View Full Version : 10% alcohol fuel...bad news

06-04-04, 08:32 PM
Hi, new to the group. Any info or opinions on the use of 10% ethonol in our fuel? My '99 Deville and '02 GMC Sierra Denali don't seem to like it. The mpg went down about 1 1/2 and I get noticably poorer performance. I have read that it's not good for most engines and very bad for rubber fuel system parts. Any links?

06-04-04, 08:49 PM
I have lived in the 5 county Chicago metro area all my life and have used 10% ethanol since it was mandated in this area. I can't speak for milage as I have never done a comparison but I have never had any problems either. Perhaps ther may have been some problems when it first was introduced but now fuel systems are designed for it.

El Dobro
06-04-04, 10:18 PM
If you check your owner's manuals, all the fuel recommendations for your vehicles are in there. It tells you what you can and cannot use.

06-04-04, 10:58 PM
Hi, new to the group. Any info or opinions on the use of 10% ethonol in our fuel? My '99 Deville and '02 GMC Sierra Denali don't seem to like it. The mpg went down about 1 1/2 and I get noticably poorer performance. I have read that it's not good for most engines and very bad for rubber fuel system parts. Any links?

Perfectly normal.

It takes twice as much alcohol (compared to gasoline) by volume to achieve the same chemically correct air/fuel ratio. So...if you use fuel that is 10 percent alcohol it will run require about 5 percent more fuel to drive the same distance....something that they "forgot" to tell you about the wonders of alcohol. So your loss in fuel economy is pretty darned close to what one would expect with 10% alcohol.

Running pure alcohol it takes exactly twice as much fuel to drive the same distance compared to gasoline...so, if you were (theoretically) running pure alcohol your fuel economy would be cut in half based purely on the volume of the fuel pumped into the car.

The alcohol fuel really shouldn't hurt anything as the system is designed to tolerate it...but 10% is the absolute maximum that the system should see and it is at the limit of what the computer can compensate for so that is why you are starting to see some driveability issues...

06-04-04, 11:35 PM
Reformulated gasoline (RFG) and alcohol-blended fuels have been around for a long time. You might also hear RFG called oxygenated gasoline. Engine manufacturers design engines around the need for RFG and almost nobody advises against using it anymore. There has always been a lot of confusion and misinformation about 10% ethanol gasoline, reformulated gasoline, MTBE, methanol, etc., but the essential message to remember is this:

Almost all cars manufactured after about 1985 were designed with MTBE and ethanol blended gasoline in mind. Alcohol blends will decrease your mileage a small amount, typically in the neighborhood of 2 to 5 percent, but the performance change is rarely ever noticed. The decreased mileage is not the result of a poor gasoline. If the octane rating you put in the tank matches what the manufacturer recommends, that's all you need to be concerned about in new vehicles.

The requirement for reformulated gasoline is an EPA mandate that kicked in on June 1 and runs through I believe the end of August or September. The difference is it will not vaporize as quickly, which reduces smog during summer months. Refineries typically start producing RFG in late May, and it's possible to get a tank full of RFG a little before June 1. Most people never notice the difference. It's not going to hurt your engine at all. Auto manufacturers were heavily involved in the specification for RFG, and your newer vehicles definitely were made with RFG in mind.

So yes, gas mileage on fuel-injected vehicles will drop a slight amount and it is possible to notice a slight performance drop, but I don't think you should worry about it. If you want the performance and mileage back, you'll have to go to an area where RFG is not required or they don't use ethanol-blended fuels. I suspect you'll have a hard time finding those. Your owner's manuals should have further information. Ask your usual gas stations if they can give you any information about the contents of their normal and RFG fuels and compare that info with your manual.

Reformulated gas plays a vital role in reduction of smog, so I don't mind the minor performance change. Just make sure your air filters, PCV valves, fuel filter, and O2 sensors are all in good shape, injectors aren't fouled, and the engines are tuned up properly. That's the best way to get the most mileage and performance out of your vehicles. RFG and ethanol blends are here to stay.

