Which mode for best interstate MPG??

Long distance interstate travel where constant speed is going to be met and kept?

I don't think it matters all that much. I never use "Power" mode as anything but a situational choice, for example merging on to said highway. So I wouldn't use it as a long term driving choice.

So that leaves ECO or Normal and I'm betting you wouldn't see much difference between either. If efficiency is your goal, why not just choose ECO? Whether it really is helping or not....constant cruising at 70-80 mph is constant cruising at 70-80 mph whether the ECO light is illuminated or not.

If you veer off the highway for breaks or lunch or get into an unexpected traffic jam, ECO might come into play. So I guess my answer is on a long highway drive my feeling is the difference between benefit with ECO or Normal would be minimal, but if you want to be sure your striving to maximize efficiency? Why not just choose ECO?

 

Easy question, ECO is the best mode, you can't use ev mode on the freeway, that's for parking lot dry I g, power mode is for getting on the freeway and be ding in traffic. Once your on the frwy just put it in ECO mode and cruise. In city or hwy drive in that's all I use.

 

I have just set ECO in my PiP and left it at that. If you want to maximize mileage 70-80 isn't going to cut it. On several road trip, I had gone the speed limit going out and typically got about 50 MPG or a bit more. I usually was more relaxed and just stuck in the right lane going 55-60 MPH on the return and got 60+ MPG! (This is both by fill ups and not by the dashboard readout.)

 

If using cruise control or AC, then ECO will be slightly better, because it allows a bit more slop in these functions. By slop, it will be less aggressive in holding right on the setpoints.

But if these functions are turned off, then the ECO/Normal/PWR choice becomes entirely a matter of personal preference. The buttons change only the user interface at the gas pedal, not anything within the propulsion system's function. Thus, 'best mode' becomes a matter of how the driver interacts with that user interface.

In theory, the same MPG is available in all three modes. But when common human frailties are factored in, most drivers, including slightly clumsy folks like me, will do best in ECO. But some will overcompensate for the filtering and slight delays it adds, and actually do better in Normal or PWR.

Use whatever mode works best for you.

 

Doesn't ECO mode also change how the AC and climate control is utilized?

I've never been uncomfortable either in the winter or summer using ECO with heat or AC, but I seem to remember reading that ECO tweaks that interface and how it is utilized in some manner.

 

Yes, i am already disabling ECO in the afternoons to get more A/C. It keeps up fine in the mornings, or after 20 miles.

 

I doubt you'll see any difference, ECO vs Normal. What will make a significant improvement is dialing down the speed, if possible.

 

At least until, and if, the AC can't keep you comfortable. IMHO, potential savings is not enough to worry about. The only sure way to maximize mpg is simply to drive slower. Unfortunately, since we drive 600 +/- miles per day, slowing from 70 to 60 would cost us 1-1.5 hours, not to mention forcing everyone, including 18-wheelers, to switch lanes to pass, creating potentially unsafe conditions. If I was able to manage 10 mpg more, which I think is doubtful, it would save about $5/day at $2.50/gal. For me, the potential savings just isn't worth the extra time and I don't feel comfortable going that slow in traffic. I will admit to being tempted to slow from 75 to 70 across Texas when the traffic was light last weekend, but dang, it already takes forever to cross Texas.

 

what kind of mpg do you get at 70-75? I,m in the mid 40,s.

 

Depends on temperature, winds, elevation changes:

Now that the car is on its second set of tires and properly maintained, I'm getting better at 40 mph. I suspect my high-speed may be slightly better too.

Bob Wilson

 

I also get mid-40's, but so much depends on the factors Bob mentioned. And since I'm usually loaded down on a trip driving those speeds, I don't pay much attention to what others claim or charts like Bob's because I never approach those numbers between fill-ups. If I was still working and had a daily commute, I'd probably be more interested in the different techniques to maximize mileage. I guess I could log some "per trip" numbers when we run up to New Jersey next week.

 

Thanks for the reply.
I drive mostly like a reg car. Not much babying.
I get avg. 40-45 winter 45-50 summer. VERY HAPPY WITH THAT!!!
And, I do NOT have LLR tires. These were 38$ apiece.

