Corvair Oil Change interval….. Lessons part #1


Quick Quiz: William gets a little depressed around the holidays because:

1) That is an appropriate reaction to seeing masses people shopping, wandering around like zombies text messaging on I-phones and very few people considering what is really worth living for.

2) His birthday is the last week of the year, and when you’re in your 50’s it’s hard to pretend your 24 years old anymore and not pay for it the next day.

3) His private question “I am supposed to be a great engine teacher, What have I accomplished this year?” Must be reconciled with the actions of builders who made some really foolish mistakes this year.

If you chose any of the answers, you are correct, but if you chose answer #3, you are also getting to a topic that distresses me all year round. In this short series, I am going to cover examples of people who made mistakes with their engines.


Some basic rules on this: A) Make a mistake, even a dumb one, and I don’t use your name. B) Make the same mistake a second time, and I reserve the right to use your name in the story. C) If you go on the net and complain about the effect of your mistake, but don’t understand that it was your mistake causing this effect, 50% chance the story has your name in it. D) If you make mistakes all the time because you want to argue every paragraph on my website, but also complain that the engine doesn’t run like I said it would, then your name and photo are going in the eventual story.

Why this matters: Two fold, I need people to slow down, read and ask questions. Every time people make mistakes like this, It puts them at unnecessary risk and it gives Corvairs a bad name. Even if the guy doesn’t complain on discussion groups, every person at his home airport sees his issues and says ” That’s because it is a car engine”.  None of those observers look and understand that they were looking at a self-inflicted wound. The observers are the people who always say “We had a guy with a Corvair at our airport, nothing but problems.”

They never stop to think that the same guy would have had issues with any engine he had. Corvairs like to have the oil changes, but so do brand new O-200s. Some times peoples mistakes, their public demonstration of these self made problems and the stupid comments people make about them lead me to wonder “Where do I do to restore the reputation of my 25 years of work with the Corvair?” Unfortunately, the only answer is that reputations are a commodity that are built very slowly over time with a 1,000 good examples which are very easily destroyed by a few careless people. Everyone who takes their own life work seriously has challenges, and this is mine. It has no good nor easy solution, we are left with just stories about lessons learned.

For the serious builder, take heart. for every guy out there messing things up, there are two dozen having no problem at all. The most important thing to understand here is that these mistakes don’t strike builders at random. I am going to spend some time here showing that individual personalities, like being in a rush, not respecting details and thinking you are to smart to listen to me are all the root of these mistakes. They are not random, they have nothing to do with experience nor IQ. They have to do with personality traits that are poor matches to serious work like engine building and flying planes. That is what you need to take away from this.


2013 saw a long standing record broken in the land of Corvairs. This was done right at Oshkosh, in the row Ken Pavlou reserved for Corvair powered planes, right behind my display booth. I should be really happy about that right? Guess again. The record was Longest time flying on the break in oil that should have been changes at 30 minutes to 1 hour: The new mark, set by a builder who had flown in from the east coast is 86 flight hours on the break in oil. It had never been changed, and was several years old.  This took the previous record away from the person who set it in 2008, flying to a College with 56 hours on his break in oil.

Is this a Corvair issue? No, these guys would have done this to any engine they put in their plane. I have a hard time understanding how a person would spend the time carefully assembling and engine and they go about poisoning it. Both of the guys are smart enough to get paid a very good living, but they are both from the “Office building” world, and have little exposure to mechanical things that need some level of care. Both have busy lives and may not have focused attention on their operation. Although neither engine broke because of it, I am sure that the life spans of these engine was shortened by 50% or more.

Two years from now when they are overhauling their engines, and people at their local airport walk past and say to each other “Didn’t he just build that? I guess car engines don’t last.” These builders will not do me nor the Corvair the justice of hanging a sign outside their hangar which says ” Self inflicted wound. I tried to extend the recommended initial oil change interval by a factor of 100.” It is worth noting that neither of these builders thought they were doing anything wrong. It came up in conversation, so I don’t actually know how long they were going to go, it could have been 100 or even 200 hours. I try to be an optimist, but right now, I am sure we have a builder somewhere, who will not read this, who will try to break the 86 hour record.

Should Mr. “86 Hours” have known better?: Yes, I published this story: Notes on Corvair flight engine oils. about a month and a half before he left for Oshkosh. It specifies 25 hour intervals. Also, the plane was more than a year old, and should have had a yearly condition inspection by federal law. If the oil wasn’t changed, the inspection was bull shit. The A&P who did it needs his license jerked. If the builder did it himself, he needs his repairman’s certificate rescinded, and if he didn’t bother to get a Repairman’s cert for his plane or have an A&P look at it, the plane flew to Oshkosh illegally.

The Corvair is a very tough motor, and I changed the oil myself at Oshkosh at night. I cut the filter open and there was almost no metal at all to be found. I expected damage, but I was just guessing, because in all the testing I have done in 25 years, none of it included seeing how long I can run break in oil in an engine without making metal.

OK, what about Mr. “56 Hours?”: He should have known better also. lots of people claim that information was not easy to find on our webpages. OK, I took me 60 seconds to go to, go to the bottom of the page and type “Oil Change hours” into the search box and it spit out the 2007 story I have reprinted below. I am sorry if that was too hard.


From 2007:Above, Fred Roser’s engine on the dyno. The photo is a reminder that we prime, test run and operate Corvairs on  Shell Rotella T 15W40 oil. Although everybody has a favorite oil that’s served them well on projects years ago, several  industry experts have told me that the formulation of many favorite oils has been changed for environmental reasons, often  compromising break in qualities by eliminating metallic based additives. Since we test engines on Rotella all the time,  builders can be confident that the current formulation of this oil works well in our favorite engine. We change the  oil and filter at 1 hour, 5 hours, 10 hours and 25. As KRVair Builder/Pilot Steve Makish pointed out, he’s yet to see an engine hurt by  having the oil changed too often.”

5 Replies to “Corvair Oil Change interval….. Lessons part #1”

  1. Happy Birthday and Merry Christmas William!

    Project is on hold but I still enjoy reading your articles, they have a little of everything; philosophy, theory, decision making, engine building and a the arts (Neil young).


    Sent from my iPhone

  2. William,

    Happy Birthday in advance of tomorrow, first of all. Second, don’t let the idiots get you down (too much). There are too many success stories of Corvair builders and flyers for the idiots to do permanent damage. Just keep doing what you have been doing and the growing Corvair community will keep giving you examples of good decision making. Besides, you can never totally eliminate bad decision making in a free society. Just remember that everyone is good for something, if only to be a bad example.

  3. William, Happy Birthday and hope for a GREAT new year to you and yours. My wife and I recently were blessed with jobbs, (the spelling is on purpose because after 35 years of self employment, “jobb” is somewhat of a 4 letter word.) The good news is there are Gold parts in the new budget!!

    PS Still looking for the definitive answer of how much material can be removed from a factory Nitrided crank without compromising the benefits? I have read .004″ for modern process, to .30 for old GM products. I need the “Authority’s” input please.

    1. Howard, If you have to grind a nitride crank, it has to be re-nitrided. You may have put down a misprint, but .30 is a huge amount of material. If you meant .003, it is still too much for an old GM factory nitride crank. I might polish one .001 under, but if it goes .010 or .020 under, you need to re-nitride.

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