Bad gas mileage?

2003 LINCOLN TOWN CAR
139,000 MILES • 4.6L • V8 • 2WD • AUTOMATIC
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THEPLUXOH
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I'm stuck on if I'm getting bad gas mileage. Google says 17/25, I'm getting 18 all day every day. I've done a tune up, but gas mileage has not changed. I'm going to calculate it on an app and see if my dash is wrong. Here's a list of things I've changed for reasons I suspected were OEM, and what could possibly cause bad gas mileage.

Spark Plugs (Iridium)
Fuel Filter
Coils
Synthetic Oil Change
Coolant Temp Sensor
Thermostat
Rear Diff Fluid
Brand New Tires

I don't know if my transmission fluid has ever been changed. I don't see a record of it. Not sure if my fluid is bad, but it looks like good fluid.
Jan 13, 2022 at 12:30 PM
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SQM
  • CERTIFIED EXPERT
  • 6,383 POSTS
Hello,

The EPA mileage rating is 17 city and 25 highway as you know.
However realistic mileage for these cars are often 14-15 MPG on typical city and 19-22 on highway. But that will also depend on the driving condition, driving style, outside temperature, terrain etc.

So, you are getting the 18 MPG is actually reasonable.

Another thing to keep in mind that those EPA mileage ratings are for new cars in ideal condition.
As the vehicle accumulates miles the internals of an engine and drivetrain will worn, and they will lose some of the efficiency.

From the list of items you mentioned, you have done all the right things and taken the right steps.

Changing the transmission fluid can be done, however it will not improve the fuel mileage.

Please let me know if you have any questions.
Thank you.
Jan 13, 2022 at 12:46 PM