Let's do some math...
One US gallon of gasoline contains about 114,000 BTU. That is 45.42 horsepower.
But the rule of thumb for gasoline engine efficiency is that about 1/3 of the energy goes out as heat out the tailpipe, another 1/3 is lost in direct engine cooling (in our case that's cooling airflow, which has a drag penalty), leaving the last 1/3 to actually do work. So, you're actually getting about 15.1 HP/gallon of work, or "useful horsepower".
So, for 200 HP, you'll need around 13.2 GPH. Bottom line, sorry, you're just not going to get 200 HP out of 7 gph, let alone 5.
I understand the concern. You mostly cruise at 55-75% power. So you only use all available HP at T/O and climb. So I pretty much accept the high fuel flow because there is not much I can do during this phase of flight.Shooting for 10GPH or less at 200 HP is where I'd claim the math shows a problem.
Sure, now I will only land at airports with MOGAS on site. There are DOZENS of them!Sh*tcan the leaded fuel. Leaded fuel is the problem. Duh! Obviously.
Use unleaded fuel, high octane unleaded. Problem solved.
From an environmental standpoint, yes, for sure! But, unfortunately, Lycoming and Continental engines are made for leaded fuel, mostly because the lead acts as a lubricant for the top of the cylinder. Only a few of them (Lycoming O-320s, I think), have been STC'd for non-leaded fuels.Leaded fuel is still the problem. Whatever else is going on. How to get more airports to have unleaded fuel option may be a better question/problem to solve.
At 7.5:1 you don't see much need for 100octane.Lead is an octane booster. Octane is a measure of how much compression a fuel can take before detonating.
Octane is NOT a measure of how much energy the fuel contains.
Lead doesn't add or subtract energy (or, more accurately, ability to do work).
Removing (or adding) lead has nothing to do with the energy content of the fuel...
"Auto Fuel STCs are approved on 48 different engine types and 100+ airframes including nearly all 80/87 octane engines and the majority of airplanes in which these engines were installed. Several high compression engines are also approved for the use of 91AKI auto fuel including the 180 horsepower 0- 360 and the 115hp (or less) 0-235-L2C."Only a few of them (Lycoming O-320s, I think), have been STC'd for non-leaded fuels.
This.Leaded fuel is still the problem. Whatever else is going on. How to get more airports to have unleaded fuel option may be a better question/problem to solve.