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Continental IO-360-AF - a joke?

Continental is making a big fuss about that engine having received approval to run on…… UL91!

Isn’t that a bad joke? I mean, Continental has been known for being way behind on UL91 certifications, so they might honestly consider it a milestone. But other than that, UL91 is still very rare in Europe and usually costs the same as 100LL.

A useful thing would be mogas95 approval, which is quite a bit more common at airfields in some european countries. But that seems almost impossible to get approval for these days.

Mainz (EDFZ), Germany

What is the verdict on 91UL, after all this time?

It does seem like a failed market-push experiment by TOTAL, who tried all they could to get airfields to drop 100LL.

Shoreham EGKA, United Kingdom

It does seem like a failed market-push experiment by TOTAL

In the UK maybe. Things are different elsewhere. The thing is, price has nothing to do with it. You cannot make UL91 cheaper than 100LL, so unless the authorities forbid 100LL or put heavy taxes on it, everybody will continue to be happy with the current situation and fill up with 100LL.

UL91 is the correct fuel for 95% of todays fleet. Include microlight/LSA/VLA and it is the correct fuel for 99.9% of the fleet. Mogas is not aviation fuel.


“his further demonstrates Continental’s reputation for delivering innovative products that are backed by an experienced staff and a 100-year history”

Innovative 100-year old products is what he meant.

You cannot make UL91 cheaper than 100LL

That can’t be actually correct because 100LL contains TEL which

  • costs a bit of money (not much)
  • demands separate handling methods to avoid contamination
  • demands “decontamination” of any plant used to handle it before the said plant can be used for unleaded fuel
  • has “environmental resistance” from all the usual fashionable quarters

Your statement could of course be true if the volume on 91UL is lower, which it must be because 91UL cannot possibly capture 100% of the 100LL market.

But then one could say that about any fuel whose mfg volume is less than 100LL. If the volume goes low enough, the costs will be arbitrarily high.

95% of todays fleet.

Maybe 95% of a pre-selected fleet i.e. microlight/LSA/VLA. No way is it 95% of the avgas sales by airports – because the biggest fuel buyers are people with engines which are not certified for 91UL. In the USA, I recall seeing a figure of 2/3 of total avgas (100LL) sales going into turbocharged engines which are mostly uncertified for 91UL (they do actually run fine on it but that’s another argument).

In Europe this will be less… not many of the “out and out” 100LL burners are doing many hours (a 421C could easily burn 20-30 tons of 100LL in a year, just on noncommercial GA usage, but most of them aren’t really flying; one in “my” hangar was doing 4hrs/year). But it will still be substantial and if you add in the bigger landing fees paid by those planes, no way is an airport going to carry 91UL if it makes 100LL even slightly less economical.

One UK airport manager said openly that about 10% of his avgas sales were 91UL. He pushed 91UL pretty hard (got a free bowser from TOTAL too) but… That of course is not the same thing as saying that only 10% of his avgas customers could use 91UL. The truth will be somewhere in between; probably 50%. He has a number of SR22Ts hanging out there.

Shoreham EGKA, United Kingdom

Mogas is not aviation fuel.

Well, that is just about the weakest argument I’ve ever seen…

Well, that is just about the weakest argument I’ve ever seen…

But that is also the reason quoted by Lelystad Airport for stopping sales of MOGAS as of 1st April – when the fuel contract is transferred from BP to TOTAL who are busy right now installing tanks for UL91. Only clubs, rental companies will now be able to tank MOGAS at EHLE but they will have to provide their own tank installation or bowser and will not be permitted to sell it to third parties.

EHLE / Lelystad, Netherlands, Netherlands

The truth will be somewhere in between; probably 50%.

From a technical/engineering point of view this is completely off the scale in terms of stupidity. Any engine can be modified to run UL91. The only thing needed is to lower the CR. Worst case scenario is you lose 3-4% max power. The truth is, this is a bureaucratic problem (certifications, regulations) that has no cost effective bureaucratic solution because there is no political will to solve it. There is no political will because the problem itself is microscopic in a global scale, and it’s better just to let things run its course and let diesel and UL91 take over more and more until the lack of demand for 100LL makes it disappear by itself.

Well, that is just about the weakest argument I’ve ever seen…

I know, but it’s the truth nonetheless. UL91 is so much better in so many ways than mogas.

What is the MOGAS composition control and quality control like, compared to 91UL?

Shoreham EGKA, United Kingdom

My Warrior flies on MoGas from 2002. There have never been ANY problems. In contrary the spark plugs stay clean now, no more problems at runup (which were normal for that plane from 1978-2002). Also it was flown at FL100-130 a lot, still no problems.

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