Rick: "1) It raises the octane rating. 2) It cools the valves. 3) It lubricates the valve guides."
Me: 1. Yes it is in the fuel to raise the octane rating. 2. It does not cool anything - a myth that I can not see how that can be justified. 3. It does not lubricate anything. Lead-oxide acts a layer on valve seats that used to dampen the valve when it is hitting the seat. Back then seats could be just made from non hardened material when leaded gasoline had been used. Nowadays any cylinder sold has hardened seats for the valves. No need to have a layer of lead-oxide there or at the valve stems, where it actually destroys the valve guides. Just think about it. The burned gases are being pushed along the exhaust valve while the valve is pushed down, exposing the stem to the gases. When the valve closes, you don't want a layer of some hard oxide of anything on that stem. This is because the stem slides into the valve guide, which should be tight against exhaust gases. So, ideally , you want the valve guide be able to wipe off any of the stuff that it is exposed to. It has been found that lead oxide is too hard to be scraped off, hence the sticky valves. Mogas on the other side does not leave hard oxides on the stem, therefore we are in favor for Mogas. Hartmut ----- Original Message ----- From: Rick To: [email protected] Sent: Sunday, March 02, 2008 7:30 AM Subject: [ercoupe-tech] Miscl, ethanol, slosh Guys, I've got a couple of things that are troubling me. We've been talking a lot about ethanol in MOGAS, but in many states an oxygenate is mandated, but not a particular one. For instance, in California, until recently MTBE was the required additive. That basically destroyed the carb on my 1969 BSA motorcycle. I can't believe it would be much better on our Ercoupes, but I don't have evidence. Others are pointing at the ethanol that replaced the MTBE. There's no question about it. Alchohol in any form has an affinity for water. That may damage our fuel systems. Is that worse than lead fouling? It is certainly illegal. I don't have the answer. What is the lead for? My understanding (which might be wrong)is that the lead serves 3 purposes. 1) It raises the octane rating. 2) It cools the valves. 3) It lubricates the valve guides. If I am wrong or incomplete on these, please tell me. If not, it seems to me that we are better off with an AVGAS with ills that we know than a MOGAS that varies with political whims. We have another issue that should probably be a separate post, but I'm lazy. there have been a number of posts about leaking fuel tanks. All have mentioned that sloshing the tanks is horrible/nasty/illegal/badbadbad if you are using MOGAS. I'd like to pause for a sanity check. It is certainly illegal, BUT, if it is bad for MOGAS, it's probably as bad or worse for AVGAS, just not illegal. Here's my justification for saying that. I've looked at the ingredient list for this stuff for aircraft and for motorcyles. I've emailed the manufacturers of both. I've dealt with motorcycle tanks done with the bike version. I can't find a dime's worth of difference in the AV vs. bike slosh and it deteriorates with every kind of gas. I've been dealing with slosh coming off for well over 20 years. I absolutely can't tell the difference between AVGAS, MOGAS, MOGAS with oxygenates, MOGAS without oxygenates. Slosh is great for a little while, but no matter what kind of gas you are using, eventually, it flakes. Quite frankly, I am one of those guys who really doesn't give a damn whether it is legal or not. What I really really care about is whether it is safe or not. If it's not safe for me to run in my bike, I don't think we should be flying with it. Am I over simplifying? Wouldn't be the first time. Rick Hoover
