Do you require 100LL?

The question is do you currently require 100LL for your flying RV, or will you require 100LL for your RV when it flies?

According to Superior, the parallel valve IO-360 that I bought from them for my RV-7 is rated for car gas. After experiencing the improvement that unleaded fuel made to the sludge... er, oil, in the crankcases of my motorcycles back when car gas made the switch, I'd be completely happy to never burn a liter of 100LL. Probably gonna be flying before that becomes practical though.

42% need it? Yeah, right.

You should have clarified who actually needs 100LL. If you're running 9.5:1 or better compression in a Lycoming, you need 100LL. If you're not, 95 (or even 93) octane unlead will work just fine. How about a new poll for people running better than 9.5:1 compression?

I would like to see a push for 95 unleaded gas for aviation available. That way we can see how many people actually will use that 100LL stuff.

I know when auto gas went unleaded there was the same type of discussions. The unleaded gas was slowly brought in and then the leaded was taken out all together. What I noticed after that was a much better engine, better technology. So get rid of that 100LL and bring on the better engine.

I am using 9.5:1 pistons

Hence my YES vote for 100LL. Now whether I need the lead at its current level is unknown. Supposedly I need the octane to prevent detonation but even that may be unneeded IF I keep CHTs under some TBD value.

Ron Lee said:

Hence my YES vote for 100LL. Now whether I need the lead at its current level is unknown. Supposedly I need the octane to prevent detonation but even that may be unneeded IF I keep CHTs under some TBD value.

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Yes, if you have a certified lyc, you need avgas.

95 and 98 octane!

Here in Europe we have 95 and 98 octane car gas (some places may also have 91 octane).
So, if you check all your seals, O-rings and gaskets in the fuel system for compatibility with ethanol and design your fuel system correctly (f.e.: return line to the tank) running on car gas should not be an issue for an experimental. All the Rotax guys have been running car gas for many years now!

osxuser said:

Yes, if you have a certified lyc, you need avgas.

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Having a certified Lycoming has nothing to do with it. Maybe I'm not getting your point? It's all about compression ratios with Lycomings and clones.

jonbakerok said:

You should have clarified who actually needs 100LL. If you're running 9.5:1 or better compression in a Lycoming, you need 100LL. If you're not, 95 (or even 93) octane unlead will work just fine. How about a new poll for people running better than 9.5:1 compression?

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I was running 10.5 : 1 pistons in my 0-360 and used a mixture of 50/50 92 Octance car gas & 100LL. Worked great, and saved about $40 everytime I filled up. Mixing is an option also.

Isn't the real question whether air cooled engines can lubricate exhaust valves adequately w/o lead additives? Valve failures are already one of the sensitive areas with air cooling- going to nonleaded fuel might just make that problem worse. I believe auto engines use hardended valve seats to allow nonleaded fuel.

Valves

One of the issues. It is easy for some to say...just put in a new engine. Put in a diesel. Put in a Rotax. Put in a french fry oil burning engine.

I just rebuilt an O-360 with 9.5:1 pistons. Forcing people to make expensive changes with questionable benefits is like the ADS-B Out NPRM that people are ignoring and will cost you thousands with no benefit.

You will see in my response to that NPRM a chart that shows 100LL fuel deliveries way down. Any lead put into the atmosphere has already been cut substantially.

http://tinyurl.com/2wem8j

After I moved to the airpark, I started burning about 50/50 av/mogas. One tank was for auto, the other for av. Takeoff/landing was done on the avgas (better vapor lock protection). The engine (O-360, 8.5:1) loved the car gas and ran cleaner. Plugs stayed cleaner, just all around happier and cheaper.

I just paid for the Petersen STC for my Skywagon...$345 for that! (Certified airplanes are a pain sometimes...)

My buddies across the street...Cherokee 235 and a C-120 both have burned mogas exclusively for many years. It's great...but stinky.

Once you go over 9:1, octane becomes an issue. Certified or not, once it's put into the experimental airframe, it is no longer a "Lycoming". It's just an engine. Feed it whatever it likes.