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why did the car miles per tank full, on my 2004 taurusSE has gone, from 310 miles to 256 miles?

Please describe the driving you were doing before and after that happened; length of trip, traffic, weather, etc. Have you moved or changed jobs?

Also condition of your Taurus now and then, any repairs or adjustments made?

When we get a question like that the poster usually tells us why he thinks he gets worse mileage in Boston city traffic than in Texas, for example. Or a switch from gas with no ethanol to E85, wich is 15% ethanol.

I could list a very large number of reasons why gas mileage goes down, but I won’t list any until you give us more information.

Let me guess – you were driving up hill instead of down hill?


I am still in the same area doing basically the same type of driving as from purchase date. Since the last 2 years it has gradually being going down. First it was 290 something, then 280 something, then 270 soemthing and so on and on. I did not register the changes as to whether they were occuring every 3 or 6 months or so. Other than gas filter, air filter, oil changes, fluids, wiper blades, tire rotation and balancing, in other words PM, that is all that has been done to it. Other than buying a new battery and four tires, there has been no repairs done to it. It has not been involved in any accidents, fender benders or the likes. It has great pick up and everything is working fine, there are not lights or whistle coming on.

“Other than gas filter, air filter, oil changes, fluids, wiper blades, tire rotation and balancing, in other words PM, that is all that has been done to it.”

What about spark plugs?
If the plugs are the originals from 2004, it would not be surprising that your gas mileage has continued to worsen.

there are not hills in Florida unless you drive into a gabage dump then you will encounter a hill

they were changed at 50,000 miles

Note: measuring fuel usage by the tank is not very accurate, You really should measure it by dividing the number of miles by the number of gallons.

Math is math and numbers cannot 2 plus 2 is 4, the same as 3 plus 1 is 4. A tank full is 16 gallons, at 310 miles to a tank full it is 19.375 miles per gallon, at 256 miles to a tank full it is 16 miles per gallon. The fact that I was able to drive 310 miles per tank full does not change just because I am giving you a miles per gallon rather than miles per tank full, since with a tank full I can only reach 256 miles from where I filled.

Are you actually putting 16 gallons exactly into the car? And when you fill up again do you measure the gallons and compare it with the miles driven?

Elementary questions, but the tank capacity listed in the manual has very little to do with how much goes in when you gas up.

I can only go by what the pump reads. Have not had this issue before and the pump reading was accurate and I know how often I need to fill now versus in the past. Other than these common sense indicators I do not have any other way to measure it, but I do know that there is a problem. I just wish someone will shed a light on the cause before I take it to a mechanic that will make me go through the same I am going thru on this post

Fuel economy can drop with different tires and if the tire pressure is low. Make sure the tires are inflated using the placard on your vehicle. I run 32 psi because it gives the best tire wear and fuel economy.

Cruise control set to a higher speed on the highway, headwind vs tailwind, incomplete gas fillup, aggressive driving, ethanol in the gas, luggage rack, water standing on the road from a hard downpour all can change your fuel economy.
Gas dispensing pumps aren’t always right on the money either. Try buying your gas somewhere else and see if you get different fuel economy.

The only way to get an accurate MPG figure is to use the EXACT SAME PUMP at the SAME station, and stop filling at the FIRST CLICK.

You need several tanks of gas and take an average. I have experienced some pumps that click off early, others very late.

If you tanked normal gas before and then switched to gas with ethanol, you mileage will drop significantly as well.

P.S. What the pump reads is MEANINGLESS, unless you do exactly as described above. One gentleman I know claimed 32 mpg on his Dodge Hemi truck. He hit a pump that shut off early.

cruise control is not set unless is a long trip of 12 hours and above. One driver, same location aince day of purchase.
This car has always done a lot better on highway driving, at high speeds.
Rarely if ever do I purchase my gas at the sme place, do not have loyalty to corporate america.

Is there a check engine/service engine light on?

Even if there isn’t I would ask someone to check out your EGR system - especially the EGR feeds to the DPFE sensor and the DPFE sensor itself. These systems are problematic and can mess with fuel economy.

Could be time to replace the thermostat.

…and have the coolant temp sensor checked.

wow, first person that seems to make sense. That were my thoughts that it had to do something with the sensors I just didn’y know which ones

It makes sense, those were my thoughts that it had to do something with the sensors I just didn’y know which ones