Mismatch between real gas comsumption and average indication
 

I just bought a 2004 Toyota 4runner V8 with 24000 miles. (Canada- cold)

I use regular gas.
I filled up the gas tank and resetted the average fuel consumption.
I drove 158 miles 70% highway @ 55MPH rest is city driving.
I did 8 long stops (overnights and 10 hours during the day) and 40 short ones stop signes ...
The average displayed consumption was 18.4 MPG
I filled the tank at the same pomp and it used 10.4 G which averages to 15.3MPG.

This looks like a quite bad mileage. Also, I am comcerned about the variation between the dispalayed value (18.4) and the real one 15.3.
I have repeated the test again with similar results.

Can somebody clarify this for me?
I would be helpful to know how, what sensors are used to calculate the fuel consumption. Does it measure the fuel flow through the gas line, one cylinder, all cylinders?

Thank you,
Calin

I can't answer what sensors measure and calculate fuel consumption, but mine is off just like yours (reads higher than reality). It may look at the fuel pump flow or use the MAF and compare that with injector flow (this is all speculation on my part). It must use the odometer to calculate the distance part, and this must be legally accurate so the fuel piece is the one to investigate and go after. If I find out, I will let ya know.

Same here. Thank you.

Maybe it's a US/Imperial gallon thing. 18.4 miles per Imperial gallon (4.54 L) = 15.77 miles per US gallon (3.79 L), which is close to your actual 15.3.

Thank you Eric. I've got this confusion before when Canadian cars seems to be better than their US version :) But, because I could not belive such thing I've kept searching and found out there are 2 gallons units UK and US.

Unfortunately, this is not the issue for me. My car actually uses the international system. 255 KM, 39Liters of fuel average fuel consumption displays 12.8L/100km and the actual is 15.3L/100km. Because most of the 4runners on this site are used to the US system I have converted to US gallons.

I am into something promising. I have added to a full tank of 87 octanes an injector cleaner. I drove my car more aggressively and after half of tank it seems that the actual consumption is as much as it did when I was driving grandma way. The average displayed consumption is higher now. It is possible that my injectors where clog or I've got some carbon deposit. Anyways, I will confirm this when I stop next time at the pump.

This is a known issue with the 4th gen. :horse:

The fuel consumption figures displayed on the 4th gen 'Runners' trip computer are pure fantasy. My truck reads 10 - 15% higher than my figures calculated using the corrected odo reading and pump numbers. If you search on this topic, you'll find many posts affirming that this is indeed a problem.

Suggestions: First, check your odometer against a gps or known-good mile markers for a long stretch - at least 10 miles. Mine underreports miles traveled by 2.5%. Second, keep the tires inflated to 32psi (or whatever your truck says is correct). Soft tires can really suck up the fuel.

That said, 4Runners, with over two tons of mass and the aerodynamics of an open parachute, aren't economy vehicles. I'd not expect much better mileage than you report.

Good luck.

yeh i dont bother checking my avg/mpg gauge anymore. its never even close. i cant even get 300miles out of 20galons of gas. and i drive slow. i went to vegas from los angeles and it nearly took me a whole tank. o well. still love the 4r!

Do you have stock sized tires? I noticed that when I had stock tires my indicated speed was off from both my gps and radar speed signs. Once I upped to 265/75/16s my speedo now matches both my gps and radar signs almost exactly. This can be a contributing factor to the unreliability of the trip computer - I think I'm much more accurate now with the larger tires.

I was going to ask about tires also.
I switched to larger tires, thinking it would help milage. Instead it hurt the milage. Heavier tires etc. I used to be able to get 400 from a tank. Not any more. The cold weather really hammers it too.