Why isn't my mpg increasing??
 

So, about a week ago, I replaced the spark plugs on my truck, and on my next fill up, the gas milage didn't change at all! It stayed the same. I used the Campion Double Platinum plugs, and it seems to be running fine. any ideas? I'm stuck at 13 miles per gallon. Thanks guys.

One tank of gas isn't enough to see if the new plugs have made a difference. Go through a few tanks and see what happens. Also, 13 mpg in a 2nd Gen 4x4 isn't too bad, really.

13s about average. So your truck is probably running just fine.

That's about the average MPG around here. I didn't have any luck with the dbl plat. plugs, I went back to standard copper champion plugs.

Plugs, plug wires, age/condition of the in-tank filter screen, injector rail condition (is it plugged with debris?), injector inlets (are they clean?), cap and rotor bug age/condition.

Plus, you're driving a 4X4 -- not the most efficient vehicle on the road.

Unless there was something wrong with the plugs you changed, simply replacing them wouldn't show much, if any, change in your mileage/performance. The biggest gain in using better plugs is in situations where cheap plugs fail and in reliability. Towing, off-roading and other situations that test your engine's limits all benefit from better plugs, but don't expect to see actual measurable gains.

Also, did you change anything else? When was the last time your plug wires, your distributor cap, or your distributor rotor was changed?

Don't expect dramatic increases. By replacing all of the above, I netted only about 0.5 MPG more or so.

Good job guys!1 I think we hit the nail on the head!! You can't polish a turd!

i dont want to hear it.....haha...im averaging 9.5 mpg....almost 10 on a good day and ive replaced all that!!

Actually, when I put plats on my truck the gas mileage went down. Went to the copper autolites and that seemed to improve mileage a little bit, but that was during the whole tear it out and replace it phase to get the mileage up. Just filled up today and netted 15MPG (75% highway)