Experiment: Insight Lean Burn versus P&G

[RobertSmalls]

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.

[dcb]

I'd be lying if I said I didn't have insight envy

[Daox]

Wow, I missed this thread. Thanks for posting the link it in some other thread!

[azaviator]

I think it all depends on how slow you let it get on the 'glide'. I use my FAS switch on the city streets to coast down to a light, usually a third of a mile or more depending on the timing of the light and traffic, and I have noticed a pretty strong gain on this tank. Usually I top at 45mph and let it coast down to about 20mph before the light allows me to accelerate again. This 'seems' (butt dyno) to have improved my mileage over using just lean burn in the city.

It is my first tank with heavy use of the FAS switch, so I haven't tried to track it over the short term, since I'm more interested in the overall tank miles (still trying to break the elusive 900 miles on a tank). It would be nice to know what the changeover point is for better mileage using lean burn or P&G (or both together).

Keep up the good work!!