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Mogas in IO-540

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jesse(at)saintaviation.co
Guest

Posted: Tue Sep 06, 2011 2:49 pm Post subject: Mogas in IO-540

I've done a little searching on the topic, but can't find any recent articles.  What are the issues keeping someone from running mogas in a 260HP IO-540?  What I have found so far is the following problems that people mention, but not sure if the possible solutions are acceptable or accurate, and don't know details.  Also, is mixing 50/50 or something like this acceptable?  I'm just researching for possible options if 100LL is not available in a pinch.



1.	Problem: Ethanol can ruin seals in the system - Solution: Use mogas without ethanol?

2.	Problem: Detonation - Solution: Run only up to certain power settings?  Run only rich of peak?  Other?

3.	Problem: Vapor Lock - Solution: Stay below certain altitude?  Other?



do not archive



Jesse Saint

Saint Aviation, Inc.

jesse(at)saintaviation.com

C: 352-427-0285

F: 815-377-3694

Kelly McMullen

Joined: 16 Apr 2008
Posts: 1188
Location: Sun Lakes AZ

Posted: Tue Sep 06, 2011 3:25 pm Post subject: Mogas in IO-540

Item 1. You are correct.

Item 2. Do not use any mogas with less than 91 pump octane rating, and

try for 92 or 93. The engine was certified on 91/96 octane

avgas...which is a bit different scale.

Item 3. I don't know FL mogas vapor pressures. In Aridzona during the

summer it is 7.0, same as avgas, might be a couple points higher in

winter. More of a problem in summer at OSH if you got some fuel sold 6

months prior with RVP up around 12 or 14. One way to mitigate is to

run pure avgas in one tank and mogas in the other. Use Avgas for

takeoff and landing, mogas for cruising. Mixing the two fuels will

improve stability and octane of the mogas. However, you don't want

mogas to sit more than a month or so, as varnish and gum will form and

cause problems in the fuel system. Stabil additive can help.

On Tue, Sep 6, 2011 at 3:46 PM, Jesse Saint <jesse(at)saintaviation.com> wrote:

 	  Quote: 	
		   



 I've done a little searching on the topic, but can't find any recent articles.  What are the issues keeping someone from running mogas in a 260HP IO-540?  What I have found so far is the following problems that people mention, but not sure if the possible solutions are acceptable or accurate, and don't know details.  Also, is mixing 50/50 or something like this acceptable?  I'm just researching for possible options if 100LL is not available in a pinch.



 1.      Problem: Ethanol can ruin seals in the system - Solution: Use mogas without ethanol?

 2.      Problem: Detonation - Solution: Run only up to certain power settings?  Run only rich of peak?  Other?

 3.      Problem: Vapor Lock - Solution: Stay below certain altitude?  Other?



 do not archive



 Jesse Saint

 Saint Aviation, Inc.

 jesse(at)saintaviation.com

 C: 352-427-0285

 F: 815-377-3694

_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor
KCHD

carl.froehlich(at)verizon
Guest

Posted: Tue Sep 06, 2011 3:26 pm Post subject: Mogas in IO-540

I ran premium, no ethanol auto fuel in my 180hp IO-360 RV-8A and was pleased

with the results.  I operated the engine exactly the same as with 100LL.

The only difference I could tell was the spark plugs stayed cleaner (dual

electronic ignition with auto plugs).  Since the IO-540 has the same

compression ratio as the parallel valve IO-360, I would expect the same

results.  I do not recommend auto fuel on engines with high compression

pistons, or anytime if it has ethanol.



The problem you have is that no ethanol premium auto fuel is simply not

available for most people.  I asked the local airport to carry it but they

balked once they got their attorney involved.



Carl



--

jesse(at)saintaviation.co
Guest

Posted: Tue Sep 06, 2011 4:08 pm Post subject: Mogas in IO-540

That's great real-world experience.  How does octane work?  We have a tank of 89 Octane Mogas at our hangar for the Maverick and other small planes.  If I mix 5 gallons of 89 octane with 5 gallons of 100LL, does that average out to 94.5 octane?  Also, will the LL avgas stabilize the mogas if mixed, or would a fuel stabilizer still be needed if it was going to sit for a period of time?



Thanks for the input so far.



