Best of Deals Car Reviews Repair Shops Cars A-Z Radio Show

Ethanol in gasoline

At the end of August my 98 Toyota Corolla experienced a drop in gas mileage from 26 to 22. It happened at the time of a tune up and brake job. (See a previous question I asked if you like)

Since then I’ve had both the work done double checked to be sure the original work was not the cause, but I’m still left with the problem.

Last week I heard a federal bill recently went into effect that allows gasoline distributors to add ethanol to gasoline and they don’t have to label it anymore.

Is this true? Does anyone know about this?

I have never bought ethanol gas and always go to P66 or BP. It could explain the MPG drop.

Don’t think so. Here is an interesting study of various levels of ethanol and the effect on the three cars under study:

Do you have a DTC code for a check engine light?

Interesting report. I really with they had also included a turbo-charged 4 cylinder model, and other higher compression models in the mix to see they respond.

With a 10% mix I wouldn’t expect it to drop that much.

But, you may want to change out the fuel filter, as it could be getting clogged up from the effects of the alcohol on the gas tank (cleaning). If the engine gets starved intermittently for fuel because of this, the ECU can adjust by putting in more fuel overall, possibly causing what you are seeing.

Either way, a filter is cheep and needs to be changed every so often anyhow (see your owners manual).

In some areas they are required to add some alcohol in the winter and I don’t believe they are required to post that.

While it is true that alcohol will lower mileage, I don’t believe it would make that much of a difference.

A 15% drop is too much. It could be a combination of 10% ethanol and other things. What is your tire pressure? It should be the Toyota recommended level. It should be on a plaque inside the driver’s door (or trunk).

On my car you have to have a special piece of equipment to read the code causing the light to come on. I do not have that so I don’t know what code it has.

Since the Seafoam (re:earlier question) was added to the car the light has come on and gone off by itself 3 times. That is annoying because by the time I can get someone to look at it the light goes off. One mechanic suggested I run another batch of Seafoam through the car.

I have thought about changing the fuel filter. Done it on older ‘simpler’ cars. Don’t have a clue on this one. What is ECU?

I regularly check the tire pressure - no issues there.

Do you live in an area where the weather has suddenly gone chilly? Where I am, in NH, we can suddenly feel winter coming on and that adversely affects gas mileage.

It’s due for the fuel filter to be changed so I’m going to have that done. The check engine light is on again so hopefully it will be on when I have that done so they can check it.

A friend told me he had a drop in gas mileage after sea foam and the fuel regulator valve screen was clogged up. I’ll have that checked too.