bobandbrigit, BLE and Floyd all make good points. Note BLE’s “you can actually get worse gas mileage using this technique”, and “pulse and glide really pays off … around 40mph or less”. I guess those economy runs that were mentioned on the program and on this thread fall into that category, so aren’t relevant to Linda’s husband’s practice, which seems to be, or include, at highway speeds. I would also discount all coasting in neutral or even switching off the motor, as that is obviously falsifying the “game”, and also not what Mr Linda does, which is alternately flooring and fully releasing the gas pedal.
I have to say I’m surprised at those who say hilly country gives better mileage than flat, although obviously I have to believe what they say. But I suggest that most people don’t have a choice of whether to make a given journey on either hilly or flat roads, so the relevant question is how you get the best mileage on the flat, not what mileage you could get if you were on some different journey. And in any case, again, Linda didn’t mention hills as part of the scenario.
Some anecdotes:
Long ago, I drove in a convoy of British Army Land-Rovers from Brighton to Colchester, which is about 120 miles. Practically all was on what in the USA would be a state or interstate highway, so there were few stops for traffic-lights and such, and the majority was on pretty level ground. The convoy kept close together, so obviously the road traveled and max and average speeds were identical for all participants, and the vehicles were pretty much identical and similarly loaded too. Now, the interesting thing is that my truck, uniquely I think, had a hand-throttle - a ratcheted lever that enabled me to fix a desired throttle opening and take my foot off the pedal. Any time I met a slight grade, or needed to close up or open up in the column, I just moved the lever a couple of notches, so as to produce the minimum necessary change in throttle-opening. On arrival, we all gassed up: my truck took 8 Imperial gallons, and ALL the others 9 or more.
Years later, I owned an old Chevy Caprice, with V8 engine and of course 3-speed auto gears. My very senior mechanic knew those cars - he had managed the Belgian government’s small fleet of them, decades before. He advised me to get up to my desired speed as fast as possible, and then stay there. That ties in with BLE’s “engines become very inefficient at light loads” - get out of partial load, and incidentally low gears, as soon as you can - but definitely not with Mr Linda’s alternate flooring-and-releasing thereafter. Incidentally, we never heard whether Mr Linda’s car has auto or stick shift. If auto, wouldn’t every flooring of the pedal cause a downshift? Repeated constantly over a journey, that would be a huge waste of energy right there.
Related to satisficer’s BMW story: in previous decades, many French cars were set up so that a tiny gas pedal movement got you direct to full throttle-opening; most of the pedal movement being just window-dressing. So unless you had a really fine feel for the pedal, you were pretty much obliged to use Mr Linda’s on-off technique, whether you wanted to or not. We always thought this was a manufacturer’s trick to make you think your car (which would always be seriously underpowered by US or even British standards) was more sporty than it really was. But in light of this thread, I guess it could have been an economy move too. Those cars were stick-shift, of course.
Reverting to auto shift: I’ve just bought a ’94 Le Baron convertible, with 3-litre engine and conventional 3-speed auto box plus, I understand, a lock-up overdrive 4th gear added on. And I was astonished, and even a little scared, at the big burst of gas away from rest that a little pedal movement gave me. This seems set up to encourage just the “get up to speed quickly and stay there” technique that my mechanic recommended. I don’t know how that works out yet, but it may be relevant that this car was considered a gas-guzzler, for its size and power, even in its own day: a contemporary consumer report says 20mpg (US) city, 28 highway.