I wanted bosch 4s in my truck but instead stupid firestone put in champion copper plugs and i noticed i wasnt getting 60 miles anymore before the gas gauge moved. I check and noticed that all the plugs were .015 instead of the .040. Any chance gapping them would get me back my mileage?

 

just out of curiousity what were so special about the plugs u wanted versus the ones installed?

 

supposedly bosch 4 would get the best mileage and horsepower except for the high dollar iridium ones.

 

+4 = gimick. You want a big spark to ignite the mixture. I'd stick with copper and a single spark. Plus they're easier to gap. But yeah, gap those suckers. The bigger the gap the higher voltage required to bridge it, might as well get the biggest spark your ignition system was designed to put out.

 

I agree...for the most part the +2 and +4 that bosch make is waste of money. As far as I know the voltage is the same regardless of if you have one spark or 4. I have the iridium plugs in my car only because that is what is recommended but I would say the gap issue that you have is a big deal. Plugs come pregapped for a reason and the manufacturer doesn't give you the specs of the gap just for $hits and giggles. I would say that may be your problem. Good luck, hope that fixes it.

 

I gapped em and it seems to be smoother just hoping its fixed lol. Cause when i first start it up exhaust sorta has that nice glug glug sound then smooths out just hope that normal lol.

 

.040 stock gap, .054 w/MSD 6-AL amp.