Porsches that should not use E10 gasoline (10% ethanol), 993 included.
03-09-2011, 01:40 PM
#16
Three Wheelin'
Geo is exactly right. Octane is about resistance to detonation, nothing more. IIRC the test to establish octane involves a one cylinder rig where the compression can be gradually increased to determine the point at which pre-ignition starts to occur. Additives are used to increase octane, the most effective of which is probably tetraethyl lead, now banned almost everywhere except for some racing applications. (remember high test gas being referred to as "Ethyl" by some old timers?) Ethanol also helps increase the octane rating but its main use is to cut the petroleum content and to reduce evaporative emissions, especially in the winter months (aka "winter blend"). The downside is ethanol has less energy content than gasoline and as Geo correctly observes it's both corrosive and tends to attract/hold water, neither of which is good for older fuel systems with plastics that aren't designed for use with ethanol. The government in its infinite wisdom has determined that up to 10% ethanol is safe but that's debatable for older cars. Over time we'll find out, possibly the hard way, if that's a correct assumption. There's not much you can do about it so I just stick with gas from major companies that have pledged to sell only tier one (high quality) gas - Chevron, Shell and Phillips.
03-09-2011, 03:14 PM
#18
King of Cool
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Thanks everyone, lot of good valuable info.
This 10% ethanol gas is corrosive, less ebergy content and tends to attract water, I mean, what's not to like..?
This 10% ethanol gas is corrosive, less ebergy content and tends to attract water, I mean, what's not to like..?
03-09-2011, 03:47 PM
#19
Drifting
03-09-2011, 04:37 PM
#21
03-09-2011, 05:00 PM
#23
Rennlist Member
I can't speak to the power aspect (related--what you can do with E85), but the lower fuel economy is a given. My friend used to travel all the time between the Bay Area and Seattle, about monthly. He bought a Yukon about when CA fuel became oxygenated (MTBE or Ethanol), and got ~17MPG. Basically freeway cruising at 70-75. Fill up in Oregon, which then did not sell oxygenated fuel? Magically it approached 20MPG. He was putting 40-50K mi/yr. on the thing, and tracked his mileage religiously.
03-09-2011, 05:17 PM
#24
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03-09-2011, 08:08 PM
#26
Drifting
We won't be able to afford food (some can't now) but we'll have crappy fuel for our cars. Its a trade-off.
03-09-2011, 08:22 PM
#27
Race Director
I can't speak to the power aspect (related--what you can do with E85), but the lower fuel economy is a given. My friend used to travel all the time between the Bay Area and Seattle, about monthly. He bought a Yukon about when CA fuel became oxygenated (MTBE or Ethanol), and got ~17MPG. Basically freeway cruising at 70-75. Fill up in Oregon, which then did not sell oxygenated fuel? Magically it approached 20MPG. He was putting 40-50K mi/yr. on the thing, and tracked his mileage religiously.
03-09-2011, 08:39 PM
#28
Rennlist Member
Which of course makes sense since you'd likely fill up in Ashland or Medford on your way to Seattle........................ (I get that there's a 1K drop from there to Portland, but it's not like dropping off the Sierras like I'm doing coming back from skiing.)
