MPG Variation

Got a question for the brain trust. I have a 2018 TRD ORSB V6 auto that has, from new, varied in mpg performance by a significant amount. I drive similar routes each day, driven the same way regarding throttle, speed, etc and I can vary from an average of 16.5 mpg one day to 19.5 mpg the next on the same tank of gas. I do have the OV tune (91 Base) installed but this made no difference to the variations in mpg -- although it did provide significant improvement in drivability. Since this is intermittent I was wondering if it could be associated with a bad timing sensor--ie gets a good solid signal one day and not so much the next. The truck is always smooth--just the mpg variation. Anyone else experience this issue??

Cheers,

db

 

How many miles are on it? Trans still learning?

Always check mpgs from miles driven and gallons filled. The computer is a terrible source

 

I have been testing machines for 30 years. I can guarantee you that, if human beings are involved, you cannot get any repeatability with a small sample size. Drive the same route 10X the same way same driver and it will not have the same outcome.
Drive it for a year, calculate the mileage by hand and at the end of a year with 50 or so data points THEN you will have a good idea of your specific average.

The reason is you think you are driving it the same way but temp, traffic, your foot, other traffic, time of day tire pressure (a psi makes a difference) and all kinds of other variables will assure that you cannot repeat your results with any degree of accuracy.

 

The gearing on these trucks make them very susceptible to wind, temp, and even the slightest incline. My best mpg is going 50 mph for 20 minutes non stop in warm temps= 28mpg. @ 68mph, I get between 23 and 25mpg in summer, I have the 6 auto TRDORAC

 

Around town or above 70mph = 16mpg

45-60mph cruising = 20+ mpg

(OVtuned)

 

I agree, mostly. The displayed MPG is good for some things.

The instantaneous MPG on the display is good for providing feedback on APPROXIMATELY what your fuel consumption is, at that point in time. The trip average is also APPROXIMATE. Good info, but not nothing to hang your hat on.

The tank average is the closest of all, assuming several things: You've gone through most of a tank before referring to it, and you fill to the same point every time being 2 of the most important.

Point is: The displayed MPG is useful only if you use it as a REFERENCE to help you monitor and hopefully improve your throttle habits.

 

Mine is a mt, but driving home from work i get anywhere from 23 to 28. The difference is what traffic i get behind and which red lights i catch.

There is one red light that if i catch it green i know I'm above 26 every time. If i catch it red i will be below 25. It has to do with that particular spot, how long the light takes the change and the hill that follows it.

And then if i get behind someone who doesn't carry momentum through corners and up hills i lose even more. On small trips (15 to 25 miles) small things make large changes

 

Quit depending on the dash for awhile, and simply hand calculate each total tank, and average at least a dozen tanks together. That will give you a much better view of your MPG than fractional tanks.

 

I posted about wind effect in this thread the other day. Working as designed

 

When I hand calculate at fill up it ends up matching pretty close the dash, last fill the dash said 21.6 and it calculated to 21.8.

 

The computer is pretty accurate. HighPSI is correct, you are not accounting for every variable. It does go to show how much of the fuel economy comes from decel fuel cut and how much energy acceleration takes.

My 12 mile commute varies by 3 mpg daily based on traffic lights and can vary by as much as 5 if I am driving more aggressively.

 

I also found the computer to be fairly accurate. Not saying the manual method is accurate, either. Unless you can see exactly where you're filling up to. I check manually occasionally for controls, then just rely on the computer.

 

Pay attention to how your driving affects the number but otherwise ignore the number. If you want to know if your mpg over time is stable, use the pump and odo readings and compare them over a full tanks usage. Extremely small variations in pedal pressure affect the instantaneous readings making them useful for training fine muscle control but useless for actual mileage. You may find the tank average display close enough to be useful but you may not.

 

Yeah, didn't make myself clear.

His problem for confusion is he's reading MPG for 'partial tanks', or let's call it 'that trip'. Not the actual MPG of the whole tank.

By knowing multiple tanks all averaged together you get a more helpful MPG. What you get on a 20 mile trip is pretty meaningless.

So. If the display can show the average for the tank (over multiple trips) rather than 'that trip' it might be more useful.

But it's why I suggested the hand calcs averaged over multiple tanks. Not because the computer is wrong, but because it displays something different than the way most folks think of how MPG is derived.

 

The long term average on the big screen is useful for long term trend monitoring.

You are correct, besides training yourself (which is a very good idea with these trucks) the instantaneous and trip numbers are too variable to be useful for monitoring.

 

My MPG varies greatly...when I let the wife drive the truck.

Right now I'm averaging 22.5 MPG using regular 87 gas. When I first purchased the truck I was putting in ethanol free and was able to pull 27 MPG. The mileage increase using ethanol free was not enough to justify the increased price per gallon however.

 

How far is the drive and how many lights are there? I only have a 4 mi drive to work but there are 4 lights and I see big variation depending on hitting those lights or not.

 

OP here. I should have provided additional info--truck has 15k on it and OV tune flashed many tanks ago so we should be past the major "learning". High altitude location (5k+ ft) and mountainous. Also, the mpg on the dash is fairly accurate -- I hand calc'ed my mileage at each fill up for the first 5k miles and the hand calc was always within 0.5 mpg of the dash unit--although the dash always showed the slightly higher mpg. The variation of + or - 3 mpg under similar driving conditions just seemed strange. I know you can not duplicate driving conditions perfectly but an 18% variation under similar conditions was, based on my life experience with 30+ vehicles (5 of which were Tacomas) just unusual . I was curious as to whether some malfunctioning mechanical or electronic device (timing sensor) could cause such variation without noticeable drivability issues???? As some have said--it may simply be that these vehicles are incredibly sensitive to minor changes in driving conditions--wind, load, throttle pressure, temperature, traffic, etc.

Cheers,

db

 

I'd suspect the driver's perception of the displayed numbers first.

 

With all due respect... this truck is designed for efficiency. Any, and I mean any, variation is going to change efficiency dramatically. If you have had 30 vehicles then you should know that some engines (chevy 350) just sucked no matter how hard you thrashed it or how much you babied it. This truck is opposite... you baby it and get real good mpg. You drive it normal and it gets not so good mpg. Drive it like you stole it and it gets horrible mpg. It's different but your results are also normal for this vehicle.