MoGas Tips, Tricks, Concerns, How To

1 The octane measurement is an attempt to quantify a fuels propensity for
detonation or pre combustion. Higher octane means less propensity.
2 Precombustion and detonation are usually caused by, among other things,
engine overheating, and hot spots.
3 Precombustion and detonation can lead to further increases in CHT.
4 Precombustion and detonation can damage an engine.
5 High CHTs can damage an engine.

Let me know which of the above statements you disagree with, and I will find
a reference for it.
I stand by my statement that an overheated engine will be more damaged if it
is running lower octane fuel.

"Jay Honeck" wrote in message
oups.com...
I also agree with posters that claim that mogas can lead to early engine
wear. The fuels may be equivalent under normal circumstances, but if the
engine overheats, the low octane fuel will do a lot more damage than the
high octane fuel.

That is simply not true. Perpetuating a myth like that in this forum
is not productive.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

Let me know which of the above statements you disagree with, and I will find
a reference for it.
I stand by my statement that an overheated engine will be more damaged if it
is running lower octane fuel.

None of your statements are incorrect, they are merely irrelevant.

Low-compression aircraft engines were designed to run on 80 octane
fuel. Running fuel of higher octane is not going to hurt anything --
but it won't help, either.

87 octane auto gas is perfect for our low compression engines, and
certainly won't hurt them. Using "premium" (or, for that matter, 100
LL) is neither necessary nor recommended.

(Note: SOME mogas STCs do require using a higher octane car gas, but
those are the exception, not the rule.)
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

If you run your car engine on 80 octane mogas, it will usually run fine. If
your car overheats, it will start to knock. If you have 100 octane gas it
will start to knock at a higher CHT than if you ran at 80 octane. This is
not usually a problem in a car that has a radiator and thermostat to
regulate the temperature.

In an airplane the same is true. Run normally both octanes are fine. In an
airplane with a manually adjusted mixture being the only temperature control
( ignoring cowl flaps) it is much easier to overheat an engine. If your CHTs
get to high, it will start to knock. With a higher octane gas it will start
to knock at higher CHTs. Therefore, if you overheat your engine, the lower
octane gas will cause more damage than the higher octane gas. Hopefully I
have drawn a clear enough line between the statements that you said were all
true and the conclusion you said was not.

"Jay Honeck" wrote in message
oups.com...
Let me know which of the above statements you disagree with, and I will
find
a reference for it.
I stand by my statement that an overheated engine will be more damaged if
it
is running lower octane fuel.

None of your statements are incorrect, they are merely irrelevant.

Low-compression aircraft engines were designed to run on 80 octane
fuel. Running fuel of higher octane is not going to hurt anything --
but it won't help, either.

87 octane auto gas is perfect for our low compression engines, and
certainly won't hurt them. Using "premium" (or, for that matter, 100
LL) is neither necessary nor recommended.

(Note: SOME mogas STCs do require using a higher octane car gas, but
those are the exception, not the rule.)
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

"soxinbox" wrote in message
...
If you run your car engine on 80 octane mogas, it will usually run fine.
If your car overheats, it will start to knock. If you have 100 octane gas
it will start to knock at a higher CHT than if you ran at 80 octane. This
is not usually a problem in a car that has a radiator and thermostat to
regulate the temperature.

I can't remember seeing anything less than 85 octane car gas since, oh,
maybe the 60's?

"Matt Barrow" wrote in message
...

"soxinbox" wrote in message
...
If you run your car engine on 80 octane mogas, it will usually run fine.
If your car overheats, it will start to knock. If you have 100 octane gas
it will start to knock at a higher CHT than if you ran at 80 octane. This
is not usually a problem in a car that has a radiator and thermostat to
regulate the temperature.

I can't remember seeing anything less than 85 octane car gas since, oh,
maybe the 60's?


Around here the grades on the pump are 83,89 and 93. Here=South & Central
Arkansas.

On Fri, 12 May 2006 08:42:59 -0500, "Gig 601XL Builder"
wrDOTgiaconaATcox.net wrote:


"Matt Barrow" wrote in message
...

"soxinbox" wrote in message
...
If you run your car engine on 80 octane mogas, it will usually run fine.
If your car overheats, it will start to knock. If you have 100 octane gas
it will start to knock at a higher CHT than if you ran at 80 octane. This
is not usually a problem in a car that has a radiator and thermostat to
regulate the temperature.

I can't remember seeing anything less than 85 octane car gas since, oh,
maybe the 60's?


Around here the grades on the pump are 83,89 and 93. Here=South & Central
Arkansas.

I've always wondered why the mogas octane levels are different around
various areas of the US. Where I live (northwest), our mogas is
87, 89 and 92.

Bela P. Havasreti

"Bela P. Havasreti" wrote in message
...
On Fri, 12 May 2006 08:42:59 -0500, "Gig 601XL Builder"
wrDOTgiaconaATcox.net wrote:


"Matt Barrow" wrote in message
...

"soxinbox" wrote in message
...
If you run your car engine on 80 octane mogas, it will usually run
fine.
If your car overheats, it will start to knock. If you have 100 octane
gas
it will start to knock at a higher CHT than if you ran at 80 octane.
This
is not usually a problem in a car that has a radiator and thermostat to
regulate the temperature.

I can't remember seeing anything less than 85 octane car gas since, oh,
maybe the 60's?


Around here the grades on the pump are 83,89 and 93. Here=South & Central
Arkansas.

I've always wondered why the mogas octane levels are different around
various areas of the US. Where I live (northwest), our mogas is
87, 89 and 92.


Altitude - higher needs more octane.

Bela P. Havasreti wrote:


Around here the grades on the pump are 83,89 and 93. Here=South & Central
Arkansas.

I think he's mistaken on the 83.



I've always wondered why the mogas octane levels are different around
various areas of the US. Where I live (northwest), our mogas is
87, 89 and 92.

The lowest octane that you find in a given area has to do with altitude.
The higher you are the less octane you need. Around here regular is 85.5

Lower octane autogas is quite common in mountain states where the
elevation is high. Non turbo-charged car engines have a bigger
denotation margin at higher elevation and require less octane.

On 12 May 2006 12:00:24 -0700, "M" wrote:

Lower octane autogas is quite common in mountain states where the
elevation is high. Non turbo-charged car engines have a bigger
denotation margin at higher elevation and require less octane.

So that's why "super" mogas in Florida is 93 octane but only
92 octane in the Seattle area. Thanks everyone for the replies
(usenet is good for something besides arguing about politics
afterall!).

Bela P. Havasreti