WOW, Bambikiller and I agreed on 2 things this week!
Any way, I was at the airport yesterday, and Avgas 100 was about $2.50 /gal. That is NOT cheaper than car gas. Also, like said before, it'd better refined, has additives & such. BTW, the COLOR is also so you can tell what octane it is:
80/87 octane = red
100LL (100 octane, low lead) =blue
100/130 = green
115/145 = purple
Jetfuel - A = amber
(ASTM D910-75)
From racing model powerboats with 2 cycle ( 15k RPM) engines with 10 :1 to 16:1 (on modified) compression, we have figured out that the lower octane gas gets you more horsepower in the lower compression, stock engines. That means your basic Ford Escort makes best HP with the 87-89 octane gas, like the owner's manual says. Just make sure you go someplace with good "quality " gas. I filter mine through a coffee filter when filling the boat can and I found dirt once!
FYI: they use ethanol, as one way to increase octane. Neat idea? Don't recommend you try it yourself...