2024 the year of GAMI - finally?

[Pinecone]

I change my own oil. Cost of oil and filter is half of what you mentioned. That's not enough (cost-wise) to make me switch. And as OCT mentioned above, if the extra $1 is their production cost, not price at the pump, then the math becomes even more unfavorable for them.

At that point, we ethanol-proof our fuel systems, figure out a safe additive to handle water in fuel (I hear some people mention isopropyl alcohol?) and we convince airport managers to fill their tanks with mogas instead.

Then there is that your spark plugs will last longer.

And it is likely the engine will last longer. And even more so if we can get some synthetic oils.

In dino oil days, auto engines were good for about 100,000 miles. Now they do 250K or more. How about skipping even just one overhaul?

Funny thing about fuel prices, when I was flying before my hiatus, everyone was squawking about the demise of GA if AVGAS prices went over $4 per gallon. And you could still find fuel for under $2 per gallon. Now the sky is falling if we hit $10. Will some people stop flying? Sure. But even if fuel prices don't go up, a number of people will stop flying.

 

[schmookeeg]

Funny thing about fuel prices, when I was flying before my hiatus, everyone was squawking about the demise of GA if AVGAS prices went over $4 per gallon. And you could still find fuel for under $2 per gallon. Now the sky is falling if we hit $10. Will some people stop flying? Sure. But even if fuel prices don't go up, a number of people will stop flying.

My favorite bit of this is the people I talk to "waiting for prices to go back down" before they buy an airplane, when I'm pretty confident the current price regime is "the new normal" and people need to adjust their expectations. Particularly for blue-chip planes like 182s and bonanzas. Some of the fringe high-opEx stuff that has run up recently may retrench a bit, but certainly not all the way to how it was 5 years ago.

 

[AV8R_87]

The range of inconsistency in automotive pump gasoline is extreme, and the type of fuel you get in different locations can be massively different, based on differences between supplier, local blend regulations, and a whole lot of other stuff.

While there are differences between summer and winter blends, and altitude adjustments, these are pretty well documented in federal fuel standards. Not to the level of AVGAS, I agree. But it's not as unreliable as you make it sound.

And an airport manager could specify a particular blend, that is suitable for high altitude operation and without all the butane blended in that lowers the vapor pressure.

And all those blends run just fine in my air-cooled, 8:1 compression ratio, fixed ignition timing cheap generator, that can generate 7 hp from 13 cubic inches (at 3600 rpm). That's comparable to the output of the typical air-cooled airplane engine.

I have zero interest in trusting my life to it.

Sadly, we might not have a choice if we want to keep flying.

Waiting to hear how you plan to address that vapor pressure problem with some low-wings....

Keep the tank pressure above vapor pressure. Or at least the pressure in the fuel lines. At some point, the cost of two in-tank fuel pumps will be more than offset by the lower fuel costs.

 

[Pinecone]

Although the consistency of AVGAS is not perfect. I was talking to the Cies president at a Mooney gathering and asked why we can't have accurate capacitive fuel gauges like the turbine guys with no moving parts.

He told me they tried it, but the capacitance of AVGAS varies too much.

 

[AV8R_87]

Surprised to hear that. Turbines can usually handle multiple grades of jet fuel, and you never see mentions in the TCDS about fuel quantity inaccuracies when using different fuels.
I wonder if the problem might be caused by some anti-static additives that might be included in the avgas. I could see those messing with the fuel conductivity in ways that might get unpredictable.

EDIT:
Anything is better than most resistive-based fuel probes we have in GA today. With today's technology I think there could be better ways to measure fuel levels in the tanks (even better than capacitive probes), but that sounds to me more like stuff to write in a patent application and not in a public forum.

 

[Pinecone]

Anything is better than most resistive-based fuel probes we have in GA today. With today's technology I think there could be better ways to measure fuel levels in the tanks (even better than capacitive probes), but that sounds to me more like stuff to write in a patent application and not in a public forum.

Cies has them

 

[Tusayan]

And all those blends run just fine in my air-cooled, 8:1 compression ratio, fixed ignition timing cheap generator, that can generate 7 hp from 13 cubic inches (at 3600 rpm). That's comparable to the output of the typical air-cooled airplane engine.

But not comparable in terms of the required octane. That is a function of cylinder bore, as well as CR, RPM and ignition/cam timing. Large displacement cylinders need more octane, with everything else held constant.

 

[AV8R_87]

Not really. The 7:1 O-320 was certified to run on 80/87 Avgas and has auto fuel STCs approving it to run on regular (AKI 87, MON 82) gasoline. The 8.5:1 O-320 requires 91/96 Avgas and the auto fuel STC approves it to run premium (AKI 91, MON 88). Similar situation for the O-540, but I haven't looked at all the different variants there.
I'd say that's pretty comparable.

I think (please correct me, my knowledge is definitely limited here) 100LL is needed mainly for the turbocharged models. A lot of the engines "requiring" 100LL only do that because at the time the airframe/powerplant combination was certified, 100LL was the only fuel available. Nobody will issue a TCDS for fuels that haven't existed in decades.

 

[Racerx]

Not really. The 7:1 O-320 was certified to run on 80/87 Avgas and has auto fuel STCs approving it to run on regular (AKI 87, MON 82) gasoline. The 8.5:1 O-320 requires 91/96 Avgas and the auto fuel STC approves it to run premium (AKI 91, MON 88). Similar situation for the O-540, but I haven't looked at all the different variants there.
I'd say that's pretty comparable.

I think (please correct me, my knowledge is definitely limited here) 100LL is needed mainly for the turbocharged models. A lot of the engines "requiring" 100LL only do that because at the time the airframe/powerplant combination was certified, 100LL was the only fuel available. Nobody will issue a TCDS for fuels that haven't existed in decades.

1967 NA Cherokee six requires aviation grade 100/130 for the io-540-k1a5.

 

[Jim K]

I think (please correct me, my knowledge is definitely limited here) 100LL is needed mainly for the turbocharged models. A lot of the engines "requiring" 100LL only do that because at the time the airframe/powerplant combination was certified, 100LL was the only fuel available.

My io540 requires 100ll and has since 1976. 8.7:1. The only 540 that has a mogas stc is the 235hp version.

It's much more complicated than compression ratio, it really has to do with peak pressures in the cylinder (which have a lot to do with airflow). An IO-540-C4B5 vs. an IO-540-K are great examples. 8.5 and 8.7:1 compression (respectively), however the -C4B5 will use MoGas just fine, and the -K will not. Difference? The parallel valve cylinders on the -C4B5 flow much less air than the angle valve cylinders on the -K.

Ignition timing comes into play as well and there are all sorts of things that can be changed to impact things. You need to look at the engine as a complete system, not just one part of it.

Basically any angle valve lycoming requires 100ll. That's the io360 & io540. The big continentals that power the bonanza and cirrus fleet also require 100ll. Eliminating 100 octane fuel grounds pretty much anything other than the c172/pa28 fleet.

 

[Ted]

Basically any angle valve lycoming requires 100ll. That's the io360 & io540. The big continentals that power the bonanza and cirrus fleet also require 100ll. Eliminating 100 octane fuel grounds pretty much anything other than the c172/pa28 fleet.

Correction: angle valve 360/540s. There are plenty of IO-350/540s that are parallel valve, and those don’t require 100LL.

The valve arrangement only matters because angle valves flow more and make more horsepower.

 

[tspear]

In terms of lead, there is a source for a lot of the benefits which could be seen. From my limited knowledge, it mostly applies to new or overhauled engines.
Look at Rotax. They provide the information when running mogas vs avgas.

Tim