spark plug gap and bad gas mileage [Archive] - Forum


View Full Version : spark plug gap and bad gas mileage

06-11-2007, 09:10 PM
ive been having terrible gas mileage(15 mpg) for some time now and after working on my cousin truck this weekend and tuning it up, i remember that i did not gap my plugs when i changed them last year (stock ac delco)

would this be causing part of my bad gas mileage??

06-11-2007, 09:17 PM
Ive been noticing the same, but Im using AC delco iradiums which are supposed to be gapped. I was wondering if its the full exhaust and the Cold air Intake causing the bad milage, Im also using 89 octane.

06-11-2007, 09:23 PM
well i have an intake and a milzy pcm so im running 91 or 93 octane...the only real places i drive the car are to work with is all city roads(not even 6 miles each way) and sometimes to the club which is a mix of both(15 miles max each way)

06-12-2007, 01:08 PM

06-12-2007, 01:36 PM
When was the last time you changed the fuel filter?? Also how many miles are on the car? I changed my fuel filter and got a little bit better MPG (around 17) then changed the o2 sensor and got it back up to around 20-21.

06-12-2007, 03:40 PM
u cannot accurately measure MPG in that short a span and in stop and go traffic and also at times when u start and kill you engine alot in one day. it takes alot of gas to get the engine started i have seen and that is part of the problem. the plugs should be gapped, but always check them to make sure. also try to run with the least amount of weight in the car as possible and make sure your tires are properly inflated, plus remember, when u run the AC and alot of high powered accessories like stereos and such, then ull put more load on the engine and ull use more gas.

06-12-2007, 03:48 PM
what do you mean by gapped plugs?

06-12-2007, 03:50 PM
the gap between the electrode and the groud strap, usually measure in thousandth of an inch or millimeters

06-13-2007, 09:21 AM
So what does it mean by gapping your plugs?

06-13-2007, 09:31 AM
So what does it mean by gapping your plugs?

you have to adjust the gap on the plugs to be the correct size for your application.. this is called "gapping"