watch of it as it would count down miles. My tank was empty at 325 and it kept on saying I had about another 75-80 miles left on the tank. Don't be a dummy, too many factors contribute to mileage and computers aren't quite there at figuring it out yet.

You can get the 4.10 gears on the FX4 with the Ecoboost, I've built one before on the website. I was only available with teh FX4 apperance (sticker package and black rims) option. Looks like Ford has broaded out of that package, but still only available as an option on the FX4 with the Ecoboost.

@David The 4.30 gears are great, not only did I save ~$1,500 dollars by not having to regear like my other friends, but the truck will still move out nicely with those big 35s. 4lo, put the truck in first gear, and I can crawl for days.

I had checked the reading on my last GMC (2008 1/2 ton 2WD 5.3L) and found that much of the time the reading had been very close; actually within tenths of what I calculated at fill-ups. I also found my previous F150 to be quite accurate too; perhaps much of this had to do with consistent driving routes and habits which worked best with the means for calculating MPGs.

I suppose to be truly accurate, you would best measure distance with a GPS rather than the vehicles slightly inaccurate odometer (which the trip computer collects its data from). I don't even have one in my truck, so I don't get to reset every time I get on the freeway or coast down a hill and ignore the heavier fuel use when accelerating. So I can only report an honest 13mpg average for my 2005 F150 5.4. It's terrible! Though most of that is putting around town. Still no excuse.

@Voltage, why does Mark owe you stories? Are you paying to use this website? I would like more stories too, but I certainly don't feel entitled to them. I better not create any websites, the world might expect something of me!

Wait, I must be thinking of the Raptor. That makes a lot more sense--I can't think of any reason anything besides a dedicated off-road pickup should come with more than a 3.73 rear end.

Anyone remember when you could get the lowest-spec half-tons with, like, a 3.08 rear end or even lower, like 2.73? I hear those were great for MPG's (somewhere in the mid 20's or higher) but once you got to 55 mph, your engine was screaming.

I have seen the trip computer on my Subaru top out at 76mpg. It takes a reset at a 3 mile long hill and nearly coasting the entire way to reach this mpg. Mpg goes down quickly after that as I trudge up the next hill.

@maxx What are you smoking? Truck mileage has improved enormously during the last 25 years. My half ton does almost as well as my old sedans and compact pickups did.

My 1978 Dodge 1500 tradesman only got about 10 mpg city and about 16 highway. Today's vans are getting much better than that. My 2009 Silverado reg cab gets 22 on the highway.

@ David

RE: Tundra 4.30 gears


the tundra has very high transmission gears to compensate for the 4.30's... in fact a 3.73 F-150 has a lower overal drive ratio in most gears than a tundra with 4.30's.... Nissan Titans are the opposite, very high rear end gears and low tranny gears.


I find that if I go on a long trip, my fuel consumption readout becomes more accurate. I don't believe it around town.
It should give a "realtime" readout like gallons per mile or litres per km not an estimate of MPG.

I don't thing is only the computer lies about fuel for ford,,ford are the best to lies about the fuel.....

my onboard was optimistic most of the time when talking mpg, but yet the DTE errored on the other side, telling me I had less then I had in the tank.

An indicated 20.3 running on Murphy Usa cheap 87 octane in the hills of southwest Missouri aint bad at all, a realistic 19 something mpg, going 65 mph up and down some of the steepest hills.

Does the new Gm not have a bigger tank option then 25.9 gallons? It's kinda funny if that's the way it is, after seeing their commercial showing the Silvy and the F-150, and the Ford out of gas. The bigger tanks on Ram and Ford will beat the slight advatage Chevy has. Maybe the Chevy commercial will start saying "best gas mileage for a v-8, with less torque?"

^ please learn to differentiate "then" from "than." It reinforces your claim that "people are totally clueless" and lowers your credibility on pretty much everything else. Putting spaces in between words also helps!

@Alex - You may end a sentence with a preposition. Just do not use extra prepositions when the meaning is clear without them.

That is something I cannot agree with.
That is something with which I cannot agree.

Where did he go?

Where did he go to?

Where did you get this?

Where did you get this at?

I will go later.

I will go later on.

Take your shoes off the bed.

Take your shoes off of the bed.

You may look out the window.

You may look out of the window.

Cut it into small pieces.

Cut it up into small pieces.

@ Alex - looks like the fake Lou is trying to school you.......... odd how his post comes after you critiqued a Rambo Goat Herder comment.

Here is a bit of news for you GMC guys desperate for something new:

"The national Canadian and provincial Ontario governments have agreed to sell 30 million shares in General Motors that they received in exchange for their contributions to the 2009 bailout of the automaker. The shares are worth about $1.1 US billion, and were purchased by the Bank of America and the Royal Bank of Canada as a block.

The transaction will be completed early next week. The sale reduces the Canadian governments’ stake in GM by 21%, down to 110 million shares. Canada and Ontario had been, since the bailout, the third largest stockholder in General Motors, behind the UAW and the U.S. Treasury, and after the sale will own about 8% of the company’s shares.

“As we said from the start, our investment in GM was always meant to be temporary as we worked to maximize the return to Canadian taxpayers,” Finance Minister Jim Flaherty said in a statement. “The government of Canada is committed to exiting from ownership of GM as quickly as feasible, while maximizing the return for Canadian taxpayers, as we demonstrated today.”

