I have a 1998 Ford Explorer 4.0 liter sport 2x4 with 131,000 miles on it. On average I was getting about 280-300 miles to the tank (15 gal). Recently I noticed that my gas mileage has fallen drastically. [260 miles to the tank, then 241 miles]. Pretty bad even for winter. So I checked all the usual stuff. Changed the air filter, changed the plugs and wires, and changed the oil. The mechanic plugged the truck into the computer and said that all the sensors are reading good values (with special interest in the O2 sensors). After that I got 270 miles to the tank. Then I got a brake job and had the trans fluid exchanged and now I got 230 miles to the tank. The mileage has never fluctuated like this. I have no idea where 4-5 gallons is going. There are no puddles under the truck. Does any one have any experience or tips on what I could look in to? Has this happened to any one else? Anything would be a great help. I am out of ideas.
Thanks,
Fritz

 

might be additives, colder states add to the fuel.
u change the oxygen sensor??

 

I don't know, 15% fluctuation seems to be a bit much for cold weather affect. I used to get 19.3 mpg, now I get 14.5 mpg. My mechanic thinks 8% would be about right. The last tank I burned 15 gallons, and travelled 218 miles. My mechanic checked the oxygen sensors and said they are reading appropriate values.

 

Something that I just noticed on Friday, while filling my truck, was a sign on the fuel pump that said "This fuel may contain up to 15% ethenonal. While I am a proponenet of any way to lessen our dependence on oil imports, I would like some advance notice of this being added to my fuel, instead of a small sign on the pump. It makes for a cleaner burn, but also lowers the reeed vaor pressure of fuel, thus giving it less power as it burns. This reduces fuel economy.