Subscriber question:
"I’ve read about leaning on taxi to save fuel, but I don't think it's worth the risk of a lean-mixture takeoff to save a little gas. My instructor agrees with me. What do you think?" —Aiden R.
Tom:
“If saving fuel hasn’t convinced you to lean the engine while taxiing, have you considered the environmental impact of emitting more lead into the atmosphere? Recent reports suggest leaning while taxiing can reduce lead emissions on the ground by at least 20 percent. Considering that GA flying is under high scrutiny by environmental groups and some municipalities, we should do all we can to fly in a friendly way.
Because of lead emissions, two airports in Southern California have eliminated the availability of 100 low lead, and others are now looking into doing the same thing. So, consider pulling the red knob way back right after startup. A Continental IO-550, for example, at about 1000 RPM burns about six gallons per hour. Pulling the mixture back to about three gallons per hour cuts your emissions substantially. And, of course, on a 10-minute taxi out, you’ll also save nearly half a gallon of fuel. With the national average of 100 low-lead at $6.19—and many places more than that—you can pocket about three bucks, and save on future maintenance through reduced spark plug fouling and by having a cleaner engine.
Remember though to pull the mixture back to the point that the engine will stumble if you try to apply full power for takeoff without enriching the mixture again. Tell your instructor that the taxing, while that lean, will not hurt the engine and that you want to save money, as well as reduce your environmental impact.
Lean and be green while we all look forward to the availability of a high-octane, unleaded fuel for the entire GA fleet.”
Imagine you're at the pumps and you can buy either 100LL or a lead-free 100-octane avgas—but the lead-free costs more. Would you pay extra for lead-free aviation fuel?