Ethanol and affects on older cars?

Question

alright I have a 95 nissan pickup...over the course of this year and the end of last since gas stations 'started' to advertise an up to 15% ethanol mixture, my mpg has dropped by at least three points...The truck is getting old I know that but when i've driven it the same way done the same stuff you get used to the 24 mpg it's gotten...now i'm lucky to get 20 on a fill up. I know ethanol burns worse then gas but lately my check engine light has come on and visits to the local auto zone has turned up nothing. So i'd like opinions and your own car mpgs and ages...not the newer ones cause they are more likely to like mixed gas then the older ones...at least that's my reasoning.

Answer 1

Well, I don't know how much help I can be on the part about your check engine light, but after having just helped to prepare a study on Flex Fuel Vehicles which are capable of using blends of up to 85% ethanol (E85), I can tell you a couple of facts.

Yes even the flex fuel cars get lower gas mileages on the E85 typically it's in the range or 3-8 miles per hour less then if you put gasoline in the same vehicle.  Of course these are cars designed to run on ethanol, but the only major differences between them and the non flex fuel version of the car is the computer that identifies the fuel being used and a few smaller upgrades to protect the vehicle from the possible corrosiveness of the alcohol in the E85.  They are basically designed to be most fuel efficient with gasoline.

So the 15% ethanol could cause you to lose a couple mpg because of it's structure, but none of the studies I read while working on the report indicated anything that showed a pattern of problems in the performance or maintenance of vehicles run on ethanol.  In fact ethanol has a higher octane rating than the equivalent gas so you actually get more horsepower on ethanol especailly as the concentration increases toward E85.

So I guess my conclusion would be that it might very well be causing some lost efficiency, but probably not damaging your vehicle in any way.  It's also helping you to decrease greenhouse gas emissions slightly, so if you are in to helping the environment, I guess lesser gas mileage is the trade-off for improving the earth.  Fortunately the ethanol mixed gas even at 15% should be less in cost than a comperable 100% gas version, so as expensive as fuel is, it could be even higher without the ethanol.