Is my truck lying to me - 21 mpg on the way home today

I filled up with Costco premium 91 octane fuel today and my truck says I averaged 21.7 mpg on the way home. This was in 70 degree weather on the highway, a 40 mile trip and 5 miles were going down a mountain pass. Oh, I am running Terragrappler 33" E rated tires with @ 36 lbs pressure.

 

Ah yes, the good old lie-o-meter in the dash...

 

With that combination it’s probably more than 23 mpg


Science














this is a 3rd gen worthy post. Show them how gen 2.5 does it

 

Top off the tank and run some pencil math. That’s an easy way to see if the dash is telling lies. Getting 21 mpg on the instantaneous readout? Easy. On the average? Maybe. Our sequoia has done 21 or close to it on a few legs of a trip.

 

I’d easily believe that for those 40 miles. Now make it a return trip and and enjoy a slice of reality.

 

Why premium?

 

I have got 21 MPG on a road trip. That was on a full tank.

 

I believe I get better mileage with it. That might be false though and not worth the extra cost.

 

I frequently get 19-20mpg on a 60 mile trip running mostly 65 mpg. Going over 70 really sinks mpg's on these trucks with poor drag/aero.

 

It is false, and there is no reason to buy higher octane fuel unless your engine requires it. Waste of money.

 

I guess it depends on fuel prices where you live but here it costs 25% more and there's no way it makes that much of a difference (if any).

 

Yeah all it does is resist detonation more than 87 octane, doesn't burn any differently. In a modern 10:1 compression engine there's no need for anything over 87. 12:1 or boosted... Probably safer to go 91+ to reduce the chance of pinging

 

I get very similar results. 60 to 65 mph gets me about 19 ish. I usually set cruise control at 68 with consistently gets me about 18ish unless it’s very mountainous. I found any faster than that the mpg’s drop off a cliff. In flatter terrain it does not drop off (over 68 but especially over 70) a cliff but a small mountain…

Anything over 70 absolutely destroys the mpg’s in these trucks IMHO. But I completely expected it before I purchased it, simply based off its size and weight.

 

The dash isn't always completely accurate. I got this drafting a semi on the highway on a long road trip. The amount I paid in gas said otherwise.

 

28mpg - "Here I Come"

 

More like 2.8mpg if you're gaining elevation

 

Your computer is usually wrong because I think most trucks have the speedometer off slightly to show a higher speed. Example is that my truck has stock size tires and it consistently shows that I am 2 mph over what my GPS says. So with that in mind, the truck thinks you traveled further than you actually did so the result is the computer showing a higher mpg.

 

From a summer road trip, truck calculation and hand calculations

Not bragging or trying to prove anything, just posting mpg info. No set fill up miles, just whenever we stopped for the bathroom,food or leg stretch.

Start Monroe CT

156.4 miles 8.847 gal 4.779 $42.28 Calc mpg 17.67 Truck calc 18.8 Bloomsburg NJ
211.1 miles 10.652 gal 4.459 $47.50 19.8 19.7 ?
281.8 14.472 4.899 $70.90 19.47 19.3 ?
173.2 8.941 4.599 $41.00 19.43 19.1 Lumberton NC
303.1 16.77 4.399 $73.80 18.07 18.9 Brunswick GA
268.5 14.237 4.699 $66.90 18.86 18.7 Tarpon Springs FL
198.0 12.673 4.419 $56.00 15.6 16.1 Sebring Fl

Return to Lake Luzerne NY

260 14.450 4.699 $67.90 17.9 18.0 ST augustine Fl
221.2 12.954 4.799 $62.17 17.1 18.1 Yemasse SC
241.5 13.333 4.399 $58.65 18.1 18.6 ?
213.9 11.058 4.499 $49.75 19.34 19.1 VA
255.9 12.259 4.749 $59.50 20.87 21.0 Jonestown PA
364.2 19.437 4.759 $92.50 18.7 19.5 LL NY


$855.63 dollars for 170.056 gallons and 3,148.8 miles.

For whatever this is all worth, but I just wanted to give you some useless information.

 

I thought that too until I got a ticket for doing 81 kph in the 70 zone. I figured I was good because at 81 on the speedo, I should have been doing 79.

 

Interesting......maybe radar guns are also over by a few mph in order to generate more money ><

 

I'm a new Tundra owner, 2020 Crewmax, and I've been driving quite consistently between 16-18MPG without trying very hard. This is with plenty of hills, passing people when I need to, any otherwise driving responsibly. (Rolling towards lights, predicting stale lights, not racing the clusterfucker of idiots tailgating each other on the highways, etc.) and that is with me doing actual "truck stuff" regularly

 

I believe radar guns have to be calibrated after X time frame. Not sure what it's calibrated to though...

 

My figures were from a 90% highway trip down the East Coast. I do agree, if you are mindful,the numbers can be very favorable. When I do truck stuff, I get truck MPG's !

 

True, but like any calibration, there is a range of acceptability, and you bet your ass they "prefer" the calibration house to do it on the high side.

 

what amazes me is that even when driving down into a Valley, little if no gas pedal at all,
and I got 9.9 l/100 kms = 24 mpg.
My wifes Outback is still better at 7.7 l/100 kms = over 30 mpg average all the time.