Hey guys ! We have 2 trips coming up this summer (600 miles and 1400 miles), these will be my first long distance with the Prius. Did anyone tested fuel economy using the cruise control in ECO vs NORMAL vs PWR ? Besides the fact that ECO mode will set the A/C "slow mode" (i.e. potential fuel saving) ? My 2 cents: Set it to PWR to get the best response time when passing ! Your thoughts ? Thanks !
Are you talking dynamic radar controlled cruise control? Or just regular cruise control? Because I don't think it really makes much difference which mode you are in once you've set a speed. The Prius is just going to maintain that speed as efficiently as it thinks is possible as long as the cruise control is statically engaged. Evidently ECO mode also changes some parameters as far as air conditioning goes, so it might be a little more economical if you are using the Air Conditioning on a long drive. Once you step on the accelerator to pass, the cruise control is disengaged....the acceleration is your input. I suppose if you have the vehicle set in POWER mode, you'll get the quicker response as always. I could be wrong, but I don't think it matters what mode your in once you've engaged cruise control....your basically in "Cruise Control" mode. Since I'm telling the Prius I want to maintain a set speed, on most long stretches where I'm using cruise control, I leave the vehicle in ECO mode, just incase. The maintained speed will be the same, and I've never felt uncomfortable or "hot" in the vehicle with the air conditioning being modified by ECO. So I don't really see much advantage in using any other mode. If I want to pass? Even in ECO the Prius will respond similarly, if I just press the accelerator pedal aggressively.
I did a little test on this with my cruise control. I drove the same mile of road so that I would have the same sort of inclines and declines. I did 55MPH in the Normal, ECO, and then the POWER mode. In Normal mode I was right at mid point of the instant MPG bar and on decline would go up to 60ish MPG for the mile. In ECO I was slightly over the mid point and on decline would go to 75ishMPG. In Power mode I was just below the mid point and it would go up to 60ish MPG on the decline. I'm not sure why the declines are different since it should be coasting? And these declines were very mild. Not like a steep hill but you could tell there was a slope. This of course is no where near scientific.
Keep in mind you can defeat the purpose of ECO if you lower the temp dial to achieve the cooling you really want. ECO is not a miracle cure to get better mileage. All it does is dull the throttle responses and reduce the a/c output - both which can be overcome and therefore defeated. I never use it. I use mostly normal, but sometime will use PWR mode to liven up the driving experience a bit. Amazingly, I sometimes get better mileage in PWR mode. I think it's due to all the mini power/glides I end up doing with frequent jabs of the throttle during my commute.
Using CC will only help if you tend to go faster without using it. If you drive in a hilly area, CC can use more because it will maintain your speed going up the hill, but will also save as you go down the other side while it try to keep to your set speed. If you're the type that speeds a lot, going up the hill and not coasting down the side, CC may help you get higher mileage. I personally use it to maintain an even speed and avoid speeding tickets!
I'm finding it does pretty good, most situation. I've taken to using quite a bit, will shut down when a steep grade or slow down is approaching. I have a ScanGauge, and almost invariably the instant mpg improves when I enable CC. The only downside is it's somewhat slavish adherance to the set speed. Still, all-in-all...
I have a 104-mile/day round-trip commute and have found I do better mpg-wise using cruise control even though it's an extremely hilly ride. Since I'm driving interstates with moderate traffic at 55 or 65 mph speed limits and everybody drives well over the speed limit, especially when it's 55mph, I need to maintain speed and not be speeding up and slowing down in order to accommodate ascents and descents. I also mainly use PWR, especially if I have to pass cars or climb hills from a stop. I can't stand the sluggish feel of ECO. I really haven't found that ECO saves anything in mpg over PWR.
