Swift 100R is now ASTM

[Ibra]

54 minutes ago, Ryan ORL said:

From what I've read about it thus far, its MON is lower than 100LL and G100UL (neither of which are actually 100 in reality, but higher), which would significantly reduce detonation margins in my engine (IO-360-A3B6) for example

I don't think Swift will struggle with 100R in IO360-A3B6? we will know soon for sure.

I recall at Oshkosh this year, they mentioned 1000 engines being tested for 100R. However, they admitted challenges for Conti 550 and Lyco 540, for these engine, G100UL is probably the only choice for now...

Recently, Lycoming has proved that TIO540-J can run on 96 MON octane with adjusted pressure-timing, so even Swift 100R fuel can get their way into these, here is the fun part, these engine may need to use GAMI PRISM or TCM PowerLink, these need to be certified, things could be heading that way as well, if the price of these magnetos is right...

 

 

Edited Friday at 09:22 PM by Ibra

[Joshua Blackh4t]

If Gami fuel is better for the engine, but harder on the tanks and paint, I think I'd wear that risk. Maybe use better paint around the filler area? It could be a feature, especially not an issue on high wings. 

If the cost of continuing to fly our planes is new fuel lines, maybe a tank reseal and some industrial paint around the filler, well, then so be it. Better than the alternative. 

[toto]

I went around looking for some first-hand experiences with 100R. 

This thread has some mildly interesting feedback, including the apparent fact that the Swift fuel uses no aromatics (which I guess is the source of most of the materials incompatibility issues with G100UL).

https://old.reddit.com/r/flying/comments/1h3zdfy/100r_smells_weird/

At this point, “different from G100UL” seems like a key measure of success. Both for certification and formulation.  

[Will.iam]

I thought I remember in one of gami's engine test, that no detonation happens until CHT gets above 420 degrees even if you run the engine right at the worst possible red box area but the rate at which the CHT's are rising is fastest there.  Seems to me if we now have good CHT monitors, and most consider 400 degrees the upper limit, that if 100R did not have as much detonation margin, you would see it on take off if you had a cht rising above 400. question would be if reducing power would be acceptable enough to still make the climb out profile?

[0TreeLemur]

9 hours ago, Will.iam said:

question would be if reducing power would be acceptable enough to still make the climb out profile?

That is an excellent question.   If yes, then the question becomes are you willing to live with a reduced margin of safety on CHT that prevents your engine from self destructing?

[Rick Junkin]

15 minutes ago, 0TreeLemur said:

That is an excellent question.   If yes, then the question becomes are you willing to live with a reduced margin of safety on CHT that prevents your engine from 

Is a demonstrated full power detonation margin a requirement for approval of a fuel for use in a given engine/aircraft? In other words, is it even possible that reducing power would be an option available to us?

I don’t know anything about how this approval process works, either by STC or ASTM. Someone much smarter than me please weigh in. Could a fuel be approved and available for use in a given engine if that fuel/engine combination wasn’t able to demonstrate some nominal full power detonation margin?

[gabez]

On 9/5/2025 at 2:58 PM, Joshua Blackh4t said:

If Gami fuel is better for the engine, but harder on the tanks and paint, I think I'd wear that risk. Maybe use better paint around the filler area? It could be a feature, especially not an issue on high wings. 

If the cost of continuing to fly our planes is new fuel lines, maybe a tank reseal and some industrial paint around the filler, well, then so be it. Better than the alternative. 

unfortunately you do not know what needs to be done to your plane to be fully compatible with G100UL. Braly won'd disclose the log books from his Cirrus. Every plane that uses G100UL is a guinea plug. It's not just lines and paint. 

[1980Mooney]

11 hours ago, gabez said:

unfortunately you do not know what needs to be done to your plane to be fully compatible with G100UL. Braly won'd disclose the log books from his Cirrus. Every plane that uses G100UL is a guinea plug. It's not just lines and paint. 

Every plane that uses Swift fuel is a guinea pig.

