MPG/DTE - Real life versus the Trip Computer

I’ve had many cars, and over the years most Trip Computers have gotten better at predicting Distance to Empty (DTE) and MPG. But the Bronco in my experience seems to be 8-9% under reporting (for example my lifetime MPG is 16.9 based on fuel consumption versus 18.1 in the computer, or about 20 gallons less)

My last fill up was very typical of this (see pictures)

So I got 265 miles on this tank, and I had 9 DTE. I put in 15.7 Gallons. That’s 16.88 MPG. I should have gotten 285 miles if I ran the tank bone dry. So that’s 11 miles under 0 or about 2/3rds a gallon left in the tank.

The trip computer hilariously calculates this to 18.1 MPG. That’s over reporting by 7%

My Focus ST was a little off on MPG, but DTE was dead on (in fact it once ran out of gas with 6 DTE). My Explorer ST was also a little off, but never more than .3 MPG (it got around 19 MPG so about 2%), I never let it get to empty so not sure on DTE (calculated it was close, maybe within 5 miles). My Corvette is nearly dead on every time for MPG, I just trust the Trip Computer in that car. I rarely check it now. I never have ran that super low on DTE either, but the calculation always works out within 1-2 miles.

It’s just weird how bad the Bronco is. Granted I have a 2-door, maybe the 4-door is better?

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I have only checked mine a few times, it wasn’t off my much 2-3%. I should probably check again.

I saw a YT video where the guy got almost 40 miles past zero in his Bronco.

He says in the video he’s going slightly downhill. I figure that’s a major contributing factor. It’s also what got me to try and run mine to empty a few times. I got about the same both times (10 miles past DTE based on MPG and fuel put in). That last time I ran the DTE to 4.

Car companies typically slightly overestimate by a couple of percent with cluster fuel economy and then each individual unit can deviate +/- from that. 8-9% optimistic seems like a lot, how often have you done your own calculation vs the trip timer? In winter the fuel blend at gas stations is normally different than summer although I’m not sure how the cluster software is set up to handle that change. I might do some digging on that and see what I can find

I do spot checks at every fill up (do some quick math, like miles traveled divided by gallons put in). But rigorous checks? Almost never, when the math on my spot checks always seemed an MPG off the computer I started to look into it more.

My Corvette for example says it gets 20.0 MPG (47k lifetime on the trip computer). My individual tanks vary but lets say I put in 14 gallons, I’d expect that to be 280 miles. If the fuel pump says 14.2 and I got 281 miles I say OK that’s decently close, no worries (I’m looking for being close to 285 at 14.2).

I’ve done this on every car since my Saab.

I haven’t tested it this far, but I have driven at least 15 miles after showing 0 miles to empty.

My Corvette will be out shortly so I’ll be tracking it more closely this summer. But the Bronco is still about 1 MPG over in the trip computer versus real life. The DTE even seems to agree somewhat. The tank is 16.9 gallons.

Assuming that you get 10 miles DTE under 0 (which based on two tanks I ran down to near empty was the case) a DTE of 280 means 290, which divided by 16.9 is 17.1 MPG a far cry from the computers 17.6/7 that it shows on the main Fuel Economy screen which I’ve never reset (or 17.9 on my Trip 2 which also has never been reset).

Now being generous and assuming a full gallon at a DTE of 0, then the math nearly checks out. A DTE of 280/282 matches the computers Fuel Economy screen of 17.6/17.7. However the per tank calculation is off. So maybe as the car gets more miles on it the Trip computer gets “smarter” as I allow it to collect more data.

I’ll post more as I have available. It’s just odd, seems like its still being a bit too generous. A co-worker of mine keeps insanely detailed records for his Bronco, maybe I’ll ask for his spreadsheet.

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Here is his spreadsheet (or a picture of it)