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From the start, race fuels are typically cleaner and more consistent than pump fuels. The reasons why are due to economics and environment.
Pump gas…
How sweet the lead smells. Which also separates the street from the airport.
Appleseed said:How sweet the lead smells. Which also separates the street from the airport.
My first thought was also "Brain-poisoning lead?" 
Most race fuel is unleaded.....
Race fuel is real gasoline
Pump gas is a cluster of flammable hazardous waste products that need to be disposed of mixed with enough gas so it will light easy then tempered with 10% ethanol.
In reply to Appleseed :
Although most aviation gasoline is leaded (100LL), many race fuels are not... and there is no need for lead in any fuel in this century.
The difference between race fuel and street fuel? Are you in a race?
These guys? Yep, race fuel. 
Shame that race fuel isn't available in more places, at the pump. Understandable, absolutely, but still unfortunate.
That said, about 90% of the highway driving I do is just cruising anyway, so no real need for the good stuff, and the car makes plenty of power when I do need it, on a reasonable tune.
Still remember the smell of Q17 though... Mmmm... cotton candy and most likely carcinogens...
Race fuel vs pump gas?
You can crank up more boost before things go poof in an unfortunate way with it, and there is no ethanol in it to rot my rubber
That smell you notice with petrochemicals is from aromatic compounds. These can smell good, but they have a benzene ring in them, so they can also give you cancer.
How about the difference in BTU/gal?
Ethanol reduces this of course but even in pure gasoline this can vary. Does race gasoline go to outer limits of gasoline , like above the 114,000 btu/gal the internet says pure gasoline has to offer? Internet says E10 is 111,836 btu/gal.
https://en.wikipedia.org/wiki/Gasoline_gallon_equivalent
In reply to te72 :
Sunoco across the street from Racer Walsh sells 100LL at a pump and it is expensive!
What Separates a Race Fuel from a Street Fuel?
The price!
In reply to te72 :
Love the Q16.. Cotton candy & Red Bull!
In reply to alfabeach :
In the current Google Street View images, that Sunoco (at Beach and Foster in Jacksonville) sells 100 octane unleaded, not 100LL ("low lead" aviation gasoline). 100LL would be completely inapproriate; 100 octane unleaded sounds good for some cars.
Dad had some 100LL that he would run in his XKE when they started only selling unleaded. He would buy premium unleaded and add a gallon of the av gas in the summertime. When you could get leaded regular, he would mix those. Apparently the lead in the 87 octane would bump up the effective octane in concert with the premium unleaded, or that is what the petrochemical engineer that lived next door said.
A real eye opener was when I had a car on the dyno and it made 565whp on the dyno ( @25psi), which was way out of my pump gas experience power-wise, and the person who was holding my hand through this new experience said "Oh yeah, with C16 you'll be able to pour the pistons out the oil pan before you run into detonation."
Later, I street tuned a different, bigger turboed car on C16 that made 730whp (@23psi).
On E85, that same engine/turbo combination made 810whp. 10% more power on E85 than "race gas".
$18/gallon and eats plugs and WBO2s for C16, or $2.50/gallon for E85 and sensor/plug friendly... Decisions decisions... hmm.... let me think...
Note: C16 exhaust smells 300% better than the noxious crap that is E85 exhaust. If it weren't for the plug fouling issues, I'd run C16 in my lawnmower just for the fresh cut grass plus race gas smell.
For pump gas we used to go across the corner to the Sunoco where they had 94 octane. I run my Mazdas on 87 and I run my VWs and Volvos on BP 93. The Sunoco 94 smelled... different. The exhaust was "sweet", kind of halfway between proper leaded race fuel and generic stuff. It's a shame they don't sell it anymore.
Anybody who says leaded fuel has no place in the 21st century doesn't recognize the EXTREME efforts made before and during WWII, when any and all avenues for knock resistance were explored, because more knock resistance meant higher boost pressure available for fighter aircraft, which were almost universally supercharged/turbocharged to the point where knock was the ultimate power limiter, even at altitude. Allied engineers experimented more with fuel compounds, German engineers experimented more with water injection and nitrous oxide. (Some of the best prewar water injection data comes from Ricardo, however)
Most of what we know today about detonation-resistant fuel compounds dates to frantic research in the early 1940s. We use tetraethyl lead as a fuel additive because extensive testing showed that it freakin' WORKED. (As did, I believe, triptane, which I undertstand has a knock index in the 260 range) My GUT feeling is that it is the toluene that makes the "race gas" smell. But what does it know? Your gut is full of sh...
