Ethanol is completely soluble in motor gasoline. There should be zero concentration gradient if sufficient time and or energy has been expended to let the blend equilibrate. However, ethanol is VERY soluble in water. Thus any distribution system that is "wet", ie has water in the tankage, will have a much lower ethanol concentration in the mogas than specified. Any reputable distributor will be sure their system is as dry as possible. It is this issue of water solubility that leads to the addition of ethanol to RBOB, a blend that requires alcohol to meet octane specs, at the final terminal before being trucked to your friendly local gas station.
VaCouper N3000G --- In [email protected], [EMAIL PROTECTED] wrote: > > A couple of concerns: > > 1. The mix of gasoline and ethanol is not necessarily homogenous, meaning > that the total in a gas station tank may be 10 % ethanol, but the portion > you actually pump out may have considerably more, or less, than 10 % > ethanol. That will take all the predictability out of mixing it with avgas > to keep the ethanol to less than 5 %. > > 2. I may be wrong, but I am not sure there is approval for a mix of mogas > and avgas. I like the idea, but would be concerned about insurance picking > up on it and denying an engine failure related claim. Anybody knows? > > Sorry for raining on the parade... > > Eliacim > > > > Here are a few things that I have found out about fuel in the past > > few days. Since the Mogas STC does not allow for automotive gasoline > > that contains ethanol, the question was asked about where you can > > get gasoline that does not have Ethanol. I thought my sport pilot > > instructor had a source in California. That was partially true. > > Apparently "all" gasoline sold in California has between 4% and 6% > > Ethanol. Through the Ultralight forums, there is a list of the exact > > amount of ethanol in the gasoline that each company is producing. > > Right now Mobil is low and ARCO is the highest in California. My > > instructor buys from Mobil and mixes 100LL aviation fuel to reduce > > the Ethanol percentage. The Rotax engine can tolerate up to 5% which > > is the same percentage that is listed in the EAA STC for mogas as > > the absolute-don't-use-it maximum. > > > > In some states, only E10 (10% ethanol blend) is available by law. > > Some states have passed laws that the premium grade of automotive > > gasoline contains no ethanol. In California, there is a mandate to > > move to E10 by 2010 but the refineries will need to invest in their > > transportation and handling infrastructure to support that. > > > > Relate to this discussion is the news that TCP will begin production > > of TCP again around April of this year. They had some problems with > > their packaging that tended to leak. The EAA recommended that > > people use the auto fuel STC in the meantime. They also suggested > > mixing 100LL with auto fuel to provide the same benefits of STC with > > respect to lead fouling. They recommended a mixure of three- fourths > > autogas and one-fourth 100LL which would contain the same lead > > content as was allowed in the 80/87 octane aviation fuel (suitable > > for the Ercoupe). > > > > So it seems that mixing 100LL and ethanol-blended auto gas will > > solve both the lead problem and the alcohol problem. If you only > > have E10 available, it looks like you would have to mix 50-50 to get > > the percentage of alcohol down to 5% or lower. At that point the > > lead content is half as bad but not yet done to the level of 80/87 > > avgas (no longer available). A higher mixture of mogas can be used > > if the actual alcohol content is less than 10%, but it will require > > some research and/or testing to know what the content is to ensure > > that the mixture does not contain more than 5% alcohol. > > > > Of course the use of 100LL is the other option which will need TCP > > available to mitigate the risk of lead fouling. WOW we practically > > have to make our own fuel to provide the right fuel for our birds. > > > > Frank Nelson > > N51DV 415C > > TOA/California > > > > > > >