The banks purchased the shares at a discount from Tuesday’s closing price, $37 a share, up 28% from the start of 2013."

You know what is ironic?
Canadian governments offload 1.1 billion in GMC stock and then they turn around and agree to chip in 135 million as part of Ford's 700 million investment to upgrade its plant in Oakville, Ontario Canada.

Get rid of GMC stock and invest in a Ford plant........ Ouch.

@Lou, "that" could be considered redundant, but I do not believe that it was incorrect like the examples you gave. Is this what you are referring to? I suppose if you want to be pedantic, I didn't capitalize the first letter of the first word.

Lou BC, I didn't think that was you. He sounds like a freshman who wanted to share what he learned at school today. :)

@Alex - freshman?

You are giving him way too much credit.

I meant 9th grader kind of freshman, but still WAY too much credit!

@Alex - true.

Freedom of speech means nothing when that freedom is twisted into a perverse distorted form used to stifle free speech of others.
Ridiculing and defaming others while hiding under a veil of anonymity is cowardice in its lowest form.
Those people spit on the graves of the glorious dead who defended our freedoms.
Free speech is completely wasted when one no longer is able to discern what is true.

Welcome to

The bottom line is Lou gave up the name so he doesn't have any claims to it anymore. Also, when a person enters comments on a blog for the purpose of public display, he is giving an implied license at least for that display and the incidental copying that goes along with it.

Lou could be in the wrong for copyright infringement though. He copied a long portion of a news article or from someone else's blog and gave no attribution to it. This is called copyright infringement. Not that others haven't done that before, but you should try not to do that.

Lou is using copyright infrintement to troll GM fans.

Welcome to

In another publication I read that the computer does not actually measure the amount of gasoline that goes into the engine but calculates how much is needed based on data from the MAF. This would mean that there could be several sources of error ranging from varying amounts of alcohol in the gas to vacuum leaks to humidity changes. Just the nominal 10% alcohol added to fuel could cause your computer to overstate mileage by 3% or more. I would like to see an article on the sources of error and how significant they are. I did find a station that sells pure gasoline and it seemed to improve my computer's accuracy.

@Alex I never said anyone owed me anything... I would simply adding a counter point to the story. Anytime you only look at one side of things, you aren't getting the whole story.

The bottom line is that Ken gave up the name so he doesn't have any claims to it anymore. Also, when a person enters comments on a blog for the purpose of public display, he is giving an implied license at least for that display and the incidental copying that goes along with it.

Ken could be in the wrong for copyright infringement though. He copied a long portion of a news article or from someone else's blog and gave no attribution to it. This is called copyright infringement. Not that others haven't done that before, but you should try not to do that.

But you doesn't have to call me can call me Lou or Lou BC or LOU or Ken all the

If I knew what I was actually talking about this statement would make

Of course it's inaccurate. So are the mph and odometer gauges. There's many factors including factory calibrations that enable warranties to more quickly cease. Cha-ching...

I have to agree with the folks that experience the under and not the over on fuel mileage.
My 2010 Ford Focus shows 39.5-40.5 mpg but actually shows about 1/10 to 2/10 less per mpg when I calculate on a calculator.
The sticker shows I should get 24 city-35 hwy. I've got about 1/2 gallon to 1-gallon fuel when it shows I should be empty.
The driver and his/her driving habits make the difference.....
I would think pick-ups are experiencing the same as my car.
Only the above applies when the truck is empty. Which applies 90 plus% of the time.

'06 F-150 SuperCrew 6.5ft box, 5.4L w/3.73s.

I have calculated the mileage myself at least 10x in the last 5 yrs of owning it. Every time it has been within +/- .1 L/100km.
I'd say that my mileage calculator is deadly accurate.

@Mike - really, my F150 is never that accurate.

If your F150 is like mine, it does not read litres per 100 km down to a decimal point. It rounds off to whole numbers.

Nice try though.

anyone who is tired of the trolling can click the "contact us" link at the bottom of the page and file a complaint.

or click here.

My 2005 F-150 Lariat MTE was working great until this last week. I went to my dad's for dinner which is about 30 miles away making it a 60 mile round trip. My MTE said I had 99 miles left. When I got there it said I had 56 miles to empty. On the way back before I got half way it said I had 19. Then a few miles down the road it said I had 7. I got off the freeway at 5 miles to go and the nearest Costco was about 3 miles. I nursed it down to the station and it said I had 2 miles left. Now my truck gets about 13 mpg in the city and 17 on the highway. I put in 6 gallons to clear the low fuel warning which should have given me a reading of about 102 MTE. By the time I got home about 6 miles away it said I had 46 MTE. Any ideas on what could be causing this?

@Voltage: Nice argument, but at least somewhat invalid. Every state has regulations about how accurate the pump meters must be and they are tested regularly for that accuracy. As such, the pumps are supposed to be accurate to about .01% in most states, if you bother to read the stickers on those pumps. That's in the vicinity of one teaspoon per gallon or MAYBE 1/10th of a mile for a truck.

Obviously the on board computer mileages are faulty. Its just due to the sensors from where it get fuel readings & also the odometer reading. Counting on GPS is more accurate & tamper proof; needs no re-calibration. and a pricey diesel level transmitter will give accurate mileage calculation on road.

if they put an item on a truck it adds cost to the vehicle. if the item isnt accurate then you are being charged for something that doesnt work

The comments to this entry are closed.