Hope that helps. Happy breathing! :D

06-05-04, 08:22 AM
IS the alcohol blend less costly to buy. Do not have at any gas station around here.
I wish I had quadsteering for my 03 ext cab!

06-08-04, 01:09 AM
Nope, it's just as much, if not more expensive by about $.12/gal as it is around here. I was always told that the 10% blend was bad for your car, but I can't personally tell you if it's true or not. One would assume 100% pure gas would be best for reliability.

06-08-04, 12:27 PM
Here's even more information about gasoline than you ever wanted to know... :bighead:

Yes, ethanol is more expensive than gasoline, so 10% ethanol blends will usually cost a little more than non-ethanol gasoline products. There is no such thing as 100% pure gasoline because there are additives in all of them to help keep injectors clean, reduce valve deposits, etc. Gasoline is not a single hydrocarbon chain, meaning it consists of various amounts of lots of layers of the crude oil refinement process. The vast majority sits in one area of the distillation stack, but, like mineral motor oil, there are components heavier (naptha, etc.) and lighter (xylene, benzene, etc.) than the average. Ratios of the various components vary from tank to tank in most cases due to minor imperfections in the blending processes, though the blending process is far more accurate now than it was even 5 to 10 years ago. Certainly there will be differences in the various components between refineries, and the oil companies use different additives in different ratios, etc. That's why the phrase "100% pure gasoline" refers to a product that simply does not exist.

The lighter components such as xylene and benzene are known as aromatics and were present in far higher levels in the 80's and prior. Because their vaporization rate is far higher than the rest of gasoline components, they tended to cause a condition known as "vapor lock." On hot days and when trying to restart a hot engine especially, vapor lock could occur when the aromatics vaporized in the fuel lines and prevented sufficient liquid gasoline from reaching the carburetor. Most of the aromatics are known cancer-causing agents, especially benzene, and EPA mandates have forced manufacturers to reduce the level of aromatics by big margins. Along with that came the almost total elimination of the vapor lock problem. When aromatics levels were still very high, it was still called gasoline, which again leads to the conclusion that there is no 100% pure gasoline. Ethanol/gasoline blends were introduced around the same time that aromatics levels were very high, which led a lot of people to the conclusion that it was the alcohol content of gasoline that caused the problems. That simply was not the case, but that perception exists to this day.

Auto manufacturers have been developing engines and fuel system components with alcohol-blended fuels in mind for a long time now. The main thing that comes to mind when someone says "alcohol fuels are bad for your engine" is methanol. Methanol is a completely different beast from ethanol. Some auto manufacturers recommend against methanol, others allow for a 3% or 5% blend as long as there are also components that counteract the negative effects of methanol. Methanol can deteriorate some rubber- and plastic-based tubing, o-rings, and gaskets. Most auto manufacturers have been using materials that are not affected by methanol for a long time, but they still recommend against using it for reasons that are unknown to me. (anyone care to comment here?) Another additive that received a great deal of "bad press" in years gone by was MTBE, or methyl tertiary butyl ether. MTBE is not methanol and does not contain methanol, and is not an alcohol but an ether. It is used to increase octane without increasing pollution-causing components of petroleum. Two other similar additives are ETBE and TAME, but I don't have any information about them other than the auto manufacturers seem to be ignoring them mostly because their pros and cons are almost identical to those of MTBE and they already allow MTBE to be used.

So as far as which gasoline to use, it all boils down to this: (pun partially intended)

Follow the recommendations set forth in the owner's manual of your vehicles. If it says to use 87 octane fuel and that ethanol at 10%, methanol at 5%, MTBE, and reformulated gasoline (RFG) are okay, then that's the bottom line. Using 89 or 93 octane gasoline will not gain you anything to speak of, especially not for the difference in price. If you use 87 octane gasoline and experience knock problems, get the car checked out by a qualified mechanic. Something is causing the engine to require higher octane gasoline and may indicate other problems.

Hope that answers your questions... Happy refueling! :coolgleam

Michael Cowden