Based on the G100UL fuel leak thread what's your position?

[IvanP]

If the lower price will attract more buyers, it will be a boon for local paintshops in few months as the paint stripper will work its magic and planes will have to be painted  

[Slick Nick]

Listening to Braly double down on this garbage has me shaking my head. I was a fan of Mike Busch too, I know him and Braly are friends, but I was very disappointed that he seems to completely ignore the empirical data that shows how damaging G100UL is to fuel systems. It’s pretty obvious how toxic this crap is. 

[gabez]

3 hours ago, Slick Nick said:

Listening to Braly double down on this garbage has me shaking my head. I was a fan of Mike Busch too, I know him and Braly are friends, but I was very disappointed that he seems to completely ignore the empirical data that shows how damaging G100UL is to fuel systems. It’s pretty obvious how toxic this crap is. 

he is dragging mike with him 

[N201MKTurbo]

It seems that most of the other candidate fuels don’t perform as well as G100Ul. 
 

This is second hand information. There was a fuels lecture by a member of the EAGLE committee at the Southwest Aviation Maintenance Symposium. I didn’t attend that session this year. It seems that they are leaning towards a lower performance fuel that doesn’t have the compatibility issues of G100UL. These fuels would require a timing reduction in some engines.

[DonMuncy]

27 minutes ago, N201MKTurbo said:

It seems that most of the other candidate fuels don’t perform as well as G100Ul. 
 

This is second hand information. There was a fuels lecture by a member of the EAGLE committee at the Southwest Aviation Maintenance Symposium. I didn’t attend that session this year. It seems that they are leaning towards a lower performance fuel that doesn’t have the compatibility issues of G100UL. These fuels would require a timing reduction in some engines.

With a timing reduction, who do you suppose is going to do the testing and POH rewriting to make a Mooney legal to fly with reduced power.

[Slick Nick]

41 minutes ago, N201MKTurbo said:

It seems that most of the other candidate fuels don’t perform as well as G100Ul. 
 

This is second hand information. There was a fuels lecture by a member of the EAGLE committee at the Southwest Aviation Maintenance Symposium. I didn’t attend that session this year. It seems that they are leaning towards a lower performance fuel that doesn’t have the compatibility issues of G100UL. These fuels would require a timing reduction in some engines.

This is great news in my opinion. If there isn’t a suitable “drop in” fuel, the government will have no choice but to continue with leaded avgas. 

[N201MKTurbo]

14 minutes ago, DonMuncy said:

With a timing reduction, who do you suppose is going to do the testing and POH rewriting to make a Mooney legal to fly with reduced power.

I don’t know. It seems that they are trying to say that it is not enough to worry about.

[PT20J]

Depending on the amount of reduction, a timing change might not make much difference. The peak cylinder pressure and the crank angle where it occurs has a big effect on detonation margin and is very sensitive to ignition timing. However, although the power vs timing curve for internal combustion engines has a maximum, it is pretty broad. In other words, +/- 5 deg off Maximum Brake Torque timing only affects power by about 1% as I recall. I'll try to find the description of it in Heywood's Internal Combustion Engine Fundamentals.

[N201MKTurbo]

Tangent alert! 
 

The FAA has a lot of other things to worry about. Piston aircraft are a dying breed. The future is with aircraft with simplified controls. That sounds innocent, doesn’t it. When you think about it, it is a little terrifying.  They are talking about certifying aircraft for carrying paying passengers with computer controls so the users only need to program their destination and hit the go button. 
 

The FAA guy who is part of the regulation writing group said the FAA doesn’t even understand the technology, but are getting massive pressure to write regulations to support it.  
 

Us pilots are going the way of the buggy whip.

[N201MKTurbo]

1 hour ago, Slick Nick said:

This is great news in my opinion. If there isn’t a suitable “drop in” fuel, the government will have no choice but to continue with leaded avgas. 

They all know that would be the best outcome. But the people outside aviation may not allow it.

[PT20J]

2 hours ago, PT20J said:

Depending on the amount of reduction, a timing change might not make much difference. The peak cylinder pressure and the crank angle where it occurs has a big effect on detonation margin and is very sensitive to ignition timing. However, although the power vs timing curve for internal combustion engines has a maximum, it is pretty broad. In other words, +/- 5 deg off Maximum Brake Torque timing only affects power by about 1% as I recall. I'll try to find the description of it in Heywood's Internal Combustion Engine Fundamentals.

Here's the reference: Heywood - Spark Timing_20260330_0001.pdf

[hazek]

I emailed Lycoming about this. I asked what can I as an owner of TIO-540-AF1B expect here and if they had a plan. The guy wrote back:

"Thank you for contacting Lycoming. Lycoming is very much aware of the FAA’s plans and is a key member of the EAGLE Initiative in providing input to help this transition. Lycoming does indeed have a plan to address engines such as the TIO-540-AF1B, but I am unfortunately unable to say more at this time."

I wonder what Cirrus is up to. One would think the biggest market players have way more on the line here than us mere owner/operators. Is Cirrus just going to let down their entire fleet of SR22Ts and stop making those? Piston GA may be dying a slow death, but they still make a bil per year selling those, no?

It seems like by the end of this year we'll know what the future holds. I sure hope so because I hate to be in this limbo of not knowing. Makes me almost want to put mine up for sale and start saving for a DA42-62.

[Justin Schmidt]

7 hours ago, hazek said:

I emailed Lycoming about this. I asked what can I as an owner of TIO-540-AF1B expect here and if they had a plan. The guy wrote back:

"Thank you for contacting Lycoming. Lycoming is very much aware of the FAA’s plans and is a key member of the EAGLE Initiative in providing input to help this transition. Lycoming does indeed have a plan to address engines such as the TIO-540-AF1B, but I am unfortunately unable to say more at this time."

I wonder what Cirrus is up to. One would think the biggest market players have way more on the line here than us mere owner/operators. Is Cirrus just going to let down their entire fleet of SR22Ts and stop making those? Piston GA may be dying a slow death, but they still make a bil per year selling those, no?

It seems like by the end of this year we'll know what the future holds. I sure hope so because I hate to be in this limbo of not knowing. Makes me almost want to put mine up for sale and start saving for a DA42-62.

We can't tell you what we are doing until everyone is forced to follow what other morons prescribe.

[IvanP]

7 hours ago, hazek said:

I emailed Lycoming about this. I asked what can I as an owner of TIO-540-AF1B expect here and if they had a plan. The guy wrote back:

"Thank you for contacting Lycoming. Lycoming is very much aware of the FAA’s plans and is a key member of the EAGLE Initiative in providing input to help this transition. Lycoming does indeed have a plan to address engines such as the TIO-540-AF1B, but I am unfortunately unable to say more at this time."

Translated from lawyer speak to plain English: We are scrambling and have no f-ing clue of what comes next. 

[Paul Thomas]

On 3/30/2026 at 11:01 PM, PT20J said:

Depending on the amount of reduction, a timing change might not make much difference. The peak cylinder pressure and the crank angle where it occurs has a big effect on detonation margin and is very sensitive to ignition timing. However, although the power vs timing curve for internal combustion engines has a maximum, it is pretty broad. In other words, +/- 5 deg off Maximum Brake Torque timing only affects power by about 1% as I recall. I'll try to find the description of it in Heywood's Internal Combustion Engine Fundamentals.

I read 3* but it would have no effect on power due to the change in fuel.