Jesse Saint

Saint Aviation, Inc.

jesse(at)saintaviation.com

C: 352-427-0285

F: 815-377-3694



On Sep 6, 2011, at 7:24 PM, Carl Froehlich wrote:



[quote] 

 

 I ran premium, no ethanol auto fuel in my 180hp IO-360 RV-8A and was pleased

 with the results.  I operated the engine exactly the same as with 100LL.

 The only difference I could tell was the spark plugs stayed cleaner (dual

 electronic ignition with auto plugs).  Since the IO-540 has the same

 compression ratio as the parallel valve IO-360, I would expect the same

 results.  I do not recommend auto fuel on engines with high compression

 pistons, or anytime if it has ethanol.

 

 The problem you have is that no ethanol premium auto fuel is simply not

 available for most people.  I asked the local airport to carry it but they

 balked once they got their attorney involved.

 

 Carl

 

 --

Kellym

Joined: 10 Jan 2006
Posts: 1705
Location: Sun Lakes AZ

Posted: Tue Sep 06, 2011 4:50 pm Post subject: Mogas in IO-540

Yes, avgas will stabilize the mogas to a degree. The octane boost would 

likely be a bit more than 50% because the first 20% or so of lead gives 

far more boost than additional amounts. I'd say you should be quite safe 

with 50/50 mix as long as you burned it within a few months.

On 9/6/2011 5:04 PM, Jesse Saint wrote:

[quote] 

 That's great real-world experience.  How does octane work?  We have a tank of 89 Octane Mogas at our hangar for the Maverick and other small planes.  If I mix 5 gallons of 89 octane with 5 gallons of 100LL, does that average out to 94.5 octane?  Also, will the LL avgas stabilize the mogas if mixed, or would a fuel stabilizer still be needed if it was going to sit for a period of time?

 Thanks for the input so far.

 Jesse Saint

 Saint Aviation, Inc.

 jesse(at)saintaviation.com

 C: 352-427-0285

 F: 815-377-3694

 On Sep 6, 2011, at 7:24 PM, Carl Froehlich wrote:

> 

>

> I ran premium, no ethanol auto fuel in my 180hp IO-360 RV-8A and was pleased

> with the results.  I operated the engine exactly the same as with 100LL.

> The only difference I could tell was the spark plugs stayed cleaner (dual

> electronic ignition with auto plugs).  Since the IO-540 has the same

> compression ratio as the parallel valve IO-360, I would expect the same

> results.  I do not recommend auto fuel on engines with high compression

> pistons, or anytime if it has ethanol.

>

> The problem you have is that no ethanol premium auto fuel is simply not

> available for most people.  I asked the local airport to carry it but they

> balked once they got their attorney involved.

>

> Carl

>

> --

_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor # 5286
KCHD

coop85(at)verizon.net
Guest

Posted: Tue Sep 06, 2011 4:58 pm Post subject: Mogas in IO-540

This has been a great thread.  I tried with no ill effects running Mogas in my Skybolt with an IO-540C4B5 but had limited experience with it so not a real valid example.  The one thing I'll offer as to the averaging of the octane rating is AVGAS and MOGAS octane ratings are measured differently so it's apples to oranges.  I have read several other places than 100LL equates to around 91ish MOGAS.  Now, the ethanol and aromatic properties of MOGAS that are not found in AVGAS are problematic but I don't know all the details beyond vapor lock is a big issue with the Ethanol.



Marcus

On Sep 6, 2011, at 8:04 PM, Jesse Saint wrote:






That's great real-world experience.  How does octane work?  We have a tank of 89 Octane Mogas at our hangar for the Maverick and other small planes.  If I mix 5 gallons of 89 octane with 5 gallons of 100LL, does that average out to 94.5 octane?  Also, will the LL avgas stabilize the mogas if mixed, or would a fuel stabilizer still be needed if it was going to sit for a period of time?



Thanks for the input so far.



Jesse Saint

Saint Aviation, Inc.

jesse(at)saintaviation.com

C: 352-427-0285

F: 815-377-3694



On Sep 6, 2011, at 7:24 PM, Carl Froehlich wrote:



[quote] 

 

 I ran premium, no ethanol auto fuel in my 180hp IO-360 RV-8A and was pleased

 with the results.  I operated the engine exactly the same as with 100LL.

