Will changing away from 10% Ethanol change performance noticably?

I have a '98 Suzuki Sidekick, and my EGR sensor code kept coming on, but the mechanics said there was nothing wrong with it. I live in Nebraska, so we subsidize 10% ethanol fuels, and I always used that. But it was suggested that I switch to the regular; I did and the code hasn’t come on since.

But I just noticed that when I take my foot off the gas, the car still maintains speed for a while, almost a whole block, and it even did it to some extent up a hill. The effect is much different than it used to be. (I really noticed it by thinking something was wrong with my brakes because the same pressure on the brakes as before wouldn’t stop the vehicle as fast.)

So the question is, is that just some benefit of not using ethanol, or is there an actual problem?


Carina from Lincoln

The 10% blend will probably reduce your fuel mileage and you might notice a little less power with it, but other than that there should be no noticeable difference in the performance of your car-- it sounds like you have a problem with your EGR valve that you should be addressing. Judging by the symptom of the car not slowing down, it sounds like it might have failed in such a way that it’s leaking vacuum and causing your engine to race. This is definitely not normal and you should get it checked out ASAP.

Maany drivers switch back and forth, buying whatever is available. They do not notice any difference in their car’s performance, certainly not the symptoms you mentioned.

Try this: bring your car up to speed and shift into neutral. The rpms should quickly drop to what is normal for idle. If not, consider Jack’s suggestion of an EGR fault, or maybe a problem with the idle air control (IAC) motor.

Reformulated gasoline has another advantage: There is not MTBE in the gas to leach into soil in the event of an underground tank leak. Most large metro areas are not allowed to sell MTBE treated gasoline. The closest areas to you would be St. Louis or Chicago.

The symptom you describe is the result of a problem, not the ethanol. The only difference between 10% ethanol and straight petrol is that the ethanol has slightly less energy, so some drivers notice a slight powering of mileage and power.

I too vote for the IAC as the prime candidate. A faulty Throttle Position Sensor would be right up there as a candidate also.

Slightly off topic yet close enough to ask. What retail service stations sell only straight gasoline—no ethanol?
At one time I know Marathon said they did, but I have none in this area of the southwest.

Here most gas stations sell three kinds at each pump: 10% ethanol, regular (no ethanol), and premium. Like I said, I live in Nebraska, so our setup might have something to do with supporting corn-based ethanol. Here, regular is about 10-15 cents more expensive than 10% ethanol, but people say 10% ethanol gets slightly worse mileage, so I figure it works out about the same, but with 10% ethanol we are supporting the Nebraska farmers most likely. That’s a whole other debate, though. Or do you mean even “regular” gas has a little (1%-2%) ethanol added? That, I don’t know.

Thanks for the suggestion! This is probably a silly question, but do you mean with the foot off the gas? And if so, if the rpms do drop, could it still be the IAC motor?

OK, thanks! I made an appointment for next week. Interesting, though, that most of the comments say it is definitely a problem, but they suggest different problems.

It looks more and more as if you have an IAC that is not doing its job correctly. In such cases the check engine light typically does not come on.

A new IAC motor costs in the range of $50 and is usually simple to replace. Mention your test to a mechanic and see if he agrees or if he has another theory. But don’t blame the fuel.

All gasoline’s have an additive that controls the octane level. In most of the US (by population), it is exclusively by ethanol. In most of the US (geographically) it is by either ethanol or MTBE. Almost everywhere you drive, gasoline with MTBE is available. Unless you live in a large metropolitan populated area. But even Denver is not big enough to require ethanol only.

Almost everywhere you drive, gasoline with MTBE is available.

I just googled mtbe ban and looked at the DOE EIA list. 17 states (including NY, CA, and OH) have banned or severely restricted MTBE.

Ethanol may have some octane-boosting properties, but the main purpose (besides buying votes in Iowa) is as an oxygenator to reduce emissions. For this it is replacing MTBE, which has a nasty habit of polluting groundwater.