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04 explorer 4.0 l now 12 mpg city was 16

11-04-2011, 05:31 PM
what's causing this reduced mpg since I started driving it at 44k mi, now at 58k mi? All original parts, possibly except for air filter. Passes smog great. What should I have changed 1st, 2nd, etc and recheck mileage? Driver and habits same during this time. Thanks.

11-04-2011, 07:59 PM
Oil and filter, fuel filter, air filter. Tire pressure and signs of wear that do not look normal. Also remember that new gas has ethanol in it so you get worse MPG then if you had pure gas.

11-04-2011, 10:54 PM
The air filter wouldn't happen to be an aftermarket oiled filter, would it, such as a K&N or Spectre? If so, the oil may have coated the MAF sensor causing the decreased fuel economy. You can clean the MAF sensor with MAF sensor cleaner or electrical parts cleaner, no need to replace the MAF is it's just coated in oil. It is easier to clean though if you have the security Torx bit and remove the sensor element from the housing.

Of course if you don't know the maintenance history it wouldn't hurt to replace the spark plugs as well. I don't recall if the 2004 V6 uses CoP or if it has spark plug wires. If it has plug wires, replace them as well.


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