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RobertSmalls · 05-11-2010, 05:19 PM

Lean burn: 69.7mpg on a 6.4mi loop @ steady 50mph
P&G: 71.6mpg on the same loop @ 45-55mph

During the first run, I just "drove normally". That means cruising in 5th gear at 45mph in one section and 50mph in another, and slowing down if that's what it takes to hold lean burn. During the second run, I did P&G. When vehicle speed dropped to 5mph below cruising speed, I'd tap the throttle to re-start the engine, give it 60% throttle in 3rd gear (2200-2700RPM), then shift to N and hit the engine kill switch when I got to 5mph above cruising speed.

It was a 6.4mi loop of country roads, with five complete stops and four right turns. The course was somewhat flat, there was little wind, and no traffic on my tail. Conditions: 53°F ambient, engine fully warmed up, electric assist switched off.

P&G didn't beat lean burn today. I think there are conditions under which it would, though.

The course I laid out happened to be about as good as it gets for lean burn. If I had been cruising at 120mpg instead of 80-90, then lean burn would have wasted more revs compared to P&G. Maybe my 3rd gear P&G was sub-optimal? Would I have gotten better results in 4th?

I will P&G at the next hilly fuel economy run for sure, but until then, I'm going to keep on cruising in lean burn, knowing that my efficiency is near P&G levels, without the fluctuation in speed.

05-11-2010, 05:19 PM	#1 (permalink)
RobertSmalls Left Lane Ecodriver Join Date: Aug 2008 Location: Buffalo, NY, USA Posts: 2,257 Prius C - '12 Toyota Prius C Thanks: 79 Thanked 286 Times in 199 Posts	Experiment: Insight Lean Burn versus P&G Lean burn: 69.7mpg on a 6.4mi loop @ steady 50mph P&G: 71.6mpg on the same loop @ 45-55mph During the first run, I just "drove normally". That means cruising in 5th gear at 45mph in one section and 50mph in another, and slowing down if that's what it takes to hold lean burn. During the second run, I did P&G. When vehicle speed dropped to 5mph below cruising speed, I'd tap the throttle to re-start the engine, give it 60% throttle in 3rd gear (2200-2700RPM), then shift to N and hit the engine kill switch when I got to 5mph above cruising speed. It was a 6.4mi loop of country roads, with five complete stops and four right turns. The course was somewhat flat, there was little wind, and no traffic on my tail. Conditions: 53°F ambient, engine fully warmed up, electric assist switched off. P&G didn't beat lean burn today. I think there are conditions under which it would, though. The course I laid out happened to be about as good as it gets for lean burn. If I had been cruising at 120mpg instead of 80-90, then lean burn would have wasted more revs compared to P&G. Maybe my 3rd gear P&G was sub-optimal? Would I have gotten better results in 4th? I will P&G at the next hilly fuel economy run for sure, but until then, I'm going to keep on cruising in lean burn, knowing that my efficiency is near P&G levels, without the fluctuation in speed.