Five Things You May Not Know About Flex-Fuel Engines
1. They’re pretty much the same as a normal engines. Aside from a different set of spark plugs, injectors that can pulse more fuel, and a more corrosion resistant fuel system, flex-fuel engines are essentially identical to regular old gasoline engines. To see what “essentially” means, read more below.
2. When you run E85, your fuel economy drops 20-30%. This is because ethanol contains less chemical energy than gasoline. Put another way, ethanol burns cooler than gas, so it takes more than one gallon of ethanol to do the same amount of traveling that you can do on one gallon of gas. Provided that E-85 is at least 20-30% cheaper than gas, it’s a push. Otherwise, running E-85 might be costing you money.
3. E-85 absorbs water like crazy. That’s not a scientific observation of course, but it’s a good description. Check this out:
ethanol is hygroscopic by nature. This means that it immediately soaks up water both in liquid form and as condensation right from the atmosphere. Hence ethanol cannot be transported through petrol pipelines. Worse yet is that any prolonged exposure to the air itself can begin to dilute ethanol (due to water absorption)
This explanation from the Energy Refuge blog is specifically about the transportation problems associated with pure ethanol, but all of the above information applies to E-85 fuel.
E-85 will absorb whatever water is nearby, and given enough time it will dilute itself enough to cause combustion problems. While is is very rare, it *is* technically possible. The downside to water absorption is that burning “wet” E-85 can cause excessive amounts of formic acid to be created during combustion. Formic acid can eat engines, which means that…
4. A flex fuel engine’s parts are treated to resist formic acid. Because the risk of water contamination in an E-85 engine are fairly high, automakers use a special nitride coating on all the internal engine parts that may be exposed. This prevents excessive wear if a particularly watery batch of E85 is burned.
5. Manufacturers may recommend more frequent oil changes when running E-85. If you live in an area where E-85 is readily available and cost effective, you may be using it every day. If so, your local dealership may suggest you change your oil more frequently. Their reason? Acids formed during ethanol combustion can reduce the lubrication properties of motor oil, therefore requiring more frequent changes.
Unfortunately, this is pure hogwash. Most modern oils contain more than enough detergents to nuetralize the acids that E-85 may produce without compromising lubrication, so they do not need to be changed any earlier than normal. Read more about why more frequent oil changes are not needed if you’re running E-85 if you’d like to find out more.
6. (Bonus!) When your manufacturer built your flex-fuel vehicle, they got a special fuel economy credit from the government. In a system that’s both unseemly and absurd, auto manufacturers are given fuel economy “credits” for building flex-fuel vehicles even though these vehicles don’t get better fuel economy. The TerraPass blog has a great post that explains how a Chevy Suburban was credited with a 30mpg fuel economy rating despite actually getting 12-16 mpg – check it out.
Finally, for you Tundra owners out there, a flex-fuel engine is not compatible with the TRD Supercharger.
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