P&G - how wide of speed is needed?
 

Much of my driving conditions are moderately loaded highway - not necessarily rush hour, but no way in hell can I slow down to 40mph. How "narrow" can you effectively P&G in and how much does it affect your overall efficiency? Would even like 65mph->75mph work?

Depends on your car aero, but I think 65-75mph is too fast - glide is not long enough, it is probably better to just use steady 70mph speed.
55-65 or 50-65 would be better.
YMMV

I've gotten great results in my car, extending the "glide" phase with very light gas pedal pressure... IE, getting up to 65, then slowly decelerating to 50ish. The glides last almost forever and I can easily break 100 MPG the whole glide portion. I don't know how flat your roads are, but I have gotten my best results (and least stressful for me!) by just watching the lay of the land, and using it to my advantage--that is to say, "gliding" with light power up hills, then regaining lost energy on the downhill portion.
Even moderate slopes on highways give great results. My highway trips are usually 50MPG+

I go 55-65 generally, and sometimes 50-65. Forty is too slow on a freeway and you might cause an accident if it's crowded or get a ticket when it's not. I have also had good results doing P&G with the engine on. Here is a test I did: http://ecomodder.com/forum/showthrea...tml#post252933

If you have any elevation changes use them to accentuate your P&G. The road I get on when I leave my neighborhood runs parallel with the railroad tracks which are basically level. I'ts an excellent teaching tool for gliding when you can see the road drop compared to the RR tracks. Coasting distances can easily double when you do it downhill, even when the downhill portion is very a slight grade.
Perfection would be where you can coast downhill and pulse uphill at best BSFC, without any change is speed whatsoever. That would allow you to avoid the exponential increase in aero drag in the pulse portion on flat ground. This has proven to be the best scenario for highest mileage in contests.

regards
Mech

I like a 10mph drop in speed before accelerating on the highway, 15 is great if you can get away from it. However, in town I find that 5 mph can be quite a long glide.

I can happily use a 5 mph span in tight traffic. 10-15 mph is what I generally do on the highway when conditions allow. On backroads with no traffic and no rush? PSL+10 down to below 20 mph.

I saw several MPG gain going from 45-55 down to 40-55. 55 to 50 drops fairly quick. 50 to 45 takes probably 50-100% longer. 45 to 40 takes probably another 50-100% from 50 to 45! If it's even a tiny downhill slope, I could be going ~43MPH the whole way down! I'm sure every car/road is going to give different result, but I definitely found 15MPH between P+G to be the way to go.

Back when I P&G'd out in the sticks I went 60-25 with the Coupe. 25 was about as slow as I cared to go in 5th. Made for a gentle bump start too.

on the highway I love 60mph to 40mph

I used to do a lot of P&G between 50 and 60 when I had a long commute to school. Also, any time there was any downhill, I'll pop into neutral for a cost. That's where I got most of my gains. Steady speed on the uphills (higher load for motor while it's pushing and storing kinetic energy) and then neutral for the downhills.

For those of us with auto (dog-a-matic) transmissions, you might check to see where it will shift out of top gear and end your glide before that speed. With my RAM, it will shift into 5th at 45mph, but I can sometimes get it to coast down to 40mph before downshifting...

P&G, something I've really not tried yet. I'm taking notes here.

My car is a 94 saab, can't use scan gauge. I pg all the time, but I don't know if it works or not. Accelerate. hard up to 75. Coast to what ever speed when the car behind me starts catching up. I,m thinking on lowering my idle so my coasts sip less fuel. Sc

That's the same for me. 55-25 when traffic allows. Obviously can't get away with less than 50 mph safely on the hwy most of the time though.

I think that it is funny how people suddenly develop road rage during a normal conversation inside somewhere when I mention driving fifty-five miles an hour.

Calm down! :)

The suggestion for acceleration is 3/4 throttle based on a 1970s BMW study of fuel economy.