Re: C12 vs pump gas
 

The readings from one gas station to the next will usually vary , and that's true across the nation . Certain Brand name stations will put only their own gasoline in the tanks , so they're more consistant . Others purchase which ever brand fuel is the least expensive on a given day .
And computerized , fuel injected engines can adjust themselves for changes in gas quality , up to a point . So very precise quality control isn't really needed .
If pump gas quality is a necessity , always go with a Top Tier gasoline . Shell belongs to that program , so does Chevron .

Re: C12 vs pump gas
 

C-11 seems to work well in the low comp. MoPars. Jim

Re: C12 vs pump gas
 

There are several schools of thought on this

What I was told years ago was that the Racing Fuels were a lower density than Pump Gas.
AND It Burns Slower than lower Octanes.

Back in 90's, the racers that ran low compression rides like 455 Firebirds, 6 Cylinder Maverick, Pintos told me to get the racing gas to work they did two things.

Leaned out the Carb and bumped total Timing to 50 degrees.
This seem counter intuitive to me but watched them set records.

Not sure, think they had to use a cooler Plug too.

Not what you want to do for the street or road racing but worked for short duration sprints for drag racing.

Re: C12 vs pump gas
 

Octane slows down the burn rate of fuel. As you add compression you are adding heat by increasing cylinder pressure so you add octance to keep the fuel from spontaneously combusting (detonating). If you don't have enough heat and too slow of burning fuel, it will not light consistently and you can get the miss you are describing. C-12 is 108 motor octane which is probably too much. Try a 110, although ours (Renegade) is 108 octane also, but we have a Blue haze 110 that is only 105 motor octane. You can mix 110 with premium pump gas and you may find a nice happy medium. You'll get enough octane for protection but not too much to light. My son ran this combo in a 350 cu, 10:1 engine and won back to back track championships at Indianapolis Raceway Park.
PS, not saying mixing fuel will win rounds, he is just a helluva driver...but it did keep the engine together.

Good luck!

Ron Finney - 396V S/C
Indiana Distributor for Renegade Racing Fuels

Re: C12 vs pump gas
 

Not sure about other parts of the country but here in Houston that is the way I would say 90% of the fuel is mixed. All gas is "regular" unless you add the percentage of X to make it "Super". They all self mix in the trucks. My dad would tell me that you would see every brand of truck from Shell to Valero to Texaco lined up at the gas racks. Unless it is a corporate station all the gas comes from the same place. You can usually tell the corporate stations because it will be .30 higher. Just because you go to a chevron and think you are getting your "Techron" it is the same gas, from the same truck, that just left the shell station down the street. That is just the way it is.

Re: C12 vs pump gas
 

My car ran well on Torco 112. It doesn't like VP-C12. C-11 is too expensive, but its low motor octane makes it work well for stockers. I now use Sunoco 110. I'm happy with the way it performs.