Swift 94UL met ASTM D7547.  Yet prolonged use by UND caused documented engine damage.  UND Report Details Valve Issues Experienced With Swift Fuels 94UL - AVweb

And Swift already admits that there are issues with 100R in high performance engines - big 6's and turbocharged.  

[1980Mooney]

13 hours ago, Rick Junkin said:

Is a demonstrated full power detonation margin a requirement for approval of a fuel for use in a given engine/aircraft? In other words, is it even possible that reducing power would be an option available to us?

I don’t know anything about how this approval process works, either by STC or ASTM. Someone much smarter than me please weigh in. Could a fuel be approved and available for use in a given engine if that fuel/engine combination wasn’t able to demonstrate some nominal full power detonation margin?

I don't see how that could work.  That solution means a pilot would need to reduce power just when he likely needs full power.  For those of us back in the 60's and early 70's that used to experiment with distributor timing finding maximum spark advance on our manual transmission cars, when we heard it knocking, we could just let off the throttle or maybe downshift before going into full blown detonation.   We could just pull over and stop - maybe fiddle with the timing advance some more.

 But with our plane, there are many times we need full power - take off, clearing an obstacle.  That means the POH would need two (2) sets of performance charts/sections for Full Power and Reduced (Knocking/Detonation) Power.  Putting a pilot in the position of trying to decide whether to destroy the engine vs attain a needed rate of climb seems like a formula for disaster.  I bet the lawyers for everyone (airframe, engine and even the fuel suppliers) would stop it in its tracks.

More likely they would mandate permanent engine modifications such as reduced compression (piston change), reduced timing, reduced max RPM, limited/reduced max boost

[gabez]

3 hours ago, 1980Mooney said:

Every plane that uses Swift fuel is a guinea pig.

Swift 94UL met ASTM D7547.  Yet prolonged use by UND caused documented engine damage.  UND Report Details Valve Issues Experienced With Swift Fuels 94UL - AVweb

And Swift already admits that there are issues with 100R in high performance engines - big 6's and turbocharged.  

I appreciate that. I don't mind knowing there are issues with certain engines, I do mind when GAMI comes out saying it is drop in and then 25+ planes got bricked and one was totaled $600K 421C. 

They now have changed their narrative: as there is no perfect fuel, they have added a disclaimer on wet tanks when you buy the STC and changed the FAQ. in November when I (and many others) got the STC it was drop in, don't need to change a thing. and that's a fact. 

[Ibra]

13 hours ago, 1980Mooney said:

I don't see how that could work.  That solution means a pilot would need to reduce power just when he likely needs full power.

The problem with UND was not "full power (rich climb)", it was their "leaning technique (cruise)".

In UND, they were running Archers at 70%-80% power on peak EGT with CTH > 450F as "normal business", I get that Lycoming engines are certified by FAA to cope with continuous max power and max CHT = 500F on 100LL, however, only a monkey flies like that (most of us tend to babysit the engine).

I have operate the Archer that UND flew, albeit on less hours (450h over 5 years), I flew it using SP98 (87 Octane) on Mogas STC, takeoff were never a problem and I never let CHT > 390F in climbs or cruise:

* Patterson STC, prohibited peak EGT operation on Mogas EN228.

* Lycoming advise against peak EGT operations at 75% on Avgas 100LL.

Basically, they were "red-boxing" even with 100LL, it's not advisable and it's false fuel economy. Most schools tend to have various SOP to keep CHT under 400F, use 55%-65% power? keep full rich? 

I think on gently engine management, I am sure one can make sacrifices but for airframe, fuel tanks, paint...there is not much one can do...

If 100R is fine for airframe, I am fine using it even with bunch of placards on leaning or CHT 

Edited 8 hours ago by Ibra

[Ibra]

On 9/6/2025 at 6:18 PM, Will.iam said:

I thought I remember in one of gami's engine test, that no detonation happens until CHT gets above 420 degrees even if you run the engine right at the worst possible red box area but the rate at which the CHT's are rising is fastest there.  Seems to me if we now have good CHT monitors, and most consider 400 degrees the upper limit, that if 100R did not have as much detonation margin, you would see it on take off if you had a cht rising above 400. question would be if reducing power would be acceptable enough to still make the climb out profile?

