how to figure MPG
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how to figure MPG
I have a 1997 f 150. I went 1028 miles and used 55.7 gal of fuel, so I got 18.45 MPG by that figure. But stock tire size is 235 70 16. My tires are 245 70 16. How would I adjust the miles?
Thanks, Jeff
Thanks, Jeff
FTE Legend
Joined: Aug 2004
Posts: 37,887
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From: North Central Rural Sask.
Just wanted to add...
When calculating fuel mileage, make sure you fill your truck up to the brim, as in stand at the pump, and fill it till no more gas can enter the tank.
Next time you fill up do the same and you will get a much more accurate reading on your mpg, then filling your truck up till the pump clicks off.
On my honda civic (daily commuter car) if I fill the tank right to the brim, I can get an extra 200ish km's out of that tank, so that goes to show ya how you can get mixed readings unless you fill your tank to the brim each time, and figure the average that way.
When calculating fuel mileage, make sure you fill your truck up to the brim, as in stand at the pump, and fill it till no more gas can enter the tank.
Next time you fill up do the same and you will get a much more accurate reading on your mpg, then filling your truck up till the pump clicks off.
On my honda civic (daily commuter car) if I fill the tank right to the brim, I can get an extra 200ish km's out of that tank, so that goes to show ya how you can get mixed readings unless you fill your tank to the brim each time, and figure the average that way.
Senior User
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When it says you're going 60MPH on your speedo, you're going 61.1mph. So add that 1.9% to get your "true" MPG.
Just wanted to add...
When calculating fuel mileage, make sure you fill your truck up to the brim, as in stand at the pump, and fill it till no more gas can enter the tank.
Next time you fill up do the same and you will get a much more accurate reading on your mpg, then filling your truck up till the pump clicks off.
On my honda civic (daily commuter car) if I fill the tank right to the brim, I can get an extra 200ish km's out of that tank, so that goes to show ya how you can get mixed readings unless you fill your tank to the brim each time, and figure the average that way.
When calculating fuel mileage, make sure you fill your truck up to the brim, as in stand at the pump, and fill it till no more gas can enter the tank.
Next time you fill up do the same and you will get a much more accurate reading on your mpg, then filling your truck up till the pump clicks off.
On my honda civic (daily commuter car) if I fill the tank right to the brim, I can get an extra 200ish km's out of that tank, so that goes to show ya how you can get mixed readings unless you fill your tank to the brim each time, and figure the average that way.
Also you're saying you can get 200KM out of topping off? That converts to 124.27 miles. So assuming you're getting 35MPG in that civic, you can squeeze about 3.56 gallons extra in there? A bit of a stretch, isn't it?
Senior User
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I'm not a tire expert so I don't know for sure. Heres what I do know. The 245 has a 1/4 inch taller
sidewall than the 235. ( calculated by using the aspect ratios of both tires. ) But if the overall height of
the tire, center of rim to top of tread is the same with both tires. The two tires will travel in a circle in the same
distance. Thus your speedometer would stay the same.
sidewall than the 235. ( calculated by using the aspect ratios of both tires. ) But if the overall height of
the tire, center of rim to top of tread is the same with both tires. The two tires will travel in a circle in the same
distance. Thus your speedometer would stay the same.
Senior User
Joined: Oct 2008
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Two circles cannot have the same radius but different circumference.
Here's one of my favorite Tire size calculator
Here's one of my favorite Tire size calculator
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FTE Legend
Joined: Aug 2004
Posts: 37,887
Likes: 20
From: North Central Rural Sask.
and IF I remember correctly, standard deviation on those are less than quarter an ounce. That's part of the reason why these undercover specialists go inspecting fuel stations and issuing the blue star seal you see, verifying (in California) it's accuracy and functionality.
Not a stretch at all either, I put on about 65,000 kms on my civic a year, and about the same on my diesel f250, and I USED to do ALOT of highway trips of 5-700 kms a day(1-2 years ago i was putting on well over 120,000 a year), and I calculated my mpg frequently.
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From: NC
I'm not a tire expert so I don't know for sure. Heres what I do know. The 245 has a 1/4 inch taller
sidewall than the 235. ( calculated by using the aspect ratios of both tires. ) But if the overall height of
the tire, center of rim to top of tread is the same with both tires. The two tires will travel in a circle in the same
distance. Thus your speedometer would stay the same.
sidewall than the 235. ( calculated by using the aspect ratios of both tires. ) But if the overall height of
the tire, center of rim to top of tread is the same with both tires. The two tires will travel in a circle in the same
distance. Thus your speedometer would stay the same.
235 70 16 circumference is 28.953
245 70 16 circumference is 29.504
Difference is 1.9%.
Hotshot
Joined: Jul 2005
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a 245 tire is 245 mm wide and a 235 is 235 mm wide. they are both 70% side wall height. one tire is 70% of 245, the other is 70% of 235. the 70% is the same, but your multiplying by a different width to get the side wall height. that gives the 1/4 inch taller calcualtion.
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If the track the miles and fuel used over multiple fill ups, topping off the tank becomes moot, or nearly so. Particularly if you are consistent in your topping off practices.
You can check the accuracy of your odometer by using mile markers on the freeway. The check should cover at least ten miles to compensate for any errors in marker locations.
You can check the accuracy of your odometer by using mile markers on the freeway. The check should cover at least ten miles to compensate for any errors in marker locations.