Bad Gas Mileage, or Faulty Guage

I recently bought a 2011 Tacoma TRD Off Road. It does have 275/70R18’s, but I can literally see the gas guage move even when driving conservative. The overall circumference between factory tires/rims is roughly 3”. Looking at a tire conversion chart, my speedometer should only be off about 5mph. I’ve seen some sending unit issues here on the forum as well. Any ideas? Would the extreme cold have anything to do with it? It has always been Southern truck, but it has been in the single digits here with wind chill since I bought it.

 

Winter blend will affect gas mileage also as the temperature drops your tire pressure does also leading to more rolling resistance and less MPG. The cold air is thicker too, more wind resistance, single digits means thicker fluids meaning more resistance so again a decrease in MPG.

Also check fuel filter, air filter, tire pressures, etc.

Welcome to TW by the way.

 

Absolutely. Extreme cold makes a big difference. My first winter with the iDatalink installed & it confirmed I'm burning some serious gas.

 

Thanks guys. Good to be here! I will check the air filter and tire pressures before going to the extreme with fuel sending unit issues. It has been maintained regularly at our local Toyota dealer, and had an oil change just before I bought it, so I would hope the air filter wouldn’t need changing. That would be the cheapest fix though. Again, thanks.

 

What actual fuel economy are you getting?

Those tires are significantly larger than 3” in circumfrence larger.

You have a larger, heavier wheel with wider and taller tires, and I’m going to assume a lift of some kind to fit them.

You will get shitty mpgs. Its the name of the game with big tires.

Test what your actual fuel ecomony is, and remember to multiply your odometer distance by the percentage larger in circumfrence the new tires are compared to stock in order to get the actual miles you drove.

I would expect your truck to get around 16 mpgs with those wheels an tires. Just a guesstimate.

 

You’re right. 8”. My bad. I’m getting about 14mpg it seems. The fuel guage will move a whole quarter of a tank in less than 20mi though is my concern. Thanks for the input, I greatly appreciate it.

 

After putting on my steelies and at tires for winter, and temps under 20 degrees , my first tank dropped 1.5 mpg. Garage kept, I don't warm up over a minute before driving.

 

The new tires are about 9% larger in circumference. That means you are driving about 9% farther than the odometer is reading and about 9% faster than the speedometer is reading. Speedo says 65 mph X 1.09 =70.8 mph. When you manually calculate your fuel mileage add 9% to the miles driven in order to get a more accurate mpg reading. For example if your trip meter says you drove 255 miles; 255 X 1.09=277.95 miles that you actually drove. Then divide by the amount of fuel you added to the tank. 277.95 miles / 18 gal = 15.44 actual mpg is a little better than 255 miles /18 gal = 14.1 mpg. Or you could simply multiply the mpg you calculate by 1.09 to get a more accurate reading.

You have several things working against you. Winter gas, cold weather, larger diameter tires which effectively change your axle ratio for much less power, heaver tires which rob power plus the fact that your odometer is off by 9%.

 

This is great info, thanks. It seems i’ll be lucky to even get 300mi out of this tank. Would putting 4.88 gears in the rear and help gas mileage any?

 

Dumb question, but does tire size throw off your odometer by the same ratio as your speedometer? Or in other words, if you’re actually going 2% faster than your speedometer says due to the bigger tires, are you also going 2% further than your odometer shows too? If so, isn’t your gas mileage better than what you’d think based on miles shown?

 

Boyk1182, you’re a Marine combat vet? Me too. 3/1 - 98’-05’

 

Yup I was in after you got out, E 2/10 OIF 2006-2007

It was a non-firing artillery battery at the time so we did convoy security.