Pulse & glide not always better than steady speed in-gear?

[i90east]

I've read a number of posts on here over the years in my efforts to learn the best possible way to drive my stick-shift 2010 Hyundai Accent. I figured out a good routine for suburban driving without having any experience on the highway. Lately circumstances have changed and now I'm on the highway a lot. So I had to relearn how to get optimal MPG.

I did pulse & glides throughout a tank, pulses to 70 MPH (a little more when on a hill to reach the top) coasting down to 55 repeatedly on the highway and pulses to whatever I could get up to in town in order to coast down to 0-20 before applying brakes for lights or traffic. This tank got 36 MPG overall.

On the next tank I removed the pulses and most of the glides except for significant downhills and when slowing for lights and traffic. Instead I stayed in 5th gear, keeping my throttle % at a point that maintained 55-65 MPH on the highway and the speed limit in town. This tank got 43 MPG overall, a very significant improvement.

On the first tank I was getting 20 MPG during highway pulses and 250 MPG on highway coasts but the pulses would take a while due to my car's weak engine. It had me wondering if pulse & glide is better suited for cars with more powerful engines that could go from 55 to 70 MPH more quickly. With the throttle position held steady on the highway holding 55-65 MPH the MPG reads 39-42.

I've gotten the impression from what I've read on here that pulse & glide is always better than staying in gear at a steady speed but I don't seem to be reaping the benefits of that somehow. I know engine-off coasting is a bit more effective than leaving the engine on but I'm concerned about the extra wear and tear. Perhaps staying in gear is better in some cases.

[Baltothewolf]

Your pulse window and speed is way to high. 55-62 seems to be the sweet spot for P&G. Any higher and you start meeting higher wind resistance = speed drops faster = less gain from P&G. I drive 70-75mph on the freeway now, and I never P&G. I found using it over 65mph reaped same results as you. Lower MPG.

[j12piprius]

My civic has a high rpm, and peak power at 5500 rpm. Maybe for that reason, the mileage is much better with pulse and glide, than it is with driving at a steady light throttle.

I've tried the latter several times, averaged about 10 mpg worse, and immediately went back to pulsing and gliding.

For my car, I think the difference between going an even speed and pulsing is not that much, compared to the great benefits from gliding. Also, pulse & glide is more effective the longer the glide, thus with better aerodynamics of the car.

[cowmeat]

Back when I was driving Black Widow, which is not an aerodynamic vehicle to say the least, I saw an immediate 8 mpg jump when I began EOCing to lights.
That encouraged me to begin P&Ging, and I ended up gaining another 8 mpg. I started out at around 42-44 mpg, and was able to pull over 60 mpg on one tank.

I stayed off highways and would P&G from 55 down to 35 and back, and it worked awesome for that car.

Now that I have Turtle I only EOC to lights. I have never tried to P&G in the Insight, even though it's a perfect platform for it since it autostarts. Problem is that it draws a lot of juice when the motor is off, since I leave for work when it's dark and return home when it's dark so I have the lights on pretty much every time I drive it. So I have to charge the 12V every night just to EOC, or it runs down the tiny 12V battery, which also runs down the IMA battery.

[dirtydave]

How many RPM's in 5th at 55MPH??

[Fat Charlie]

Terrain dictates. Every platform, road and driver have differences. The conditions you're in and your goals at the moment (how much of a rush are you in?) are even more changeable, so the effectiveness of different techniques changes with them. YMMV, as it were.

What kind of instrumentation do you have? Instant and trip are the bare minimum, but short trip is where you can compare different conditions and techniques. Comparing your morning commute numbers to other morning commute numbers will teach you a lot more about conditions and techniques than just tank to tank and instant mpg numbers.

[dirtydave]

Pulse downhill and coast uphill

[jakobnev]

Pulse up, glide down dammit!

[dirtydave]

I don't know about you but my car gets bad MPG uphill...
Much better downhill....

I only run the engine down hill, more MPG no?

[awcook]

Depends on how the vehicle acts on hills. My car is terrible for gliding up hill but great for going downhill. Of course, I try not to P&G often, but even when DWL I can see the results on hills. Every day I drive to I-44, and there is a huge hill that I go up and down to get there. Going down I can get up to 60 (speed limit 50, but who cares, long uphill right after) then going up the hill I get down to 45 MPH. On the highway I just DWL because at those speeds and city traffic, there is no reason to P&G. Once at school, I can P&DFCO (automatic makes my DFCO last down to about 17 MPH) around the circle and receive great numbers, going from 27-23-27-stop.

What I'm getting at is that all vehicles are different, just play around with how you think it should be driven, do what feels best, try new techniques and see how they work out for your car. Don't do anything that makes you feel uncomfortable (EOC in auto for me) because then you will be a danger to other drivers.