Range and ease of long-distance travel

I got vapor lock on the Aerostar for the first 10-20 minutes at altitude. Had to run with the boosters on, or else it surged and felt like engine was going to quit. And that was with Avgas – can’t imagine how it would behave with ethanol in it!

Sorry, no, once again, alcohol /ethanol is NO problem for all rubber material used in motor environment. And you will most likely NOT find it in reasonable percentage in common mogas or auto fuel when it does not have to be in there like with E 5 or E 10 “green fuel” . It is just not economical for the factories to add. Problems to seals and hoses – and vapour/ cavitation effects are related to all those components/thinners that are called gasoline nowadays, like acetone, toluol, ether, etc. . I invite you to do your own test and place some NBR o-rings in ethanol and auto fuel. After a short while you will notice that o-rings will be wider in diameter and quite soft in the auto fuel mix but NO change in alcohol. You will have to use Viton when playing safe in mogas, or teflon, of course. The softening may be no problem when an o-ring is in a confined space, it does not dissolve. But with seals on rotating shafts like in fuel pumps that will lead to leaks as the diameter of the lip will increase too much, so only Viton there in doubt. Another problem is cavitation in pumps when using mogas (thinner fuel) in hot times. In a low wing aircraft you better add another feed pump right after the collector tank low down in the fuselage to avoid sucking problems in the engine pump in the take-off run. We are using super 98 from the filling station from first day and no troubles after fitting the additional feeding pumps. Vic

Ethanol does not matter one bit regarding vapor lock. The refineries blend the cocktail so the vapor lock is according to standard due to environmental issues. It will be the same if it is 0% or 20% ethanol, at least in Europe. Modern cars doesn’t care either way, there are no low pressure areas in a modern car fuel system. For this reason the gasoline you purchase in the summer may be very different than the fuel you purchase in the winter. You need to start a cold soaked engine as well, and this may be difficult using summer fuel, it wont evaporate as easily. Using winter mogas fuel in the summer may be a bad solution if vapor lock is a problem, very bad for aircraft for sure with their antiquated fuel systems.

I wonder about those STC for mogas. Mogas is very far from a constant thing. It varies widely. The main problems has nothing to do with ethanol as such, but vapor lock due to different blends with seasons (regardless of ethanol) and in-tank storage over longer periods of time (due to ethanol). How do you “STC” yourself away from these problems?

Using mogas every now and then, cannot possibly hurt anything IMO, considering the octane rating is OK. But the less the aircraft is used, the better it is to use avgas, regardless of STC or not, or Lycoming vs Rotax for that matter. 100LL and UL91/Hjelmco are much better fuels for a typical GA aircraft than mogas is (IMO at least. Just because you have an STC that makes it legal to use mogas, doesn’t mean mogas is just as good as avgas, it only means that mogas doesn’t hurt. Avgas is a more strictly specc’ed fuel)

Lycontisauri can be made to work with normal car fuel (that may contain ethanol). I got home from Yorkshire on the weekend in a mogas fuelled Jodel with a Lycoming O-200 in it.

On the other hand, ethanol containing fuel isn’t ideal for the reasons stated, it’s also a little bit less energy dense. Not such an issue for an O-200 or Rotax powered aircraft which doesn’t have a particularly high fuel burn, but I suspect the fuel flow increase would have to be noticeable with E10 and a big engine.

Sure it wasn’t a Continental O200?
We have no problems getting ethanol free car fuel – many local filling stations get it from a depot supplied by a ship tanker, and the local depot still hasn’t the equipment to add ethanol. Also applies to islands supplied by ship tanker, as opposed to a road tanker on a ferry.