Kitulu Posted August 6, 2013 Report Share Posted August 6, 2013 Prior to changing my sparkplugs, I was getting between 15-16 mpg in city driving, and 23-24 on the highway (@75-80mph) After changing my plugs two weeks ago, my city milage is now hovering around 13 mpg. I used NGK platinum plugs, gapped at .054, and changed the air filter and PCV valve while I was there. The old plugs were showing a gap of .080, give or take. Why has my milage gotten worse? Quote Link to comment Share on other sites More sharing options...
WWWPerfA_ZN0W Posted August 6, 2013 Report Share Posted August 6, 2013 NGK Platinum 5019 plugs? Motorcraft EV257 non-heated PCV Valve? If anything, new parts should have increased your mpg's. Maybe you have a weak coil or improperly seated wiring boots? Is the engine running smoothly? If you disconnected the battery, could be the PCM's learning period also. Quote Link to comment Share on other sites More sharing options...
Kitulu Posted August 6, 2013 Author Report Share Posted August 6, 2013 I did not disconnect the battery, and I double checked the boots on reinstallation. The engine is running fine. After reading the manual, it states that the MPG meter should be reset while travelling at a constant speed for three minutes. I had reset it just prior to going home from the gas station. I reset it today on the way to work and it is reading 18 MPG now. Quote Link to comment Share on other sites More sharing options...
WWWPerfA_ZN0W Posted August 7, 2013 Report Share Posted August 7, 2013 Chalk it up to Ford's weirdness with MPG measurements? Hopefully you will get a better feel for it by the next fillup. Quote Link to comment Share on other sites More sharing options...
Ironpeddler Posted August 27, 2013 Report Share Posted August 27, 2013 Start tracking your mileage using the 'Fuelly' app on your cell phone...that will take the guess work out of it. Quote Link to comment Share on other sites More sharing options...
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