The demise of 100LL is no surprise

At the recent AOPA Aviation Summit, several industry leaders made the startling comment that lead in avgas is going away. Well, duh, what do you think I have been saying for the last 20 years?

The comments fall into three general areas: The first is the gloom and doom group that feel that it is all over and that we should just scrap all of the planes and have everyone in GA go find a new hobby to dump money into. The second group is in denial — they do not believe the EPA will actually go through with its threat to outlaw leaded fuels. And the third group believes that someone will come up with a miracle fuel that will replace 100LL, cost less, and perform better in all applications.

For the third group, I was going to say that there really isn’t a Santa Claus, but I am sure that these people still believe in the jolly old man.

The second group is almost as naive as the third group. The EPA is going to regulate lead out of avgas. The question is when and has nothing to do with facts or data. The people at the AOPA meeting were guessing that it will go away in the 2016-2017 time frame. That’s a good a guess as any, but I would remind people that there are several elections between now and then, so things can change quickly. And I have seen a lot of deadlines given, starting with 1995, and they have all come and gone.

For the first group, don’t despair — there is some hope. Pilots with non-turbo/super-charged engines have nothing to worry about. When the new unleaded fuel does finally appear, your engines will work well. Other than changes at your next overhaul, it will be basically an invisible change. On the positive side, all of the 80/87 engines and Rotax 4-cycle engines will finally be able to buy fuel at any and all local airports.

On the negative side, there is the very real problem of turbo/super-charged engines and the big radials. These will all need to be modified in some way and someone will need to re-qualify and then be legally liable for the proper operation of these engines on the new fuel. This may mean that some of them — especially rare models — may become static displays.

The thing that got me most were the comments such as “GA is scrambling to find alternatives” and “We have just one shot at this, so we need to make the right decision.” Where have these people been? For the past 20 years there has been only one solution to what the unleaded fuel will be, and that is a fuel made from the same components as 100LL, only without the lead and with a lean rating of around 94.

This isn’t rocket science or magic, it is just common sense, which is in very short supply. We don’t need industry leaders who go around screaming the sky is falling. We have elected officials to do that. What we need is leadership who will actually lead and start working with the EPA and others to try and make this transition as safe and painless as possible.

Ben Visser is an aviation fuels and lubricants expert who spent 33 years with Shell Oil. He has been a private pilot since 1985. You can contact him at


  1. Marcellette says

    Thank you Bob Atkins for the best explanation of the real problem with the leaded avgas I’ve seen yet (and I’m writing part of my MBA thesis on it so have done a LOT of research). Question to you: do special metal chemical coatings exist to help extend the useful life of the exhaust valves?

    As for an additional comment along the same lines as everyone else, it appears many different unleaded versions exist for aviation (82UL, Hjelmco Oil’s 91/96 from Sweden but also used in Japan, mogas, AGE 85, and soon Swift’s 100SF?). EPA has made the decision in October 2008 to change the amount of lead in air from 1.5 micrograms/m³ to 0.15 micrograms/m³ effective 2017 and these measures are aimed at non-road vehicles and other stationary platforms. A study carried out after the Friends of the Earth’s petition in 2006 to the EPA on the amount of lead emitted by GA revealed that granted Ed Rosiak’s comment about the amount of avgas manufactured in the U.S. compared to motor/other gasolines is such a small percentage, GA emits 45% of the ambient air lead inventory. I’m not so sure the lead issue is just about tree huggers – it’s about public health issues too. Lead causes brain damage in babies resulting in reduced IQ in children. It causes an increase in blood pressure, cardiovascular disease, and kidney malfunction in adults. I love flying and can only fly little Pipers, Cessnas, and Decatholons, (and would really like to get in those Cirrus) etc., but this ruling is in the public’s best interest. As mentioned earlier – this problem’s been known for 20+ years. Put me in group 3, granted I’m sure it won’t cost less. The concern to me isn’t so much the alternative but the costs for using alternatives (more frequent overhauls of engine/fuel delivery system modifications) and establishing production and distribution for any of the alternatives so we can keep flying seamlessly.

  2. Ed Rosiak says

    Ben left out the real reason for the demise of 100LL. The enviro-zealots are suing the EPA to make themselves look good, and get contributions. Even though 100LL is less than .01% of the gasoline manufactured in the U.S., and it will make no difference, it is of no concern to these people who are pushing their own agenda.This is always about money regardless of how genuinely concerned about the earth they want you to believe they are.

  3. says

    There is no question that leaded fuel is going to go away however, as Mr. Visser pointed out – many deadlines have come and gone. Many view this as an eviro/political issue but few realize that the lead in 100LL may go away one day without warning or political effort. There is only one company left in the world that makes tetra-ethyl lead and if and when they stop – that’s it – we will have unleaded fuel. The inside joke in the industry is that we are one explosion away from unleaded fuel.

    Another major issue that is conveniently sidestepped every time I read about the demise of leaded avgas. The concerns are always centered around detonation and octane. Lets get something straight – 110 octane unleaded fuels exist today in racing fuels so octane isn’t an issue.

