The staggering chicken test

In response to a previous column in which I expounded on the problem of exhaust valve recession with unleaded fuels, I received a note from Ron Newberg, which reminded me of work done by the oil companies back in the early 1970s. I actually ran some of these tests, in which we demonstrated that Tri-Cresyl Phosphorous (TCP) added to an unleaded fuel reduces the amount of exhaust valve recession. It worked well. Since TCP is approved for almost all aircraft piston engines, it is an immediate approved solution for the exhaust valve recession problem. But, alas, nothing is that simple. TCP will work, but it has some health concerns.

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Our fuels expert visits Swift Fuels


Swift Fuels has been working on a 100 octane unleaded avgas for a number of years. I have been, shall we say, less than enthusiastic about the company’s work for various reasons.

However, as of late, the company seems to be making some real progress, so I drove down to Indiana to visit its facility. I am happy to report that although Swift is not “out of the woods” yet, it is making some significant progress.

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Ethanol: It will get you coming and going

Recently, reader Frank Klein asked if he should be concerned about filling up containers of auto gas for his plane if the previous customer pumped 10% ethanol fuel from a pump island that uses a common dispensing hose for several grades of auto gas.

When I do some rough calculations, I figure that the amount of fuel contained in the hose and meter would give you close to a gallon of fuel, so if you are using a five-gallon container, you would have close to 20% ethanol-containing fuel.

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Correction: Exxon Mobil to remain 100LL manufacturer

In a blog posted on Monday, December 19, fuels expert Ben Visser incorrectly stated that Exxon Mobil had stopped manufacturing 100LL for the general aviation marketplace. In fact, Exxon Mobil continues to manufacture 100LL for distribution under brand names other than its own. Exxon Mobil will cease selling 100LL under Avitat-branded FBOs. Says Ben Visser, “Sorry if I misled anyone.”

Oil giant pulls out of 100LL business

UPDATE: Calls from AOPA and EAA Tuesday morning inform us Ben’s column is incorrect. Exxon-Mobil will continue the manufacture of unbranded 100LL fuel. Exxon-Mobil will discontinue branded fuel sales under the Exxon Avitat flag. We are awaiting confirmation from Exxon’s public relations people.

I recently read that Exxon-Mobil stopped manufacturing and selling 100LL. (I tried to contact them but did not receive a confirmation by press time.) What does this mean for you and your plane?

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What part of ‘no’ don’t they understand?

One of the joys of being retired is that I get to read more of the newspaper each evening. Now the front page has all of the big stories that are of worldwide importance, like the Kim Kardashian marriage that lasted only 72 days. But if you read the inside pages, you can find some very interesting information. On page 5 of our local daily paper here in the agriculture heartland was an article that caught my eye. The headline read: “Study: E15 damages boat engines.”

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Why lead reduces knock

In the Sept. 23, issue of General Aviation News, there was a letter to the editor from Jack Thompson, who wrote: “Re: Visser’s Voice: Knock free, Aug 26 issue: It is a sad commentary given that the IC engine is such an integral part of aviation that the user community is so ignorant of its operation and engineering issues. What percentage of the users understand the impact of fuel detonation resistance and the if-then relationships of fuel suitability for a given service?”

The actual truth is that no one really completely understands the interaction, especially how lead additives work in a fuel to reduce knock.

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Winterizing your plane

A couple of days ago when I went out for my morning walk I noticed something had changed. Instead of warm and sunny, there was a chill in the air. I then realized that fall is approaching and I needed a jacket.

The same kind of thing happens to many pilots each year. They are enjoying the nice flying weather when all of a sudden, winter is upon them, so they put their plane away and figure they will just change the oil in the spring before they do any more flying. There is a big problem with this plan.

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Knock free

In one of my recent columns I stated that if an engine runs knock free on an 87 octane fuel, using a higher octane fuel will not benefit you in any way. I received several inquiries about whether this was for automobiles or airplanes. Basically it applies to both.

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Flawed logic

Ben Visser is an aviation fuels and lubricants expert who spent 33 years with Shell Oil.

I recently received a question from reader Bill Blank asking whether there was more BTUs in higher octane fuels and if there was any reason to use a higher octane fuel if a vehicle ran knock free on a lower octane fuel. The simple answer is no.

I have received this question many times and the concept of more is always better is very ingrained in our minds. [Read more…]