Statement: Why E15 gas can cause engine problems.

The energy density of ethanol is 12.18 megajoule’s per lb. Compare that to the energy density of gasoline which is 40.45 megajoule’s per lb. Based on this one can then understand why you have to use at least 40% more ethanol to produce the same energy than gasoline.

It is then a logical conclusion that once you add Ethanol to gasoline you have to use more of this blend to produce the same amount of power. To add more fuel to a fuel injected engine bigger injectors are required. The same can be achieved by raising the fuel pressure but since most fuel systems are not fitted with an adjustable fuel pressure regulator the only option would be larger injectors.

Let’s say a specific engine needs a 200 cc or 19 lb injector to produce 100 hp to the flywheel on 91 octane with a 10% Ethanol blend. If you now increase the ethanol content to 15% , such as was done with E15, this engine will now need a 210 – 215 cc or 20.5 lb injector to produce the same power and to ensure that the fuel mixtures are correct.

Since the engine is only fitted with 200 cc injectors it becomes clear what and where the problem is going to be. Yes, you are rite …..not enough fuel. For a simpler explanation please see at the very bottom under layman’s terms .

Under cruise injector duty cycles will be higher and O2 trims will be slightly higher but the engine management system will most probably be able to maintain the proper air fuel ratio. It is under wide open throttle or heavy acceleration where the problems are going to happen. Because the injectors are too small to deliver enough fuel at wide open throttle one can expect one of two things or a combination of the two, to happen.

1: To prevent detonation the engine management system will reduce timing to the point where the engine becomes very sluggish and forces the ECU to go into limp mode. Leaving you with just enough power to get to a place of repair.


2: The engine starts to detonate continuously to the point where it starts to melt the piston resulting in engine failure.

Add to this the corrosive nature of Ethanol and the fact that E15 will phase separate at a faster rate than E10, one can now understand why this becomes a serious problem for older cars or for those millions of cars that is not specifically designed to handle E15. Engines that can handle larger quantities of Ethanol blend such as E10, E15 and E85  are refer to as Flex Fuel Enabled.

IF you have a flex fuel enabled car  then this should not be a problem for you. On the other hand there are millions of cars, boats, motorcycles, ATV’s, jest skis, snow mobiles, etc that was sold in the US that is not flex fuel enabled and this warning is for all of them.

Know what you put in your tank because if you don’t, it might cost you a ton of money.

In layman’s terms.

Lets say you need one cup of fuel to make 100 horse power on E10 or gasoline with 10% Ethanol content.

If the blend is changed to now contain 15% Ethanol,  known as E15, we now will need 1 and 1/4 cup of fuel. But since we only have one cup, what do you think is going to happen. Yes … you are correct! We are not going to have enough fuel to create the power we want to make.