    THE MAJOR ISSUE is exhaust seat/valve erosion. You say – what? Yep – the really nasty secret is that once lead is gone from the fuel – every air cooled engine will have a considerably shorter operational life span. Why? Well, in spite of the fact that there are already hardened exhaust valve seats in virtually all air cooled engines – when operating at 700-900F (the avg temp of an exhaust vale seat) without lead to buffer between the exhaust valve face and the seat you will get rapid micro welding and diffusion erosion between the valve face and seat. The result is the erosion of the valve seat, taking up all of the slack in the valve train and when the exhaust valve can no longer close, in a matter of seconds/minutes you end up with a burnt exhaust valve.

    That is the real dirty secret of what unleaded fuels will bring. Detonation is a trivial matter given that 100+ unleaded octane is easily achievable.

    So how long will it take to burn the average valve in say a normally aspirated O-360 engine? Plan on about 500 hours – max! Turbocharged engines will be way shorter at around 150-300 hours.

    How is this possible you ask? I know people flying with unleaded autogas today and they don’t have any problems. Perhaps not but that is likely because of the re-introduction of lead periodically when the aircraft is fueled with conventional 100LL on occasion. Also, many engines running on auto fuel STCs are low compression, low power engines that run considerably lower exhaust seat temps.

    So you can put me in group #1 (gloom and doom) or you can be in group #2 (denial) – either way there is no substitute for the job that lead performs by creating a dissimilar metal coating between the exhaust valve face and the seat. This is why you don’t see air cooled engines on the road any more. How come? Well, when you water cool the cyclinder head you bring the temperature of the exhaust seat WAY down – to around 300-400F at very high power levels. At this lower temperature, the seat maintains its hardness and limits the micro-welding and diffusion erosion. The lower seat temperature also keep the face of the exhaust valve much cooler. Cooler metals are harder and don’t tend to micro weld and diffuse when slammed into each other.

    So – in the end air cooled piston engines will have to go the way of the dodo bird when unleaded avgas becomes a reality or you can plan on pulling your cylinders every 500 hours or so to replace to the exhaust valve seats.

  4. Bart says

    Mr Visser is exactly right, AOPA and other “industry leaders” should take note. This is not all that difficult and it will ultimately benefit most avgas users to lose the lead. For most of us, even like myself flying a Continental IO 520 powered Bonanza, lead is something I deal with which causes maintenance headaches and little benefit. The big guys, who mostly fly big radials for commercial purposes or war birds for fun, have a problem, but they aren’t a large portion of the GA fleet.

  5. says

    Once again, you fail to mention the drop in replacement fuel that is under development. While it isn’t here yet, the technology is and GA is the perfect place to start with the 100 octane drop in replacement engineered by Swift Enterprises. The ASTM testing of the Swift fuel has demonstrated it to work quite well as a drop in replacement. I don’t even begin to belief the myth that it will be cheaper, but if it is competitively priced with today’s fuels I’m all for it. There is no need to shelve older planes or force expensive overhauls onto high performance planes.

  6. Rick Lanman says

    What he said.

    To their credit, the EPA is now looking for information about how General Aviation works before attempting to issue regulations. While I am also skeptical on how they will apply the information, I can think of many other regulatory bodies that cvould take a lesson. Required lead monitoring and looking in to the actual impacts of lead on the air quality around airports are appropriate measures before establishing regulations that could really damamge an industry.

    That said, Mr. Visser’s comments are just as true today as they were 15 years ago. Thank you, sir.

  7. Karl D says

    I liked Ben Visser’s article. They are always very straight forward and to the point. Here are my thoughts after reading articles and concerns from other aircraft owners.

    Concerning the three schools of thought:

    1. I don’t believe a switch to unleaded fuel is the end of general aviation or old aircraft. Baring any FAA interference, people will find a way to adapt their procedures, techniques, and technology to keep the aircraft flying.
    2. I believe the EPA will eliminate lead from avgas. The public has been taught lead is very bad and it’s a huge political football. If the entire automobile industry could not stop it, I doubt if general aviation can stop it. We receive a reprieve when they eliminated lead from auto fuel, times up. We saw the hit general aviation took when the automobile execs flew in to request TARP funds. Just think what happens politically if public perception is a bunch of people are flying around with lead, that could hurt their children, in their tanks.
    3. Any alternative fuel, like Swift fuel, will require vast amounts of capital and time to grow their network for general aviation. It will require building refineries and distribution network. That cost will be passed to the consumer, and I don’t believe it going to be cheap. I think it is something we could be using in the future not just for general aviation but even our automobiles. I think it will take time to move it into place.

    I think their will be no easy transition, there will be problems. I also believe we will work our way through it.

    I think whoever decides how to distribute the fuel should perform it in stages. I would look at the aviation community in geographic hubs and the routes they take. Determine if there is a pattern to where the lead requiring aircraft are stationed and their routes (like truck routes). Work with gas networks to distribute leaded avgas to some airports and unleaded gas to other airports around the hub and routes. It would be like having some gas stations along the road with diesel. If the unleaded fuel is cheaper because there is no lead, I would flock to that airport where the cheap fuel is (although I’m not sure if unleaded fuel is going to be cheaper). The people who need to use the leaded fuel can still get it for awhile until they find a sublimental technology such as electronic ignition. This will also give the high performance aircraft time to adjust and plan how to keep their aircraft flying.

Leave a Reply

Your email address will not be published. Required fields are marked *