Av Gas & regular gas mix?

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gdavis
Posts: 52
Joined: October 12th, 2012, 8:55 am

Av Gas & regular gas mix?

Post by gdavis »

How advisable would it be to run a 50/50 mixture of regular unleaded pump fuel with avgas? I have heard that our engines actually produce a bit more power with regular unleaded, but I have been running avgas because of potential problems with the fuel cell because of the additives in modern fuels.
Any info would be appreciated.
Last edited by gdavis on September 30th, 2013, 9:20 am, edited 1 time in total.
FV80
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Re: Av Gas & reular gas mix?

Post by FV80 »

Greg,
Short term it should not harm anything, so give it a shot and see how it works if you want. Personally, I prefer to stick with Av Gas just for the relief from possible (probable) carb jet clogging from the (street type) fuel evaporating from the carb during garage time. It doesn't take much to create a problem, but will never happen with Av Gas. Av Gas (100LL) is specifically designed and engineered for small planes - long term storage and no harm to the carb from evaporation. It's also VERY consistent across the entire country, whereas the street gas you buy varies significantly from region to region - large metro areas to small towns, cold to hot temps, smog controls, none, etc.

Steve, FV80
The Racer's Wedge and now a Vortech, FV80
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brian
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Joined: June 26th, 2006, 12:31 pm

Re: Av Gas & reular gas mix?

Post by brian »

Just to add to what Steven said, only one race gas company obtains it's base stock from a consistent source, Shell. None of the other companies have their own refineries and supplies can vary from day to day. Granted, each company combines their own recipe of additives but the base stock will vary.
The above post is for reference only and your results may vary. This post is not intended to reflect the views or opinions of SCCA and should not be considered an analysis or opinion of the rules written in the GCR.
gdavis
Posts: 52
Joined: October 12th, 2012, 8:55 am

Re: Av Gas & reular gas mix?

Post by gdavis »

Steve and Brian,
I appreciate the advice. I am going to try mixing them until the last race of the season, when I will just run straight avgas to eliminate any possible winter storage issues.
problemchild
Posts: 902
Joined: June 25th, 2006, 9:34 am

Re: Av Gas & regular gas mix?

Post by problemchild »

If you believe unleaded pump gas will make more power, why mix it with Avgas?

The reason that I use Avgas is because I consider it a constant, theoretically anyway, meeting aviation standards with minimal contaminents. My engines are dynoed on avgas and I see very clean valves/valve seats that can go much longer without cleaning. Way too many reports of massive hp changes based on batches, venders, sales volumes, and QC at different stages of the fuel supply process, for me to believe that there is any positive reason, other than perhaps cost, to run pump fuel. Using my avgas vendor, I actually spend little more than for pump gas, and much less than for track fuel.

Once you mix avgas with pump gas, you have eliminated all the positives of the avgas.

If I had my own dyno, and time, I would purchase different pump fuel from different vendors in different seasons, test it all to find the most powerful, then hoard it, knowing that the next batch from the same vendor would likely be different. If I found something magical, I would have concerns that the oxygenation content would not pass the SCCA tests. Harding would probably discount my theory as worthless, but we have been successful with it.

When I buy fuel for the FITs and Zetecs, I attempt to buy from high volume name-brand stations, and avoid any fuel that admits to containing ethanol.
Last edited by problemchild on October 2nd, 2013, 8:19 am, edited 1 time in total.
Greg Rice
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brian
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Joined: June 26th, 2006, 12:31 pm

Re: Av Gas & regular gas mix?

Post by brian »

I agree with Greg. The only race gas company that uses it's own refineries is Shell. They say it makes a difference and I'm inclined to agree. Problem is that it is not approved for the Runoffs so why bother. I prefer av gas too, but can't run it at the Runoffs.
The above post is for reference only and your results may vary. This post is not intended to reflect the views or opinions of SCCA and should not be considered an analysis or opinion of the rules written in the GCR.
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