Cruise Control

I drive a 90 mile commute mainly on cruise control 65-75 mph 50-60mpg. Most of which is flat road. Sure I'd like to get more mpg but I'm happy with the results.

 

There's not a single answer for all situations and drivers. For many drivers it may save fuel in some situations, cost fuel in others and make no difference some of the time. Certainly, a blanket statement that CC costs fuel is wrong.

 

Cruise Control neither anticipates hills nor knows how long they are, so it does not speed up just before a hill, nor going downhill. It does not slow down right at the crest. All of which can help MPG.

In my case, I can drive (North South) 156 miles whilst only gaining (or losing) 100 feet of elevation, so hills are not a major concern and Cruise Control serves me well. (The highest point in MS is 880 feet, but it is not near me

You did not post a location (which will ALWAYS hamper our ability to advise you on any subject) so I have no clue how hilly your normal driving is.

 

It would be interesting to see a real world test on just how much difference this makes. Aside from irritating other drivers, I wonder if the difference needs to accumulate over a pretty long drive to be meaningful. Anyhow, I get excellent mileage just leaving the CC to handle things. I will say that RACC is a fuel waster, since it's constantly adjusting speed in traffic - but its OK on the open road.

 

it all depends on the situation...

 

I'm coming from a second gen Civic Hybrid and I'd concur: with that car the cruise seemed to have a negative impact.

I've found the 3rd gen Prius Cruise Control quite effective at keeping the mpg numbers high, at least as showing on Scan Gauge. Most anytime I activate it I'll see the numbers improve.

In cruise the car will aggressively stay in stealth mode. It'll also regen going down steeper grades, to maintain the set speed.

I use it quite a bit, any time traffic is light, at various speeds/conditions. Basically any time I may need to brake fast or negotiate a curve I for sure disengage it, but other than that...

 

My 9.8 mile daily work commute is about 7.5 miles interstate. I use cruise control 100% of that portion. All level ground and I wouldn't anticipate any real MPG loss. There's also a almost daily speed trap. Cruise control once set is effortless. Having the radar cruise control is a big plus.

 

My experience is that cruise control always lowers mileage. Finding the stealth mode is a moving target and CC does not understand it anyway. That being said, the advantages on a long trip, for me, outweigh the mileage loss.

 

I drive 105 miles a day over very hilly terrain. I use cruise control any time I am able to because I have found it is much better than me at regulating the amount of acceleration/deceleration needed to maintain a fairly consistent speed up and down hill. I have also found that my mpg goes up when I maintain a consistent speed. I generally have it set at between 62 and 69 mph and attain between 54 and 60 mpg (on the display) when I use CC.

 

cruise will maintain a fairly consistant speed on hills, which is why it costs mpg's. i find when i'm in cruise many others keep passing me and then slowing down. it's a pain in heavier traffic when i keep catching up to people.

 

I used cruise control and shifting between "N" and "D"+'resume' to do this:

An incredibly boring 'stunt' in my wife's 2010 thanks to cruse control.

BTW the cruise control light in our 2003 Prius burned out earlier this year.

Bob Wilson

 

I use CC as much as possible. In my case, one speeding ticket offsets any fuel savings.

 

On flat ground, I find that cruise control does a better job of keeping the engine near the stealth mode/eco level threshold than I can. That being said, I've very proactive in coasting into stops and turns and then manually accelerating back to cruising speed before reengaging the CC. I've only had my Prius for three months, but I have a higher MPG rating after every fill up so far and using CC when best has worked out well.

 

The average speed of 22 mph may have something to do with this.

 

Actually the minimum cruise control speed is 23 mph but it is unusable. The first dip in speed and it kicks out. So during the drive I was using 26-27 mph as the cruise control set speed. But even in a well planned route, there are stop lights, stop signs, and when I arrive at work, a parking lot. The average 22 mph is accurate because it does include stops and parking lots.

Bob Wilson

 

Tell us more, Bob! So you cruise at 26-27 mph, but what are the conditions that lead you to N? Do you resume from a stop or after getting back to speed? What is CC doing here that is different from your manual control?

 

The marathon drive was a 'stunt' and not something I recommend to anyone. I took pains to choose routes where I would not be blocking traffic and times when there was little or no traffic around. But during the stunt:

• Set cruise control to 26-27 mph and monitor energy flow display . . . drive the car
• When energy flow shows arrows from wheel to battery, shift into "N" -> the car will roll faster on downgrade
• When car speed approaches 26-27 mph in "N", shift into "D" and hit "resume" on cruise control -> car will continue at set speed
• When braking, shift into "D"

That is it,
Bob Wilson

ps. The physics behind it:

1. Cruise control speed -> minimizes aerodynamic drag; eases burden on operator and, efficiently moves car forward or ascending upgrades.
2. Shift "N" -> the car's potential energy is converted by the downgrade into kinetic energy, the most efficient transfer possible.
3. 26-27 mph -> provides enough margin to handle upgrades. With practice, 25 mph is possible but 24 mph is nearly impossible and 23 mph is not possible.