Av gas

[Jeff Stout]

Originally Posted by Adger Smith

Does any one want to tell what the dual rating on AV gas is about? like 115/145 ??
Choices:
A. Heat value
B. Resistance to engine icing
C. Octane
D. Volatility rating

The Lean Mixture rating is 100 octane (15 octane higher than the comparable 85 MON for unleaded Mogas) but Avgas also has a Rich Mixture rating of 130 which allows higher supercharger boost pressures to be used without detonation occurring.

I thought the high number was heat value, but I cheated and went to google

[Shake & Bake]

When I use to do a lot of street racing back in the day I would buy AV gas from the local airport.(Told them I was using it at the dragstrip). They told me it was 105 octane. I would then mix Super 104 +" Real Lead" with it to up the power a little more.
Adding one quart of "Real Lead" additive in 20 gallons of AV gas would take it up another 5-7 numbers.
Seriously, 1 gram of metallic lead per gallon of gas equals a level of protection no substitute can match....Not to mention it stops knocks, pings, run-on, overheating and piston damage caused by fuel that's too low in octane.

[Bob Mulry]

115/145 was 115 octane lean & 145 Auto Rich or Military Power...

We also had a a J-34 jet engine under each wing that used 115/145 for fuel and part of our pre-flight was to reach inside the tailpipe to break of the stalactites of lead from the fuel.

Flew in P-2V Neptunes .......2 turning & 2 burning

[Jeff Kempton]

Originally Posted by Bob Mulry

115/145 was 115 octane lean & 145 Auto Rich or Military Power...

We also had a a J-34 jet engine under each wing that used 115/145 for fuel and part of our pre-flight was to reach inside the tailpipe to break of the stalactites of lead from the fuel.

Flew in P-2V Neptunes .......2 turning & 2 burning

As soon as I started reading the second paragraph I thought "This guy flew in Neptunes!" lol

I didn't, but I'm familiar with them. We have one on display at an aviation museum that I'm involved with, and the Royal Canadian Air Force also flew them for a few years.

[Adger Smith]

We have some winners...Basic.. rich lean octane..
The only thing that hasn't been mentioned is the chemical enhancement that AV gas has to help keep Carb ice from forming. It doesn't cool like racing gas when it evaporates/vaporizes. So it puts some heat in the induction system that race gas doesn't.
Personal Experience:
My 172 with the 300 Continental "6" engine runs better on a 50/50 mix of 100LL Av Gas and non ethanol 87 octane pump gas. Simply because the engine was designed for 85 octane gas. I have an STC to fly with automotive gas, but the mix is better.

BTY: Jeff and Bob I have an old friend that has been working for a company leasing planes to the Govt. for fire suppression. He started off flying a modified Neptune and moved up to a DC-10. Somewhere I have a video of him in the Neptune making a run on a ridge that was on fire... Cool stuff.