I know it sounds odd. I do a bi weekly run to the next town . Avg is 1/4 tank there and back doing speed limit. Swapped from 195/70/14 to 15x7 z28 rims, front is 215/60/15 rear is 245/60/15. Drove car there and back 1/2 a tank. Never have I seen a gas tank empty as fast as that unless it was my 455 trans am or cutlass also with a olds 455 under heavy throttle. Am I missing something? Surely there can not be that much resistance.
fuel mileage nearly cut in half with tire swap?
- Thread starter wyldcdn
- Start date
- Status
I've found that my car will get worse mpg on certain fuels, also u might've got into it more this time around? Wouldnt think tires would make much of a diff.
Your new wheels are heavier and wider ( more friction ) so to an extent, I could understand a LITTLE less milage with everything else being equal BUT everything is NOT equal. Your new bigger wheels are taller which effectively reduces your gear ratio, so your highway milage would actually be better. So I think you have something else effecting your milage as I can't see it possible for it to be your wheels.
Larger or smaller wheels & tires than stock = inaccurate speedo/odometer, which will result in an inaccurate average calculation.
Drive down the highway at a steady speed and have a friend write down the mileage at each mile marker.
Drive down the highway at a steady speed and have a friend write down the mileage at each mile marker.
Blake442 said:
That was my first thought, but he is driving a known distance, and comparing the AMOUNT of fuel, so that theory does not hold. (1/2 tank now compared to 1/4 tank before) for a fixed distance.
Theres all sorts of things happening here. The larger tire will reduce your RPM on the highway, so it should improve mileage a bit. But they are larger tires, and heavier to turn so start stop driving would make it a bit worse. The z28 rims are aluminum in the 80s, and steel in the 70s, which ones are you talking about? Heavier would be worse.
Also, the new tires sound like its given you a bit of a "rake", so your drag is a bit worse. Even a little bit of change in drag requires alot more fuel. All that being said, your fuel mileage should not be affected that much.
Im questioning your measuring method. How did you get 1/2 tank +/- 0.25 of tank??? Sounds kind of inaccurate, like a few gallons inaccurate.
The ONLY true way to measure the amount of fuel used is to fill up the tank to the top, till you cant get fuel in anymore, drive your distance, fill it up again to the brim and note down the fuel you put in. Compare that to the distance driven.
Anything else is just a guess. In metric, cuz were in Canada, 1 L, or 10kms driven can change the L/100km by almost a full point. Thats atleast 1 mpg. It doesnt take much.
you can also get a better estimate if you use a GPS to measure the speed
Measure the speed while @ 50 or 60 mph on the GPS and what the speedo says. find the percentage difference between them and take the milage and multiply it by that percentage and that should give you a reasonable mileage estimate
Measure the speed while @ 50 or 60 mph on the GPS and what the speedo says. find the percentage difference between them and take the milage and multiply it by that percentage and that should give you a reasonable mileage estimate
As other's have said you need to measure this more accurately than just looking at the fuel gauge.
But yes, tire size can and will affect fuel mileage.
My truck came stock with 275/55R20 tires. I replaced them with 305/50R20 tires.
The tire height between the two was within .10" but the wdith was obviously a lot greater.
With no other change to the truck my mileage dropped by 2mpg or so on average.
But yes, tire size can and will affect fuel mileage.
My truck came stock with 275/55R20 tires. I replaced them with 305/50R20 tires.
The tire height between the two was within .10" but the wdith was obviously a lot greater.
With no other change to the truck my mileage dropped by 2mpg or so on average.
- Status
Similar threads
