Are E3 spark plugs worth the extra money?
Are E3 spark plugs worth the extra money? While E3 claims a 3-5 percent improvement in mileage, Edsall found his dipped from 20.11/19.98 the previous two years to 19.18 with the E3 plugs. The E3 plugs aren't that pricey, so if you do choose to try them it won't cost a lot. Just don't be too disappointed if you don't see much – if any – improvement in mileage. Should I replace stock spark plugs? Spark plugs are somewhat durable components and don't need to be replaced too often, that said, the general recommendation is about every 30,000 to 90,000...