Is Avgas a Good Alternative to Ethanol-Free Gas?

Colin
By Colin Wood
Jan 13, 2021 | fuel, gasoline, Avgas

On paper, running aviation-grade fuel might sound like a great idea since it has a relatively high octane along with no ethanol.

In practice, however, it may not be the best idea, even if you do manage to get your car out onto the taxiway.

Learn more about avgas—and why you might not want to run it in your car—over on Classic Motorsports.

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Comments
alfadriver (Forum Supporter)
alfadriver (Forum Supporter) MegaDork
1/12/21 11:17 a.m.

If you want to poison your exhaust system with lead, it's not bad.

But if you don't want lead to coat your WB sensors, let alone the catalysts, it's a terrible idea.  

914Driver
914Driver MegaDork
1/12/21 12:07 p.m.

I drained 10 gallons out of a plane I bought, put in in my carbed C-1500 mixed with pump gas.  Oh MY!  Mr. Truck liked it, don't get used to it Hon.

I give them a drink of Ethanol free 91 once in a while, but a carbureted race car, abaloobie. 

dean1484
dean1484 GRM+ Memberand MegaDork
1/12/21 12:48 p.m.

Ok another question re Avgas.  Internet myth and legend is that it will cause pistons to burn or valves to burn.  I never had that problem.  I never have got a "real" answer on this.

alfadriver (Forum Supporter)
alfadriver (Forum Supporter) MegaDork
1/12/21 1:37 p.m.

In reply to dean1484 :

That myth makes no sense to me at all.  This fuel is specifically designed to be the most reliable fuel ever.  

Paul_VR6 (Forum Supporter)
Paul_VR6 (Forum Supporter) SuperDork
1/12/21 1:38 p.m.
alfadriver (Forum Supporter) said:

In reply to dean1484 :

That myth makes no sense to me at all.  This fuel is specifically designed to be the most reliable fuel ever.  

Lazy O2 sensors is really the only downside, IMO

APEowner
APEowner GRM+ Memberand Dork
1/12/21 1:39 p.m.

I run 100LL in my Formula Ford.  It's easier for me to get than race race and it makes the exhaust smell great!  It does mean that I can't leave the O2 sensor for the data acquisition system in the exhaust all the time.

03Panther
03Panther SuperDork
1/12/21 1:43 p.m.

In reply to dean1484 :

That myth started because the general public thought that the higher the octane number, the “hotter” the fuel is, and gives a “motor” more power. 

Not how octane number work at all

03Panther
03Panther SuperDork
1/12/21 1:49 p.m.

I’ve never personally bought any Av gas; I assume there are also different grades of av gas available?

i also do not know what 100LL is. Have heard it mentioned before, but would not know where to get it. 

There used to be some places that had Cam2 at the pump, but it’s been many a year since I’ve seen that 

Paul_VR6 (Forum Supporter)
Paul_VR6 (Forum Supporter) SuperDork
1/12/21 1:56 p.m.

https://www.shell.com/business-customers/aviation/aviation-fuel/avgas.html

If you have a track or VP dealer closer than an airport, it's usually easier to just buy race fuel.

Curtis73 (Forum Supporter)
Curtis73 (Forum Supporter) GRM+ Memberand MegaDork
1/12/21 1:58 p.m.

100LL is 100 octane, low-lead.  As the article points out, the octane number is not derived as R+M/2 like automotive gasoline, 100LL is actually a bit higher in octane than 100 by automotive standards.  100LL is typically called Avgas, sold at airports for ICE aircraft.

Avgas is closer to white gas than gasoline (think coleman fuel).  It has a higher vapor pressure so it doesn't boil at higher altitudes, and on the average lower BTU content than gasoline - approximately 112kbtu/gal for Avgas vs an average of about 120kbtu/gal for gasoline.  (typical range of 115k-125k.  E15 is about 114k)

So, yes, Avgas has higher octane, but it isn't what I would call a performance fuel

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