 The only difference I could tell was the spark plugs stayed cleaner (dual

 electronic ignition with auto plugs).  Since the IO-540 has the same

 compression ratio as the parallel valve IO-360, I would expect the same

 results.  I do not recommend auto fuel on engines with high compression

 pistons, or anytime if it has ethanol.

 

 The problem you have is that no ethanol premium auto fuel is simply not

 available for most people.  I asked the local airport to carry it but they

 balked once they got their attorney involved.

 

 Carl

 

 --

Bob Turner

Joined: 03 Jan 2009
Posts: 885
Location: Castro Valley, CA

Posted: Tue Sep 06, 2011 5:47 pm Post subject: Re: Mogas in IO-540

"Octane" is a measure of gas' resistance to detonation. 

There are different tests in use, resulting in different numbers. The two most common tests are "motor octane" and "research octane".

Av gas is measured in "motor octane".

Car gas is the average of the two (note the R+M/2 posted on car gas pumps.)

87 octane car gas (regular) has a minimum motor octane of about 83 (and a research octane of about 91, so the average is 87). So regular car gas works okay in an engine certified for 80/87 (the first number is motor octane; the second is still a third way of measuring octane).

But even premium car gas, 91, is only about 87 motor octane, so it falls short of the spec for the IO-540.

As someone else said, the effect of tetraethyl lead is non-linear. The first small dose gives the largest increase, so mixing a 50: 50 mixture of premium car gas (87 motor octane) with 100LL will raise the octane more than half way (more than 93.5) so it should be okay in the IO-540.

_________________
Bob Turner
RV-10 QB

Kelly McMullen

Joined: 16 Apr 2008
Posts: 1188
Location: Sun Lakes AZ

Posted: Tue Sep 06, 2011 6:52 pm Post subject: Mogas in IO-540

If anything, the correlation between avgas octane and mogas octane

goes the other way. 80/87 is a bit higher octane than 87 mogas. I

expect it is the same on the higher grades. BTW for those that don't

know it, your model IO-540 in your Skybolt is the exact same engine as

Van's supplies, except for a lower rpm limit.

On Tue, Sep 6, 2011 at 5:55 PM, Marcus Cooper <coop85(at)verizon.net> wrote:

[quote] 

 This has been a great thread.  I tried with no ill effects running Mogas in my Skybolt with an IO-540C4B5 but had limited experience with it so not a real valid example.  The one thing I'll offer as to the averaging of the octane rating is AVGAS and MOGAS octane ratings are measured differently so it's apples to oranges.  I have read several other places than 100LL equates to around 91ish MOGAS.  Now, the ethanol and aromatic properties of MOGAS that are not found in AVGAS are problematic but I don't know all the details beyond vapor lock is a big issue with the Ethanol.

 Marcus

 On Sep 6, 2011, at 8:04 PM, Jesse Saint wrote:

 That's great real-world experience.  How does octane work?  We have a tank of 89 Octane Mogas at our hangar for the Maverick and other small planes.  If I mix 5 gallons of 89 octane with 5 gallons of 100LL, does that average out to 94.5 octane?  Also, will the LL avgas stabilize the mogas if mixed, or would a fuel stabilizer still be needed if it was going to sit for a period of time?

 Thanks for the input so far.

 Jesse Saint

 Saint Aviation, Inc.

 jesse(at)saintaviation.com

 C: 352-427-0285

 F: 815-377-3694

 On Sep 6, 2011, at 7:24 PM, Carl Froehlich wrote:

> 

>

> I ran premium, no ethanol auto fuel in my 180hp IO-360 RV-8A and was pleased

> with the results.  I operated the engine exactly the same as with 100LL.

> The only difference I could tell was the spark plugs stayed cleaner (dual

> electronic ignition with auto plugs).  Since the IO-540 has the same

> compression ratio as the parallel valve IO-360, I would expect the same

> results.  I do not recommend auto fuel on engines with high compression

> pistons, or anytime if it has ethanol.

>

> The problem you have is that no ethanol premium auto fuel is simply not

> available for most people.  I asked the local airport to carry it but they

> balked once they got their attorney involved.

