Do Wider Spark Plugs Gaps Increase Gas Mileage

Posted in Ignition Systems
  • Does increasing spark plug gap above factory specs increase gas mileage? If so, what amount beyond factory on average gets the best improvement in mileage?

    There are 3 Answers for "Do Wider Spark Plugs Gaps Increase Gas Mileage"

    1. itsthewill says:

      no, doesn’t help

    2. gremlingts says:

      no, not wider gaps necessarily , they are just there for high energy systems versus the older points-based system, which had lower voltage coils and couldn’t jump the bigger gap.

      If you get a MSD unit ( Multiple Spark discharge ), you can have your plugs fire 2-3 times each stroke, which will help reduce mis-fires, and WILL improve gas mileage a little bit. They can be costly, and might require computer chip reprogramming in your car/truck, but it is one of the few spark changers which WILL help a little.

      Another change is positioning the spark plug so that the finger which extends over the center electrode is not blocking the intake valve discharge. I don’t know how it is possible to line them all up, depending on the threads, but hot rodders have marked them and then shimmed them so that the rear of the side finger won’t block the air and gas flow from the intake valve, which gives it a clear shot at the spark. A VERY picky point, but I suppose it could affect gas mileage on a few cylinders that way. And so minor, but when you need 1-2 extra HP out of a 1,000 HP mega-motor, I guess any small advantage is STILL an advantage.

      - The Gremlin Guy -

    3. mdk68gto says:

      a gap that is wider than spec can lead to a misfire or premature failure in the ignition system.