Good point. Here in Idaho, and in other states I'm sure, they have "speedometer check" zones on the freeway. These zones are 5 miles in length and there is signage at every mile to allow you to calibrate your speedometer. It isn't an exact science; the driver has to "eyeball" the exact instant the vehicle reaches a mileage sign against what the odometer is showing.

I have determined that my '93 is reading slightly low; therefore my MPG should be corrected by about 2% higher.

Good luck

10.5 mpg in town, to me, isn't THAT bad. Not for a vehicle with the aerodynamics of a sheet of plywood held against the wind.

I average around 15-16 mpg highway. When I was driving in town mostly, I'd get roughly 200 miles out of a tank, which is roughly around 10 mpg too.

Another thought here is that if you have factory gears and larger tires, your engine is having to take up the difference and is therefore working harder. Not only are you effectively getting a taller gear ratio, you're also adding mass to boot. All that adds up in more stress placed on the engine. The more stress it has, the more fuel it uses up. If you were to re-gear, you might actually gain better gas mileage (even after adjusting for speedometer error).

Richard <img src="/forums/images/graemlins/patriot.gif" alt="" />

I use the Miata web page. http://www.miata.net/garage/tirecalc.html

My 95 with 265's gets 16.8mpg without converting and 18.0 with. <img src="/forums/images/graemlins/cheers.gif" alt="" /> <img src="/forums/images/graemlins/patriot.gif" alt="" /> <img src="/forums/images/graemlins/cheers.gif" alt="" />

well adding the 11% only adds 22 miles and then its only at 10.5 miles per gallon which is freakin terrible. I know the larger tires and heavier wheels and added weight to the suspension with the add a leafs and plus the added weight of the fullsize spare will effect gas milage but sweet jesus that is bad gas milage. I am one of those people that drives a SUV that gets horrible gas milage. Atleast it has seen tha dirt. :lol

Being a former Canuc <img src="/forums/images/graemlins/smile.gif" alt="" />, a couple of other items that are of issue:

"Gallon of gas" Canadian Imperial Gallon = 4.546 Liters
U.S. Gallon = 3.785 Liters
Ref: http://en.wikipedia.org/wiki/Canadian_English "Units of Measurement"

Another issue:

Gas Tank Size: http://www.theallineed.com/math/06011804.htm

One more for thought: http://www.fueleconomy.gov/feg/bymodel/1992_Isuzu_Trooper.shtml

Keep in mind the "Canadian Imperial Gallon vs. U.S. Gallon

YOUR mileage may vary. <img src="/forums/images/graemlins/nana.gif" alt="" /> <img src="/forums/images/graemlins/lol.gif" alt="" />

Van <img src="/forums/images/graemlins/patriot.gif" alt="" /> <img src="/forums/images/graemlins/cheers.gif" alt="" />