Thread: gas mileage

Every weak I drive 170 miles
Seattle to Portland.

170 = half a tank
Full tank is 340
Divided by 18 capacity.
Is 18.8

I need to figure out how to change the plugs maybe it would help.

Are you just going by the gauge ? That is very inaccurate.
Fill it up until the pump clicks off, no more.
Drive it down below 1/4 , fill up again.
That will give you the actual gallons used.