Highway MPGs Using DRCC: 63.4 at 60+ mph

It would only have made about 1-2 mpg difference.

 

What were your tire pressures? Did you use the AC? If you did use AC were you in the ECO Mode? Did you use 3 bars the whole distance? I find on the freeway I sometimes need to drop down to 2 or even 1 depending on traffic conditions.

I checked my mileage from here to Portland on I 84 using DRCC, about 200 miles each way. I had my DRCC set at 65 to 70 except the 20 miles or so when I'm near Portland then I drop it to 60. Last trip was about a week ago, AC on most of the trip, ECO mode, tires at 48 lbs. There are quite a few hills, no mountains. To many hills to be very sucessful following trucks as you were. The wind was blowing 30 Knots or so and I only got 46 MPG (displayed) going West. Coming back I over the same route I had a tail wind and managed 53 MPG displayed. Previous tests indicate my displayed mileage is about 2 to 2 1/2 MPG better than actual MPG. I think my Gen2 would have gotten about the same mileage.

So maybe your trick with the trucks works pretty well, your mileage is certainly better than mine. But I don't think it will work around here because the elevation changes slow the trucks enough to hurt mileage.

I'll be going over the same route again next month and I'll try to find some cooperative trucks and see what happens, maybe the wind won't be blowing and I can get some better numbers.

 

Are your figures for round trip or one way? Definitely useful and interesting info but one way never tells the whole story.

Tumbleweed: I've driven that route. Is the wind ever not blowing?

 

For starters, doing the bleed-off-on-uphills and get it back on
the downside *is* an efficient way to drive, and every trucker
knows this [whether they actually practice it or not, subject to
their engine power]. But more importantly, even if you had DRCC
on the "long" setting which the manual says is about 160 feet, you
were less than 2 seconds behind the truck at 88 feet per second,
and therefore drafting trucks at a distance that the truck drivers
*really* don't want you to be at. My outside voice at this point
wants to say "knock it off", but for the most part you're only
endangering yourself in that situation. And setting a bad example
to those around you.
.
Try this next time: mimic what the truck *would* be doing over
the same terrain, by locking your foot at a particular HSI demand
and letting things play themselves out but keeping an actual
*safe* following distance from other traffic. Your results
will likely be similar, but I'd be interested in which way
the long-term delta is -- on one hand you maybe get a bit of
aerodynamic help by the tailgating trick, but on the other you
don't have to react instantly to any change made by the vehicle
ahead and can thus ride right in your own sweet spot more
effectively by leaving a nice big open "cell" to play in.
.
Sorry, DRCC and LKA are *not* substitutes for 100% aware driving.
Not even close. Maybe when a tire cap comes in through your
windshield, you'll understand.
.
_H*

 

Hobbit, I share your concern about adequate following distances but the owner's manual is a bit misleading on that point. The 3 bars = 160 foot distance is only at 50 MPH. The bars are more closely related to time, 1 bar = 1 second, 2 bars = 2 seconds, and 3 bars = 3 seconds. It's not exact but it seems very close, I've checked it a number of times at speeds from about 40 up to 80 MPH. 3 bars equal to 3 seconds also means that the 160 feet at 50 MPH is wrong, it should be 220 feet. Perhaps others who use this system could confirm my observations, please? I would speculate that the software that controls the system may have been changed after the manual was written.

The DRCC also seems to pay very close attention to the speed differential. If the car in front slows rapidly or if you approach a slower vehicle rapidly it will brake rather sharply to compensate and maintain a proper distance. On the other hand if the car in front is accelerating away from you, such as when someone passes and cuts in front, the DRCC may not slow you down at all, depending on how close it is, and just allow the distance to open up.

But like any other vehicle control system it needs to be monitored because it could make a mistake. After 6500 miles, mostly on the freeway, mine has not gotten anything wrong yet but I watch it closely and I always will.

 

Good to know about the DRCC. Unfortunately the highway I take to work doesnt allow trucks, and is very hilly, so I tend not to use it, but on long trips like the one I'm about to take tonight, I will definitely be more inclined (pun intended) to use it even uphill.

 

Most of the time it is Roy, especially in the spring. Good place for wind turbines though.

 

Let's be realistic. That distance is an eternity behind a truck or even a car on many roads. You will have cars weaving in between you and the truck at that distance. There is little for the trucker to worry about with you at that distance. The truck won't out brake you. And they don't seem to have trouble changing lanes right in front of you when you are passing... When you get locked in traffic there will be several cars between you and the truck at that distance.

One should be more concerned about following sporty vehicles with short stopping distances. Whenever I have to brake hard I'm usually watching my rear view mirror to determine if I'm going to have to instead take evasive maneuvers to avoid being run over. There's nothing quite like the thrill of seeing an 18 wheeler barreling down a hill at you smoking his tires because some jackass stopped at the bottom of a hill in the highway. And while you ponder taking the ditch, having the car behind you beat you there...boxing you in so that he can avoid being run over. Leaves an impression even when the trucker does manage to shut it down a foot off your bumper.

Where folks get into real trouble with truckers is side-by-side driving, especially in their blind spots. It gives them no room to maneuver and they might not be aware of you. The other problem is folks that pull right in front of them. The trucks need more room to stop.

 

Just FYI,
The 160 feet distance is at slow speed, say 30 mph.
The set distance is automatically increased as speeding up, say 250 feet or more at 60 mph.

Ken@Japan

 

Heck,

I'm glad to hear that you've gotten your car back (again, and again, and...oh yeah...again). Hopefully the fourth time is a charm.

 

Wayne Gerdes (Xcel) over at CleanMPG was telling me that was what most people were seeing in real world driving.

Think about it the tires are only slightly wider (two sizes) than stock. Has the aero number changed? , weight changed? Nope, only the road friction from the slightly larger tire contact patch. I'd bet the weight difference between the 17's and the 15's isn't as much as most people think. Remember the 15's also have hubcaps added on for a little better aero numbers.

Now on the Prius the change also effects the rpms by increasing them on the V. The 15's are 832.6 rotations per mile verses with the 17's 845.1 rotations per mile. That is 1.5% difference to the bad.
So if your running 1500 rpms with the 15's the V with the 17's would be running 1,522.5 rpms at the exact same speed. Not much but it would be burning slightly more gas. Add that in with the increased road friction and there is your 1-2 mpg.

I think Toyota said 4 mpg to cover their asses. Remember people who buy the V's are probably in general driving them a little more spiritedly than the average Prius owner.

 

wow! That is not fair! I have fought like crazy to achieve 55mpg on the MID, then it just takes getting in a hurry once to drop that to 50mpg. LOL I need to check my tire pressure maybe.. haha. I drove my parent's Prius yesterday and today and I think my dad had the pressure maxed on the tires. lol.. rode kind of rough. He has been getting 55 consistently in his gen2.

 

have to say that Hobbit makes valid points about safety, but i am at a complete loss as to where we could exercise this. where i live, i cant maintain a following distance of 150 feet even if i wanted to (and i do!!).

i can at times and the busier the traffic the greater the following distance i want. but on a busy freeway, i have a constant stream of people cutting in front of me. i ignore them and continue on since its normal for me to vary speed from 50 to 65 mph depending on traffic to keep from having to hit my brakes