>

> Carl

>

> --

_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor
KCHD

coop85(at)verizon.net
Guest

Posted: Tue Sep 06, 2011 7:32 pm Post subject: Mogas in IO-540

Interesting, so 100LL would have a higher octane than even 100 MOGAS if it existed?  I've seen the formulas but couldn't tell you what they were now, but the emphasis was the measurement was different.  Just everything I've read over the past 20 years suggests 100 AVGAS equates to a lower octane MOGAS.  Wouldn't be the first time I was wrong though.



Sent from my iPad



On Sep 6, 2011, at 10:50 PM, Kelly McMullen <apilot2(at)gmail.com> wrote:



[quote] 

 

 If anything, the correlation between avgas octane and mogas octane

 goes the other way. 80/87 is a bit higher octane than 87 mogas. I

 expect it is the same on the higher grades. BTW for those that don't

 know it, your model IO-540 in your Skybolt is the exact same engine as

 Van's supplies, except for a lower rpm limit.

 

 On Tue, Sep 6, 2011 at 5:55 PM, Marcus Cooper <coop85(at)verizon.net> wrote:

> 

> 

> This has been a great thread.  I tried with no ill effects running Mogas in my Skybolt with an IO-540C4B5 but had limited experience with it so not a real valid example.  The one thing I'll offer as to the averaging of the octane rating is AVGAS and MOGAS octane ratings are measured differently so it's apples to oranges.  I have read several other places than 100LL equates to around 91ish MOGAS.  Now, the ethanol and aromatic properties of MOGAS that are not found in AVGAS are problematic but I don't know all the details beyond vapor lock is a big issue with the Ethanol.

> 

> Marcus

> 

> 

> On Sep 6, 2011, at 8:04 PM, Jesse Saint wrote:

> 

> 

> 

> That's great real-world experience.  How does octane work?  We have a tank of 89 Octane Mogas at our hangar for the Maverick and other small planes.  If I mix 5 gallons of 89 octane with 5 gallons of 100LL, does that average out to 94.5 octane?  Also, will the LL avgas stabilize the mogas if mixed, or would a fuel stabilizer still be needed if it was going to sit for a period of time?

> 

> Thanks for the input so far.

> 

> Jesse Saint

> Saint Aviation, Inc.

> jesse(at)saintaviation.com

> C: 352-427-0285

> F: 815-377-3694

> 

> On Sep 6, 2011, at 7:24 PM, Carl Froehlich wrote:

> 

>> 

>> 

>> I ran premium, no ethanol auto fuel in my 180hp IO-360 RV-8A and was pleased

>> with the results.  I operated the engine exactly the same as with 100LL.

>> The only difference I could tell was the spark plugs stayed cleaner (dual

>> electronic ignition with auto plugs).  Since the IO-540 has the same

>> compression ratio as the parallel valve IO-360, I would expect the same

>> results.  I do not recommend auto fuel on engines with high compression

>> pistons, or anytime if it has ethanol.

>> 

>> The problem you have is that no ethanol premium auto fuel is simply not

>> available for most people.  I asked the local airport to carry it but they

>> balked once they got their attorney involved.

>> 

>> Carl

>> 

>> --

coop85(at)verizon.net
Guest

Posted: Tue Sep 06, 2011 7:34 pm Post subject: Mogas in IO-540

Great info, thanks!



Sent from my iPad



On Sep 6, 2011, at 9:47 PM, "Bob Turner" <bobturner(at)alum.rpi.edu> wrote:



 	  Quote: 	
		   

 

 "Octane" is a measure of gas' resistance to detonation. 

 There are different tests in use, resulting in different numbers. The two most common tests are "motor octane" and "research octane".

 Av gas is measured in "motor octane".

 Car gas is the average of the two (note the R+M/2 posted on car gas pumps.)

 87 octane car gas (regular) has a minimum motor octane of about 83 (and a research octane of about 91, so the average is 87). So regular car gas works okay in an engine certified for 80/87 (the first number is motor octane; the second is still a third way of measuring octane).

 But even premium car gas, 91, is only about 87 motor octane, so it falls short of the spec for the IO-540.

 As someone else said, the effect of tetraethyl lead is non-linear. The first small dose gives the largest increase, so mixing a 50: 50 mixture of premium car gas (87 motor octane) with 100LL will raise the octane more than half way (more than 93.5) so it should be okay in the IO-540.

