There is less than zero chance that 100LL is going “without too much prior notice” in the US.
There are 3007 counties in the US. One of them, in a notably wacko left-wing activist part of the US, is using this issue as a tactic to force closure of two of approximately 20,000 US airports, 5200 of them being public use airports. FAA is now investigating. This is not synonymous with the demise of 100LL 
Silvaire wrote:
in a notably wacko left-wing activist part of the US
You left out one important word: corrupt. Otherwise 100% agree.
Silvaire wrote:
There is less than zero chance that 100LL is going “without too much prior notice” in the US.
The one way I could see something like that is if federal politics slide off the left hand edge and those people want to be seen “doing something” which pisses off the least amount of voters but has a huge symbolic impact.
But whatever the likelyhood, why not work in that direction anyway? Leaded fuel is not a good thing, it’s expensive, it has issues and it would help the image of GA worldwide if we finally could get to the point where all airplanes fly without led. Why wait until the rug is pulled from under us?
The advantage Diesel has over any new found UL fuel is that it exists, is certified and available. That is the main reason why diesel engines could succeed, as they do in Europe. But if the efforts of replacing Avgas LL with a UL fuel which can run the engines which keep Avgas 100LL alive, so much the better.
100LL is currently very slightly cheaper than premium auto fuel in my area, at $4.55/USG or Euro 1.05/liter. It is not particularly expensive, although I’d prefer to pay less, its widely available in the US and will remain so until another competitive fuel arrives someday. Environmental symbolism is a lesser concern for most in the US than you may expect, especially when it costs very real money for middle class people.
It appears to me Diesel aero engines will likely never succeed in the US. Its conceivable that they could succeed, someday, but the infrastructure for and practicality of owning an existing Avgas engine is way better for most people, and the associated costs are much lower. The only niche that Diesels can attempt to fill is very high utilization (e.g. fleet) service where a small reduction in fuel price can make a difference to the bottom line. Most GA owners/buyers of e.g. a new Cirrus are not operating a fleet or flying a huge amount and more pilots in the US are aircraft owners, not renters who aren’t writing the big checks and like environment symbolism. A change in that position would take an inconceivable tax penalty to be applied to US operators of Avgas engines, creating a new, artificial tax-driven marketplace. That’s not very likely to happen, even if e.g. military funding from UAV development continues to produce more and larger Diesels at lower cost, that could be used for GA aircraft too.
Why is 100LL cheaper than auto fuel in the US?
Commercially that doesn’t make sense based on usage,I would have thought plus the extra cost of refining. Is auto fuel taxed more than 100LL?
Yes, relatively high state and local taxes on auto fuel, in my area. Plus relatively high volume 100LL sales by retailers in my area, with competition between multiple vendors and airports.
gallois wrote:
Why is 100LL cheaper than auto fuel in the US?
It isn’t. That said, the prices are very close right now. @Silvaire’s figure is an outlier, around here (coastal SoCal) it’s hovering around $ 5.00 give or take. At my home airports it’s $5.51 and $ 5.95 (ouch!) respectively.
Average car gas in CA (important distinction – most expensive in the US!) is 4.65 for regular, $4.97 for premium. I don’t know anyone who uses the latter, so prob90 also not a huge sales volume.
PS to add: if you want to see 100LL and Jet-A prices for yourself, see here.
I just checked on line… I’m paying $4.55/gallon for 100LL, $4.09 for regular car fuel, and $4.41 for premium (I have one car that uses it, but not often).
So premium auto fuel available to me today is actually 3% less than 100LL, not slightly more as I said. The prices change daily. Also, as mentioned auto fuel in other parts of the US is 25% less due to local tax differences.
That’s interesting. Where I am in France at the moment prices of all fuel has risen over the last month or 2. Motor fuel tends to rise and fall during the course of a week whereas the price of 100LL stays stable, because of lack of turnover.
At present 100LL is around €2.20 per litre (over €8 a gallon) unleaded is €1,50 a litre (€5,80 per gallon) diesel is a little cheaper than unleaded but not much and jet A a little cheaper again, but again not by much. I write here of man in the street prices not of companies who can reclaim VAT etc.
Most ULMs, and kit planes use unleaded here
Orphelins, experimentals and collection aircraft are of course split in the same way as certified a/c as to the type of fuel they use.
There is a small outfit at Brest which sells a kit plane which can be built in their workshops which has a PSA engine I believe the same as found in a Peugeot 106 and I believe it did Brest ,-Corsica -Brest on less than €100 of diesel.
Fuel is irrelevant to this topic, surely.
To get this back on the topic: is the 9kt gain real? That is a LOT of HP “gained”. If it was obtained via extra HP, it would be some tens of HP.
