Speeds to avoid?

[tovli]

I can't find the chart I was viewing yesterday, but I came away from it thinking I should avoid 41 to 46 mph to get the best overall gas mileage.

Since I frequently drive in 40 and 45mph speed limit zones, I was thinking I should do 40 in the 40 zone and 47 in the 45 zone.

Yesterday, when driving these stretches of road, my indicated MPG seemed to stay slightly above 50 at any steady speed from 40 to 47.

Is there any speed zone that should be avoided?

[JimboK]

Assuming steady speeds, the Prius' fuel economy decreases more or less linearly with speed above 20 MPH. The only blip in that line is at 40-41 MPH, below which the car will run on electric only, but not above. So you'll do better by staying at or below 40, assuming traffic and your own tolerance for driving below the speed limit allow. See this for more.

[donee]

Hi All,

I agree with JimboK, but be aware that these graphs do not have the impact of a newly realized operational method called Super Highway Mode. With SHM, temps between 65 and 85, no wind and a level road without stops, one should be able to get near 70 mpg at 53 mph, and 1280 RPM, after a battery charge-up to 60 % SOC. This is a steady state engine driven mode. I guess this is the capability of the Atkinson engine to run at low powers efficiently, and the wide gearing range of the ECVT to match the engine when its running that slow while the car is relatively fast that is responsible for this.

Below about 48 mph, engine speed becomes too slow at a steady RPM for it to operate efficiently in SHM, and the car has to switch back and forth between battery, battery assisted egnine and engine powered. When in pure battery mode, the car is wasting energy to keep the engine turning, but unfired above 41 mph.

Below 40 mph, pulse and glide works great yielding similar to better mileage than SHM, depending on stops and traffic going at the wrong speed at the wrong portion of the cycle.

[hyo silver]

I try to avoid speeds greater than 10% over the posted limit. Most of the time.

[Shawn Clark]

It feels less efficient/like it is loafing/lugging and shouldn't even be on from 42 until ~50. I try to stay out of that band as I've gotten much better indicated gas mileage above and below.

[Bob64]

88 miles per hour. You wouldn't want those 1.21 jiggawatt-hours to get used up.

[KK6PD]

767.58 mph

Damn Noise Ordinances

KK6PD

[auricchio]

Remain below the speed of light. There are, however distinct advantages and disadvantages when traveling at light speed:

Advantage 1: Whenever you approach a red traffic light, it always appears green.
Advantage 2: You can't see a police car's red light in your mirror.
Disadvantage 1: Flashing your high beams at a car in front does no good.
Disadvantage 2: You can't see the reflectors in the road.

[Mjolinor]

Originally Posted by auricchio

Remain below the speed of light. There are, however distinct advantages and disadvantages when traveling at light speed:

Advantage 1: Whenever you approach a red traffic light, it always appears green.
Advantage 2: You can't see a police car's red light in your mirror.
Disadvantage 1: Flashing your high beams at a car in front does no good.
Disadvantage 2: You can't see the reflectors in the road.

I suspect you could also achieve maximum mass to energy transfer and vice versa. Or something like that.

[ystasino]

Originally Posted by tovli

I can't find the chart I was viewing yesterday, but I came away from it thinking I should avoid 41 to 46 mph to get the best overall gas mileage.

Since I frequently drive in 40 and 45mph speed limit zones, I was thinking I should do 40 in the 40 zone and 47 in the 45 zone.

Yesterday, when driving these stretches of road, my indicated MPG seemed to stay slightly above 50 at any steady speed from 40 to 47.

Is there any speed zone that should be avoided?

Low Speeds:
My experience is that the best efficiency is at roads at with moderate uphills that allow sufficient pedal pressure to maintain speeds between 20-30 mph followed by very modest downhills that allow gliding for as long as possible. Back when I cared about efficiency I wouldn't turn on the heating. During winter-time that made a huge difference in the city: without heating at 72F I would get about 45-50 mpg with heating it has come down between 35-40 mpg. Thankfully I mostly drive highway now; A/C does not have such a huge impact there.

High Speeds:
Due to my Greek upbringing and the lack of patience that confers, I have succumbed to traveling with cruise control at around 68 mph. Back in the days that I cared about efficiency I had found that 52-57 mph with cruise control and AC at 72F at summertime would easily get me ~55 mpg.

My OEM tires are always at 44 psi following the great recommendations of people here and they look like they have really good tread left in them