In reply to Brian_13 :
I add "leaded" Torco to my unleaded premium fuel to get the octane I need. Race fuel is outrageously expensive and E85 is hard to find and I don't want to tote around 55 gallons of it.
Knurled, it's obvious you know your stuff. Hot Rod ran an excellent article a while back on the history of ethanol as a fuel in America. Long story short, it was mostly a matter of money greasing the right wheels in politics, which enabled tetraethyl lead to become the primary anti-knock additive here in the US. If you really wanna read the article let me know and I'll see if I can find a link.
Toebra, lead as an additive in fuel makes for fantastic knock resistance. However, it has the whole toxin thing going for it too... Totally makes sense that your dad would run a mix like that.
My Supra puts out just shy of 500whp on 91 octane with anywhere from 10-15% ethanol in it, since you can't get ethanol free in most places, and E85 would be a terrible choice for traveling, even if you could get it. Next step for me is likely installing the water methanol setup, and seeing if we can crack the 600whp barrier with the same turbo I have on now. 
The octane Boosters separates a Race Fuel from a Street Fuel.Lead is used in racing fuels because it is a very effective octane booster.
Knurled. said:
Anybody who says leaded fuel has no place in the 21st century doesn't recognize the EXTREME efforts made before and during WWII, when any and all avenues for knock resistance were explored, because more knock resistance meant higher boost pressure available for fighter aircraft, which were almost universally supercharged/turbocharged to the point where knock was the ultimate power limiter, even at altitude. Allied engineers experimented more with fuel compounds, German engineers experimented more with water injection and nitrous oxide. (Some of the best prewar water injection data comes from Ricardo, however)
Most of what we know today about detonation-resistant fuel compounds dates to frantic research in the early 1940s. We use tetraethyl lead as a fuel additive because extensive testing showed that it freakin' WORKED. (As did, I believe, triptane, which I undertstand has a knock index in the 260 range) My GUT feeling is that it is the toluene that makes the "race gas" smell. But what does it know? Your gut is full of sh...
I don't think I would go that far- back in WWII, it was all about performance and winning a war, effects on human life over the long term was not even considered. Now that we know the long term effect on lead poisoning, especially when put airborne, it does illustrate that for the 21st century, TEL is a bad idea for the market. There's been enough development in physics and chemistry to understand what knock really is and find better solutions than TEL for octane boost.
In reply to Knurled. :
That's all good stuff about the 20th century. Technology has advanced since then, and we've also realized how stupid some practices (such spewing lead in exhaust) are. Today, even Formula 1 runs on unleaded gasoline.
alfadriver's comments on this hit the nail on the head.
In reply to Scargod :
Need and cost are relative things. If you can't afford to operate it, I suggest not building it.
Brian_13 said:In reply to Knurled. :
That's all good stuff about the 20th century. Technology has advanced since then, and we've also realized how stupid some practices (such spewing lead in exhaust) are. Today, even Formula 1 runs on unleaded gasoline.
alfadriver's comments on this hit the nail on the head.
Technology has advanced to where we don't need as much detonation resistance in the fuel to get suitable performance. For one, we don't need 120+ octane gasoline for automobiles day-to-day. (Some of the aviation fuels were rated to 140-150 but a lot of those numbers were a lot like treadwear ratings...)
For two, we run our military equipment on something around kerosene-like thanks to jet engines and turbines and Diesels. The military even has Diesel powered dirtbikes, because fuel commonality. We don't NEED to try to eke out more power from overstressed piston engines prop planes. Which is a lot of why fuels science sort of died out after the 1940s, when jet engines started to come into play.
te72 wrote:Shame that race fuel isn't available in more places, at the pump. Understandable, absolutely, but still unfortunate.
But why? It burns more slowly, yes, but if you can't take advantage of thar because you don't have high enough compression to need it, nor a 'hunt forward' igniion timing set up, it won't do you any good.
We get good unleaded 94 octane with no ethanol here at the pump, and I can't imagine needing aything else.
I drained 8 gallons of Avgas out of a plane and put it in Mr. Truck, woke his butt right up! I later found out 110LL doesn't gum like auto gas, cleaner? No Ethanol?
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