Gear up 10% by installing 185 75 14 tire should get you an additional 5 mpg

[Goldironduke]

I installed a new set of Hankook H724 185/75/14.

10% drop in RPM

Mileage went from 50 mpg to 55 mpg with cruise control on in open road.

55 mph/hr 2500 rpm
60 mph/hr 2750 rpm
65 mph/hr 3000 rpm

Engine does not like to pull very well less than 2500 rpm as torque drops off real fast below this point.
I do not believe I could gear it up any higher than this.
Tire size is also maximized

Any thoughts on this idea?

[ahintofpepperjack]

Have you corrected your speedometer for the larger tire size? Your mileage will not be reported correctly unless you do.

[MetroMPG]

Hi Goldironduke.

Do you have a manual transmission or CVT?

Welcome to the forum!

[flotownj]

The computer is calculated for the stock size tires. By changing to a bigger diameter without reprogramming the computer all of your measurements are now wrong. The only thing that is correct is the RPM. The MPG and Miles driven are both off now. They make programmers for almost every truck because guys constantly change the tire sizes but I don't think the make one for the Mirage. Honestly you cant even accurately calculate your MPG anymore at the pump because your odometer is off. You are traveling farther than the car thinks you have.

Generally speaking a bigger diameter tire will increase your fuel economy on the highway but decrease it in the city.

[grsupercity]

You should be able to use your phone for miles driven?

[Tinker1980]

You can calculate the difference in the mileage shown and the mileage driven pretty easy. I had 155-80r12's on my metro, which I replaced with 175-65r14's. The circumference of the stock tire was 68.3 inches. The new tire was 72.1 inches. 6% difference. So you multiply miles shown on the odo by 1.06.

[Goldironduke]

I do not know if there if provisions to calibrate this vehicles speedometer?

Just gps for miles driven.
From fuel fills to the top.

[Goldironduke]

Used gps and fuel fills to the neck.

[Goldironduke]

manual trans

[Goldironduke]

manual