MPG vs "Level" Speed

[FrugalFloyd]

Here's the mileage to speed chart for my SE-R. All values obtained in 6th gear.


And here's the corresponding chart for my xB. There's an error in the data. The first bar should be 70 mph, not 72 mph. Note the 30 mph value drops off the straight line. That's because it's a 4th gear value and all the others were obtained in 5th gear.

[GasSavers_maximilian]

I hope you don't mind, but I find xy graphs easier to interpret. Your graph is a lot more linear than mine. Interesting. The books I've read always show a local maximum at 35 mph, and then a global maximum in the 45-50 mph area. So much for that. Thanks for the info!

[FrugalFloyd]

Yes, I like x-y graphs, too, but I hadn't figured out how to create them in Excel by my previous post. I looked up how to make them on the Internet, and can do it now.

Pulse and glide creates another line about 5 mpg higher for each speed between 30 and 55 mph. However, there's so much variability, the P&G line can be 10 or 15 mpg better at the lower speeds, and the actual speeds to achieve P&G averages are 10-20 mph deltas.

[GasSavers_maximilian]

Once you get away from anything basic the number of possible combinations sure explodes fast. Where are you using for your testing? Finding a straight and level spot here was tough.

[FrugalFloyd]

The data points are optimal ones. If I hit traffic, or drive the cars on different roads, the mileage data almost always go down. I have a country road test loop that's a frontage road to a freeway. It rarely has traffic on it, and is reasonably level, since it's at sea level. I run it both directions, and get a ten mile drive that's pretty consistent. I used to drive the loop twice for a 20 mile drive with slightly higher mileages, but 10 miles is enough to show the differences of different P&G techniques, and different cruise control speeds. When I do the high speed tests (55 mph and over), I do them on the freeway that parallels the frontage road.

I coast as much as possible at the end of my frontage road drives, and my mpg figures look higher as a result. When I do the high speed drives, I get the car up to 55 mph, reset the Scangauge's current trip data, and record the mileage 1/4 mile before I take the exit to turn around. I get better highway mileage driving southbound, so I average high speed mileage going both directions.

[FrugalFloyd]

I gathered some more data today with my Sentra, using cruise control in different gears, and a low speed P&G average. Here's the chart.

[GasSavers_maximilian]

The speed you show for P&G is the average travel speed, right? Just checking. That really helps put things into perspective. We need a data logging system really badly.

[FrugalFloyd]

Yes, that P&G speed is the average between 25 mph and 40 mph, which is usually in the 28-30 mph range, depending on the downhills, length of coasting, etc.

There's a high speed P&G blip at about 46 mph on my Scion, and about 55 mph on the Sentra, where the mpg for each is about 5 mpg higher than the cruising mpg for the same average speed. On a good day, I've been able to coax 59 mpg out of the Scion over 165 miles, and I averaged 51.5 mpg over 1213 miles from Gallup NM back to the Bay Area in the Scion. That was done with a lot of coasting down long downhills that brought my mileage up. On those long downhills, I can pulse for 5-8 seconds, and coast for minutes.

[shatto]

All of which is why I use average MPG calculations. That, and I don't have a ScanGauge.

Max... Am I the only person at gassavers who doesn't know what vehicle you are talking about?

[GasSavers_maximilian]

Good point. I only have the one in the garage (on the left), so I guess I have been taking the context for granted. It's my 2008 Hyundai Accent, Gold Digger Repellent.