Gas mileage went up about 10% I put them in my ’64 lancia flavia replacing very good champion n3 plugs. I set the car up for a fast idle at 1100rpm and after the plug swap the idle was 1400rpm and the mileage went up about 10%. Karen A., Verified Buyer Spark Plugs 5 2020-01-03T21:40:19+00:00 … Continue reading Gas mileage went up about 10%