Cruise control and MPG.

hang on, you used your foot in one direction, and the cc in the other?

 

i think you need to do a round trip with each

 

But that isn't how a Prius works, it doesn't use any gas to slow the car down on downhills. Normally, it does a bit of electric regenerative braking, putting some electric charge into the traction battery, with no eCVT 'downshift' at all. Only when that battery is full (or nearly so) does it use any engine braking, and that also uses no gas. Nearly all modern cars have DFCO, deceleration fuel cutoff.

The only "more gas" needed is to regain speed that was previously scrubbed.

Of there was any breeze at all, even just a few mph, then this was invalid. Do both modes in both directions, for 2 round trips. And even this will be susceptible to any temperature or wind changes during the test.

CC shouldn't kill mpg. It should do better than the worst drivers, but not as well as the best drivers.

 

Even better: "Is cruise control worth $43 a year?"

 

THIS. The cruise control's primary purpose is to maintain speed, mostly without regard to fuel efficiency.

The test described here is invalid for a few reasons: The trip was too short and the route was not identical (going different directions does not count).

 

Wind may not even be the biggest factor rendering the results of this "test" in opposite directions invalid. Going each way, those hills are most likely of different lengths and grades depending on the direction of the approach. There's a large difference between the mpg involving steeper climbs with longer gradual downhills and longer gradual uphills with steeper descents. Because of that, the tests were not conducted on the same course.

Round trip on the same course in the same weather conditions is the closest the average person can get to a valid test.

 

That is not a particularly valid question due to fuzzy math. I know of no Prius that is even capable of using the cruise control 100% of the time. Most drivers I know don't use it 100% of the time for their long distance driving. They use the cruise control when travelling on the highway but turn it off and rely on their foot when climbing hills. The key is to avoid having the car downshift to a climbing gear or its CVT equivalent that the cruise control will require it to do. That climbing gear does drastically reduce the mpg but it only happens when climbing, not descending. Cruise control is resumed after the crest of the hill is achieved. Besides, it can make it uncomfortably noisy in the cabin.

That $43 figure is going to be a lot lower. Even at that number, though, in our case it's worth it. We use it judiciously while taking trips of 100 to 250 miles each way on the open highway four to six times a month. At least once a year we take a trip much longer than that across multiple states.

 

Yes. When we bought it in early 2016 the battery was already acting up. The Prolong system has helped it a lot but it's still been living on borrowed time. The overall average has now dropped by 0.4 since the beginning of this year so I'm sure it's on its way out. I just have to decide if I'm going to put in a new battery or replace the car altogether.

As for as the "yikes" part of your response, low 43 is the average for a 2008 at both Fuelly and fueleconomy.gov. For every 45 out there there is one who reported 41. Considering mine is a touring model (little bigger tires; a little less mpg than regular model) and it spends a lot of time between 70 and 80 mph I'm not too upset about it. It's still better than anything else that age.

 

True, but you are arguing my point. As you state, the actual cost is even less when you down-rate by usage. However, the very fact that it is used at all means that is worth the cost. I only use it for long trips. But when I do use it... ...boy am I glad that it is there!

 

Good god kid. Where the hell are your priorities? Your breaking down like a couple of miles per gallon. Who cares? You should be figuring out how to get layed.

 

In my experience of using cruise at all moments of driving above 25mpg (because the cruise doesn’t work below this) and adjusting speed with the cruise control itself, I have noticeably increased mpg on my vehicle. I am talking 10+ mpg more efficient by using cruise control. I live in Colorado