How does your real MPG compare to the cluster display?

No funny business here coasting on a long downhill or following a semi super close, as I’ve seen some posts with a short trip and super high MPG readout. Not knocking it, it’s fun to cook the books sometimes! It’s entertaining to see those. We just drove from home in Detroit up to the Blue Mountains area in Ontario for the week for an anniversary trip. Pretty windy and plenty of hilly driving, plenty of miles on county roads around 60mph. Filled up once we got here and the tank took 7.95 gallons after driving 206 miles from my last fill up. Took a pic before pumping gas, displayed tank MPG is 24.6 but my actual MPG would have been about 25.9 according to my distance driven and gas consumed between fill ups. This has me curious; how big of a discrepancy are y’all getting between actual calculated fuel economy and the built in display?

 

Mine is not really close either. My distance to empty always reads around 340 and I always am getting over 400 per tank. I've learned to just run it and fill it when it's empty

 

My 'per tank' MPGs calculated by the truck are sometimes very close to the calculated and other times really off.
The only important gauge is the one at the lower right. The only accurate MPG calculation is the manual one done by dividing the miles between the last fill-up and the current one by the gallons required by the current fill-up.
Instantaneous MPG calculations done by the truck are really only useful to judge your driving style and how it affect overall MPGs.

 

About 0.5mpg.

Note that real MPGs will vary by tire size. That would not be accounted for in comparison calculations to the display, but to know your real world MPGs, you would have to correct for tire size. And, that can vary by about 3% for new versus min tread.

 

When I bought the truck new, it was a 175 mile drive back home.
65 mph on the freeway.
Indicated 26.2 mpg, which was awfully close to when I filled it up after the drive home.

 

I clearly don't like doing math as much as you guys.

 

Lol yeah I’ve never calculated it
My actual mpg? Less than i’d like…

 

It just can't be that simple. Are you certain this method works, or is it gonna get me in trouble if I just roll the dice and go for it?

Edit: Never mind, that's crazy talk.

 

With my tire size it's generally out by 1.5 L/100km fairly consistently after manually calculating it.

 

It depends how much you like to roll the dice? I haven't looked in a while, but my average fill up used to be over 18.5gal. Caught fumes a couple times.

Now that my work schedule changed and I can't hit the station first thing in the morning, I am got going as deep as I used to.

 

At home on flat roads I see an average of 15.5 indicated, which is usually within .5 of hand calc'd. 90% of my driving is 65-70mph. Keep it under 65 and it gets better.

I get quite a bit better mpg's when in mountains or hilly areas. I'll see 17+ in the mountains, even at freeway speeds. As soon as I'm back to flat lands my mpgs drop.

 

Dashboard is estimates. Gas-added-after is real. Use the "instant MPG" to try to keep the estimate closer to 30, slowing down below 75-80, coasting into red lights instead of accelerating, etc.

 

I live in southern Louisiana. Really flat, hot and humid. Don't know those last two things matter, but there ya go. I never manually calculated to know the accuracy, but when I fill all the way up, my screen tells me I have about 310-320mi in the tank. Most of my driving is road, street and highway with some interstate here and there. It varies from trip to trip, but I'd say I'm averaging around 18.5mpg. That's in my 23 TRDOF with the V6

 

~3200 miles round trip from PNW to SW US and back...
Used actual mileage and gallons pump over pump fill up data... 2020 TRD OR, total stock, with tannaeu cover: 24.xx mpg round trip, never worried about it since

 

Mine reads about .5 MPG optimistic.

 

How do you confirm your odo reading is correct to do the manual calculations? Fill until it overflows, or just til the nozzle clicks off?

 

I do the math every tank. I also have a ScanGuage going. Trucks computer is very accurate so far.
Most roads are 40 mph, a few areas of 50. When I take longer trips the MPG goes up but then I kill it moving trailers or driving on the dirt road I live on.

Overall average of all that, so far, 23 MPG says the computer And my math.

 

How is the truck calculating MPG?

Is it calculating off stock size tires and revolutions to give it a revolutions per mile equation?

Let's say, as most of us are rocking larger tires than stock, wouldn't we actually be getting slightly better mileage than what's on the display?

I might be missing something pretty basic as I don't know how the truck estimates this number. I never seem to drive till empty to get the manual numbers crunching. Luckily, I'm not planning a trip to the moon or anything, so I don't have to have any exact real-world MPG, but it's just something I think about on longer, boring drives.

 

I think it calculates with stock tires in mind. Bigger tires weigh more. They make the truck " struggle" a bit more cause the mpg to drop

 

My mpg is pretty close, probably within 0.5mpg, but it probably helps that I have larger tires. I had a recent tank that said 8.7mpg (Tucumcari to Amarillo, IYKYK) but hand calculated was almost 10mpg.

The "miles to empty" is wildly optimistic though. It can say I have 120mi to go, and 30mi later it says I have 60mi to go.

It's not too hard to find calculators for tire size and correct your miles by 7% or 10% or whatever is appropriate.

I think as long as you're consistent, it probably doesn't make much difference how you fill it up. When I had a diesel, I would fill it up until it was almost overflowing, let the foam settle, fill, let the foam settle, fill, until it couldn't take another drop- but on most cars that will damage your vapor recovery system, so now I just fill until the first shut-off, count to five, and click it on one more time until it shuts off.