Autofuel experience

Dear Community,

I am Michael from Germany and I am brand new in this forum. So hello to all. And I have a question in regard to your experience in using autofuel. I found some threads but after reading them, it was not really clear for me. Furthermore the threads I found were pretty old already.

I recently bought a RV6A from 1992 with a Lycoming 160 hp engine O-320 D1A (both tanks are sealed with ProSeal 890). The former owner used 100LL only.

I would like to know if I can use autofuel or do I have to expect some trouble?

The Mogas/autofuel is called SuperPlus (98 octane) here.

It would be great if you could tell me your experience in that matter.

Thank you in advance and please excuse any mistakes in English.

best regards
Michael

You have a 160 hp O-320 so that tells us that your compression ratio is higher than the 150 HP version.

Also O-320 means you have a carberator instead of a fuel injection.

Few thoughts....

If your timing is set properly I do not think the engine will have any problem running into detonation. The engine should burn the Mogas just fine.

Any idea what the Reid vapor pressure of the Mogas is there and if it changes from Summer to Winter?

A carburetor is pretty good about letting any gas bubbles release without causing the engine to in rough at idle.

Main concern I would have, Make sure there is not a lot of restriction between the engine driven fuel pump and the wings. If you do have any vapor lock issues it could likely be overcome by running the boost pump but you really don't want your airplane to be "dependent" on the boost pump.

Michael,

Welcome to VAF!

I have been using ethanol-free 90 octane auto gas in my RV-6 (O-320, 160 hp, carb, magnetos) for several years. I have not had any service problems related to the auto gas.

Enjoy your new RV.

Alcohol

Hi Michael, just make sure it's not Super Plus E10, which contains alcohol. You can theoretically use that too, but you need to confirm you have the right kind of rubber in your entire fuel system. Viel Spass!

Hi Michael,
I´m flying two RVs almost exclusively on autofuel, but I planned accordingly when building. The planes are very well tested on autofuel and I can give you more details when interested, just PM me.
Super Plus 98 can contain up to 5% Ethanol in Germany. Although this might be ok it is better to avoid. There is no Ethanol added to ARAL Ultimate102 and TOTAL SuperPlus Excellium, both companies replied with this answer when I asked. I do test the fuels now and then for Ethanol and never found some.
BTW I´m flying out of EDMG, not far from Stuttgart.

I've also run non-ethanol premium mogas in a 160 hp O-320; in my case, for at least a decade. My only issue was due to my own carelessness. 'Winter blend' gas, 100+ degree (F) day, heat soak on a ramp after a flight. Then after subsequent takeoff, rough running engine and precautionary landing.

As Weasel mentioned, it's worth checking on vapor pressure of *your* gas in your area. It varies quite a bit around the country here in the USA. If I were a betting man, I'd be betting it's less of a problem in Europe, since higher vapor pressure means more pollution, and we seem less and less interested in that issue here...

Guten Tag!

Welcome aboard.

Don't know about Germany, but in the US "octane" for car gas is measured differently than "octane" for avgas. Car octane is usually 3 or 4 points higher than the avgas standards, e.g. 87 car gas is about the same as 83 avgas. Use some caution.

I have also used MoGas in an RV-6 that I built with the same engine. It was sold over seas about 2001 or so and went to the UK. (HMMM)
Anyway, I ran high octane ethanol free car gas in it all the time; however, I did find that mixing some 100LL in with it, about 15-20%, prevented vapor lock, especially when we had the seasonal gas formula change.
(Additionally, I think the lead from the added 100LL helps lubricate the valve guides and may even boost the octane of the lead free car gas a little. Just my guess.)
I believe there is a different thread somewhere containing a discussion on octane calculation and your 98 octane is comparable to our 93 octane, just a different calculation.

sf3543 said:

I have also used MoGas in an RV-6 that I built with the same engine. It was sold over seas about 2001 or so and went to the UK. (HMMM)
Anyway, I ran high octane ethanol free car gas in it all the time; however, I did find that mixing some 100LL in with it, about 15-20%, prevented vapor lock, especially when we had the seasonal gas formula change.
(Additionally, I think the lead from the added 100LL helps lubricate the valve guides and may even boost the octane of the lead free car gas a little. Just my guess.)
I believe there is a different thread somewhere containing a discussion on octane calculation and your 98 octane is comparable to our 93 octane, just a different calculation.

Click to expand...

I thought that the lead was to lube the valve seats? back in the day the machine shop I used was installing hardened valve seats in the heads of older 60s-70s muscle car engines to run unleaded fuel.

Not much to add.

As all the good advice above has it. I will just tell you we run an IO-360 with 9:1 ratio pistons in it. We use 100LL and 92-93 UL with no "E" in it and mix them about 50/50 for the most part. In summer we try to run 100LL and only go above 75% power if needed. But for the most part we have found that the 92-92 UL, just helps keep the lead from forming on the plugs and out of the oil for a lot longer. With your lower power and compression I would think that running UL of 92 or above should not be a problem at all. Many of the engines here in the States are "STC'ed" for these fuels. By the way, some very good cars from your home town and good friends of mine as well. The "E" fuels can attack and degrade some of the older gasket and rubber parts that were made years ago in a fuel system. What would worry me more with your set-up more than the fuel burning OK in the engine. Yours as always, R.E.A. III # 80888

I ran 87 Octane unleaded 0E fuel in my C-172 for hundreds and hundreds of trouble free hours. Summer, winter, no problems.
We would feed from one tank at a time when at cruise altitudes, rather than the fuel selector being on "both".
This procedure was recommended by Cessna to avoid vapor lock.

bret said:

I thought that the lead was to lube the valve seats? back in the day the machine shop I used was installing hardened valve seats in the heads of older 60s-70s muscle car engines to run unleaded fuel.

Click to expand...

The lead was used to increase the octane of gasoline, not as a wear additive. However the lead also protects the valve and seat interface points from wear, allowing the manufacturers latitude in material selection. When lead went away, hardening of the valves and seats was required to avoid wear. Just like when we added ethanol, manufacturers had to change materials to deal with it.

Larry