 

I've been running ECO mode the last 2 days and I think the MPG has improved. I say "think" because I'm driving new routes and new speeds and it seems like I'm getting 2-3 mpg more that I think I would have in normal mode, purely subjective. Now that I'm familiar with the Prius, ECO mode didn't seem as bad as when I first bought the car last July, still sluggish response though. But now I saw someone claim he gets his best MPG using PWR mode, go figure.

 

I really don't worry about the AC. I mean I use it if I feel I need it, whether I'm in ECO mode or Normal. Maybe it's just the environment I'm driving in most of the time but I seem to be OK with the AC and Heat regardless of what mode I happen to be in.

This might be primarily a difference between an Arizona summer...and a Pacific NW summer.

The only reason I brought it up was I seemed to remember that ECO mode tweaked how the climate control system works. But really? I can barely tell and I just use it as needed. I don't deprive myself of the luxury if it's a hot day....or a cold day and heat is needed.

 

I drove 75 to 85 from San Diego To Tampa. I got 38 mpg.
Nothing else gets 38 mpg at that speed.

 

I can't tell the difference either, though I'm in Georgia humidity at the moment. I only mentioned it because you did and folks seem to have different experiences. So many comments about the Prius are cautionary to let owners know what MIGHT happen and this seems to be one of those.

 

I managed 42 from Phoenix to Cocoa Beach. One would think I-10 would yield better results, but those 75 mph speed limits through Arizona/New Mexico and 80 through Texas are mpg killers for sure. What's amazing though is how little time those speeds save over the 2,000 miles. Using raw numbers, it takes 28.5 hrs at 70 mph, 26.6 at 75, 25.0 at 80 and 23.5 at 85. So the way I look at, over the course of the 2 nights/3 days we take to make the trip, the most we'd save is 5 hours. The unknown is how much higher the mpg would be at 70 and if it would be worth the extra time. Phoenix to Houston yielded 40.7 mpg while Houston to Cocoa Beach yielded 44.0. So using the difference for discussion purposes, I think we'd be talking about 4 gallons of gas ($10) for those 5 hours. The other factor is the availability of lodging. In our case, at 85 we'd get to Fort Stockton TX earlier and at 70 we'd have to stop sooner in Van Horn TX. Though neither alternative is particularly appealing , I'd much rather live with the mpg penalty just to avoid Van Horn. At 85, we could probably make it to San Antonio, but we still wouldn't go the rest of the way the next day, so I'm content with current speeds and mileage.

 

I've driven long distance on interstates for years mainly running from Pittsburgh to Naples straight through, 1170 miles.
You really don't make the time you think you do driving 70 plus mph. I've made the trip at the speed limits 70 mph and at a maximum of 65 mph and the difference is a whole forty five minutes. Due to better fuel mileage I also only need to stop for a gas once at 65 mph vs twice at 70 mph. As Bobs graph shows you are going to take one hell of a hit with fuel mileage. Five miles per gallon doesn't seem like much but in reality your looking at 55 more miles out of a tank of gas.

Something you really need to think about is how much money do you have burning a hole in your pocket right now? Something speed demons forget to factor in is the new paint you will need for the front bumper after a few years. The same formula that works for the needed HP needed to drive at 70 over 55 applies to road debris that strikes your front end. What harmlessly bounces off at 55-60 mph chips your paint at 70 mph. I learned this one from a buddy of mine that owns a body shop. He can tell just by looking at the bumper and hood whether the owner was hard on the car on the highway. I saw a 308 Ferrari at his shop and he asked me how many miles I thought it had on it and when is said north of 80K he laughed and said look at the odometer? The car had a little over 35K on the clock. The owner was one of those guys who liked to drive fast on the highway.

 

Couple higher speed with tailgating, perfect storm for hood damage.

Soon after getting our Prius, on a 90 kmh limit highway, I was getting dismayed by the lacklustre fuel economy. Traffic was light-to-nil, so I slowed down to 80, big improvement.

When it was two lanes no problem. When one lane, if someone came up in a rush, I'd speed up for a bit, then pull over, let them by, as soon as practical.