E85 Gas in a Non Flex Fuel Car

Two weeks ago, my boyfriend offered to pump gas for me, and after he put the pump back into the gas slot, I noticed he filled my tank with E85 fuel.

I drive a 2007 Ford Taurus SEL that is NOT a Flex Fuel car.

I immediately called my local Ford dealer’s service center to ask if I can drive with a full tank. He said it should be fine, just fill it up with regular gasoline when I get a chance.

The car ran fine. The next day, when we were driving back from our trip, the Check Engine Light came on.

I did some online research, and read that this commonly happens after E85 fuel is put into a non Flex Fuel car, since the O2 sensor is affected by the burn off of the E85 fuel.

Since this has happened, I’ve filled up my tank twice with regular gasoline, but the Check Engine Light is still on. Will the light eventually go off? Should I be more worried about this? The car seems to be running fine - the engine isn’t rough or anything like that.


The light should go off after the right number of start/stop cycles with good gas in the tank. Give it a few more fill-ups before worrying about it.

The “check engine” light may or may not go away on its own. It depends on the problem.

E85 can destroy rubber parts that can stand up to normal gas or E10. If this is what is causing your “check engine” light to come on, the problem won’t just go away. If it doesn’t go away in the next few days, you will need to get the codes read from the computer, which you can usually get for free at many auto parts stores. Post those codes here and we will help you figure out what is wrong.

I stopped at Auto Zone after work (thanks for the tip!). The code was PO174 - system too lean. The guy reset the computer so the light is off. Looks like I should be all set.

Well, it can come back again. Any chance you can siphon the fuel out of the tank? Maybe your boyfriend should help!

I’ve let the tank go down pretty close to empty, so I could get as full of a tank of regular gasoline as possible (I’ve gone through approx. 2 tanks of regular). I’m sure the E85 fuel has made its way through the system. I’ll definitely keep tabs on the dash to see if the light turns on again.