Contour Enthusiasts Group Archives Forums General Troubleshooting gas milage sucks - 350 km on a tank

Originally posted by Ray:

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In the case of the SVT, premium fuel is required because of the timing of the car. Placing anything lower will save you a few cents on gas, however, the timing will be cut to compensate for this, your car will be in "safe-mode", so to speak, and you will lose any benefits you just gained from getting cheaper gas, because you now get worse mileage and have to fill up MORE OFTEN.

Ray

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Would running 87 in an SVT cause a too lean condition or bad mileage? The owner of the vehicle prior to me stated he never put premium in it and it ran just fine. So I have never put it in there despite it saying on the guage "premium fuel only" Same thing with my dad's 2000 GT mustang - he never puts it in there and it runs great.

Just wondering.

Originally posted by tktrain:

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At the risk of opening a large can of worms, I'll throw my 2C worth into the mix:

I assume that when you say "Ethanol" you are actually referring to gasohol, a mixture of 10% ethanol and 90% gasoline. If you where to run pure ethanol you would consume roughly twice the volume of liquid in the same number of miles (kilometers) as gasoline. This is because ethanol contains roughly half the potential heat energy as gasoline.

On the plus side, ethanol has a much higher octane rating than does gasoline. If memory serves, it is about 110 octane in its pure form. Adding about 10% ethanol to gasoline will raise the resulting octane rating by around 2 points, IE: an 87 octane pure gasoline would become about 89 octane with 10% ethanol added. Ethanol has a great ability to absorb water; this is why it is used as the main component in gas drying additives. Ethanol also contains free oxygen which will promote the more complete combustion of the hydrocarbons that are present in the combustion chamber. This means the fuel and any oil that finds its way past the rings and valve guides. Generally speaking, gasohol will help clean-up the tailpipe on higher mileage vehicles.

Cars can use a 10% ethanol mix with usually no issues at all. Cars built back in the sixties and seventies sometimes had problems with gasohol due to seals and hoses that would react to the ethanol by swelling and distorting. Current production vehicles have been designed with gasohol in mind and will almost without exception work fine with gasohol.

Gasohol should not affect your car's running rich or lean much, if at all. It could allow the PCM to call for slightly more fuel than with non-gasohol, but this would only be due to the fact that the combustion process would be more complete. This increase in fuel per pound of air would be offset by the rise in combustion efficiency.

This is all based on a graduate level mechanical engineering class I took back in the 1979 era at Purdue University on combustion and air pollution.

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Originally posted by dutchie:

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yep, an ethonol blended gas. only drawback I heard is that it clogs your fuel filter more often.

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The clogging is likely a result of the alcohol acting as solvent and dissolving varnish deposits in the tank and lines. This should stop after a while after the ethanol has "cleaned up" the fuel system. You might consider using a good fuel system cleaner in a couple of tanks before making the switch.