 

 --------

 Bob Turner

 RV-10 QB

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=351609#351609

Kellym

Joined: 10 Jan 2006
Posts: 1705
Location: Sun Lakes AZ

Posted: Tue Sep 06, 2011 7:40 pm Post subject: Mogas in IO-540

As was posted earlier, avgas=motor octane

mogas=motor octane + research octane

87 mogas=~83 octane avgas

racing 104 octane mogas might get you to high 90s avgas.

Right now you can't get to 100 octane avgas unless either lead or some 

other higher octane chemicals like ethanol, MTBE etc are added and they 

have their own negatives.



On 9/6/2011 8:32 PM, Coop85 wrote:

[quote] 



 Interesting, so 100LL would have a higher octane than even 100 MOGAS if it existed?  I've seen the formulas but couldn't tell you what they were now, but the emphasis was the measurement was different.  Just everything I've read over the past 20 years suggests 100 AVGAS equates to a lower octane MOGAS.  Wouldn't be the first time I was wrong though.



 Sent from my iPad



 On Sep 6, 2011, at 10:50 PM, Kelly McMullen<apilot2(at)gmail.com>  wrote:



> 

>

> If anything, the correlation between avgas octane and mogas octane

> goes the other way. 80/87 is a bit higher octane than 87 mogas. I

> expect it is the same on the higher grades. BTW for those that don't

> know it, your model IO-540 in your Skybolt is the exact same engine as

> Van's supplies, except for a lower rpm limit.

>

> On Tue, Sep 6, 2011 at 5:55 PM, Marcus Cooper<coop85(at)verizon.net>  wrote:

>> 

>>

>> This has been a great thread.  I tried with no ill effects running Mogas in my Skybolt with an IO-540C4B5 but had limited experience with it so not a real valid example.  The one thing I'll offer as to the averaging of the octane rating is AVGAS and MOGAS octane ratings are measured differently so it's apples to oranges.  I have read several other places than 100LL equates to around 91ish MOGAS.  Now, the ethanol and aromatic properties of MOGAS that are not found in AVGAS are problematic but I don't know all the details beyond vapor lock is a big issue with the Ethanol.

>>

>> Marcus

>>

>>

>> On Sep 6, 2011, at 8:04 PM, Jesse Saint wrote:

>>

>> 

>>

>> That's great real-world experience.  How does octane work?  We have a tank of 89 Octane Mogas at our hangar for the Maverick and other small planes.  If I mix 5 gallons of 89 octane with 5 gallons of 100LL, does that average out to 94.5 octane?  Also, will the LL avgas stabilize the mogas if mixed, or would a fuel stabilizer still be needed if it was going to sit for a period of time?

>>

>> Thanks for the input so far.

>>

>> Jesse Saint

>> Saint Aviation, Inc.

>> jesse(at)saintaviation.com

>> C: 352-427-0285

>> F: 815-377-3694

>>

>> On Sep 6, 2011, at 7:24 PM, Carl Froehlich wrote:

>>

>>> 

>>>

>>> I ran premium, no ethanol auto fuel in my 180hp IO-360 RV-8A and was pleased

>>> with the results.  I operated the engine exactly the same as with 100LL.

>>> The only difference I could tell was the spark plugs stayed cleaner (dual

>>> electronic ignition with auto plugs).  Since the IO-540 has the same

>>> compression ratio as the parallel valve IO-360, I would expect the same

>>> results.  I do not recommend auto fuel on engines with high compression

>>> pistons, or anytime if it has ethanol.

>>>

>>> The problem you have is that no ethanol premium auto fuel is simply not

>>> available for most people.  I asked the local airport to carry it but they

>>> balked once they got their attorney involved.

>>>

>>> Carl

>>>

>>> --

_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor # 5286
KCHD

johngoodman

Joined: 18 Sep 2006
Posts: 530
Location: GA

Posted: Wed Sep 07, 2011 5:05 am Post subject: Re: Mogas in IO-540

It just so happens that 100 mogas does exist - our local RaceTrack guickie mart sells 100 octane Race Car Fuel. You won't like the price....

John



 	  Quote: 	
		  Interesting, so 100LL would have a higher octane than even 100 MOGAS if it existed?

_________________
#40572 Phase One complete in 2011

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