Recent drop in mileage

I have a 2006 Lincoln Town Car that has been getting at least 20 miles per gallon. Two weeks ago the oil was changed and I can’t say what the mileage was right before that. Yesterday I noticed that the mileage, according to the dashboard readout, is slightly less than ten mpg.

Maintenance other than oil changes has been minimal. This has ben a great car and I don’t want to have to trade it in.

Depending on who you had change the oil, I would be looking for a problem with the O2 sensor, coolant sensor, air sensor etc. Did they also check things like the air filter and could have disconnected the air sensor? Someone is going to have to take a look, either you, them, or have a diagnostic done for $100 to see what the sensors are reading.

“Maintenance other than oil changes has been minimal”

I think that you answered your own question.

First, make sure that the tires are inflated properly, and then bring the car’s maintenance–including spark plugs, air filter, and fuel filter–up to date, and see what your gas mileage average is like over the course of 3 tankfuls. If the gas mileage is still lower than previously, then you have to look elsewhere for the cause, but basic maintenance is always the first thing that needs to be taken care of.

Maintenance other than oil changes has been minimal.


Cutting back on maintenance is the most expensive way of saving money I know. I would expect better than 20 mpg for that car anyway.

OK one possible for the other side. Those dashboard mileage meters are never real accurate and often very inaccurate. Measure mileage the old fashion way (miles divided by gallons) at least three tanks in a row and compare that with what the readout is saying.

Here’s my theory.

I’ll bet the same fancy computer thing that tells you your mileage also comes on to tell you when it’s time for an oil change. I’ll bet that while the guys changing the oil were trying to figure out how to reset the oil change indicator, they accidentally reset the mileage computer. If you’d in the past done a lot of highway driving that brought the average up, but you’ve only done urban driving in the last two weeks, that could easily explain the drop in indicated mileage.

GreasyJack may be right! I am the well know little old lady that only drives to church on Sunday, the grocery store or Walmart on Wednesdays, and wears red tennis shoes. Just kidding! My tennis shoes wore out a couple of years ago. I rarely drive more than a couple of miles at a time. Today I drove to a town about fourty five miles from home, and by the time I got back the mileage was up to 22.5 mpg.
I AM going to get a tune up though as soon as I get my Social Security check.

I would suggest checking the MPG manually using trip meter reset at next full fillup. At the next fillup to near empty divide miles on trip meter by gallons to fill and see if MPG correlates.

Check back in if the computer reading correlates to your calculated MPG.