I am sure most of us don't exceed CHT > 420F on takeoff? in M20J, you need to climb at VX with cowl flap closed to 2000ft with OAT at 100F, assuming one is full rich (they need to be at least 250F - 350F Rich of Peak to keep out of "red-box").

Most of us already accept lower climb gradients as we tend to "baby sit" engines under 390F on climb by using more speed or more fuel to keep out of red-box, same when we lean LOP under 65% power, it's not optimal but that's how one keep their engines running for a long time.

I don't feel that I compromise any safety for keeping CHT < 400F even while using 100LL: I can still fly where I want with no apparent limitations, well I use full rich for takeoff (unless high density), I  climb at Vy to cool my engine and I tend to LOP under 65% power. I would do the same with 100R, 

Of course there are pilots who can melt an IO360 by aggressive leaning toward peak EGT at 100%-75% power, having 100LL or 100R, won't change anything for such pilot...

Edited 18 hours ago by Ibra

[McMooney]

at some point, lycoming or mooney tested 96 octane fuel,  in my lycoming io-360-a1a and found it acceptable, so pfft don't care at all about some 1000hp engine not being able to use it. 

 where is this blurb 100r may not work in some applications?  heck i live in houston if have to reduce takeoff to 1000 fpm to prevent detonation, not seeing an issue,  anyone living higher than sea level probably wouldn't have to do anything

[1980Mooney]

2 hours ago, gabez said:

I appreciate that. I don't mind knowing there are issues with certain engines, I do mind when GAMI comes out saying it is drop in and then 25+ planes got bricked and one was totaled $600K 421C. 

They now have changed their narrative: as there is no perfect fuel, they have added a disclaimer on wet tanks when you buy the STC and changed the FAQ. in November when I (and many others) got the STC it was drop in, don't need to change a thing. and that's a fact. 

Swift said 94UL was an ASTM approved "drop-in" fuel.  Except it wasn't in the real world.  Now they say 100R is an ASTM approved "drop in" fuel.  Except it may not work in 25% of the fleet.....  "and that's a fact".

"The remaining 25% are more complicated. About 60% of that slice of the pie chart are what he calls “the 550s,” six-cylinder engines in singles and light twins that fill the gap between the engines that are quite happy on 94 UL and the ultra-high-performance boosted sixes that will be the toughest to fuel with unleaded. Testing will begin later this year on a Continental 550 and d’Acosta said it will take about 18 months."

What good is ASTM if they don't even know if it will work reliably in the Continental and big Lycoming engines? - I mean Seriously?

Edited 17 hours ago by 1980Mooney

[gabez]

2 hours ago, 1980Mooney said:

Swift said 94UL was an ASTM approved "drop-in" fuel.  Except it wasn't in the real world.  Now they say 100R is an ASTM approved "drop in" fuel.  Except it may not work in 25% of the fleet.....  "and that's a fact".

"The remaining 25% are more complicated. About 60% of that slice of the pie chart are what he calls “the 550s,” six-cylinder engines in singles and light twins that fill the gap between the engines that are quite happy on 94 UL and the ultra-high-performance boosted sixes that will be the toughest to fuel with unleaded. Testing will begin later this year on a Continental 550 and d’Acosta said it will take about 18 months."

What good is ASTM if they don't even know if it will work reliably in the Continental and big Lycoming engines? - I mean Seriously?

how many planes as UL94 totaled? 

[Pinecone]

On 9/5/2025 at 10:56 AM, EricJ said:

The benefit of a consensus standard like ASTM is that it has had eyes on it and approval by a very broad set of stakeholders, including engine and airframe manufacturers, refiners, distributors, etc., etc.  The result is that the likelihood of post-deployment issues goes way, way down. 

This contrasts significantly to the STC process where one guy can do all those functions including being the DER for the FAA.

In what way?

All an ASTM standard means is that you got a bunch of people to agree to make a standard for THAT mix.  It does not address the suitability of THAT mix to the desired use.

Swift still has not changed their stance that the fuel is NOT suitable for a good proportion of the piston fleet.