how do y'all get high mpg at highway speeds?

While not a ‘c’, I generally do 65-70 mph and get 50 mpg in our 2010. Mostly flat with minimal grade change except for one pass crossing each day, which eats into the mpg average.

On the current tank I have 303 miles and am at 50.6 mpg.

Not bad for almost 10 years old and 200 k miles.

 

I think your experience is pretty typical for C owners. In my 2012, it seems that 70-72mph or so is the cutoff between getting over or under 50 mpg. Small differences after that would be due to terrain, climate, traffic, etc. At highway speeds its more about the basic effeciency of the ICE, your driving habits, and the other external factors mentioned, than it is about hybrid technology.

 

This car absolutely loves 55 mph. Somewhere on this site, there's a chart that shows at what speed you'll get what MPG. It's pretty nice.

 

Addressing only the question asked in the title of your thread............
You don't.
You can't change the laws of physics.

And you can't stop people from exaggerating from time to time.

 

I have a 45-50 mile journey to work which is 75% freeway. It's slightly net-downhill outbound and slightly net-uphill on the return trip, mostly flat with a small freeway hill section. Recently I hit a new "best" for a single gas tank (56.5mpg). The behaviors I concentrated on for this gas tank were:
- accelerate from 0 using gas, staying out of the PWR range, but not trying to stay within EV as I was previously
- cruise on EV if possible (when the flow of traffic on city streets is under 40mph)
- cruise at 65mph on the freeway as much as possible (occasionally going up to 72 in the carpool lane, in order to move over into the next lane temporarily, getting out of the way of people in a hurry behind me)

The difference between the "best" tank and the subsequent tank (which was 53.9mpg) was that I was less disciplined about sticking to 65 on the freeway. 70-75 is definitely what left-lane drivers want on the freeways here, but the Prius C definitely makes you pay for it in mpg. I don't do much city driving but over the last 10 tanks I've averaged 53.2mpg.

 

This was on my mind right away, pretty telling:



Thank you to @bwilson4web , for original post:

Updated MPG vs MPH chart | PriusChat

 

With a performance seloniod I was able to get better acceleration performance and in return stepping less harder and shorter was possible.

I use my internal combustion engine (ICE) to pull away from a stop and accelerate to cruising speed, if I am in traffic or in the city then I ICE up to cruise and switch over to my electric motor (EM) which is nicely doable under the speed of 55km on level roads and sustainable for up to more then 2km, the less the speed the longer you can sustain it, basic physics of resistance. But the range gliding is not important since in the city you get stopped by traffic within that range anyways.
The trick is to keep that battery charged for your glides. So when you are stopped and waiting for the light or just cruising around in dead slow traffic you will have juice and not using the ICE too charge while at a total standstill. ( worst for millage) but there is one static ICE engine run that I world do which I will talk about later.
So now the light turns green what do you do?
I know most will go EM until your ICE kicks in. STOP! Dont do that if you want millage.
Say you use your EM for the acceleration which its not very good at doing after 25km/h by the way, you are burning all your battery capacity. And as soon as you get to speed limit you most probably have to stop pretty soon. So the question is; how on earth are you going to recover that battery capacity? Your ICE was just running after you past the 30km/h speed which means its been only charging the battery for less then 1min before you had to stop. And i can promise you that your regeneration braking is less then adequate to recover what you used to get up to speed.
You get yourself into a vicious cycle of running low and battery, having to charge at a standstill and not getting good millage.
My battery seldom go under the half way line.
My next post I'll write about how i keep it charged. Stay posted! Got to go to my PhD seminar.
I'm Canadian by the way! Just in Taiwan right now with the C hence my user name!

 

Every car hits an aerodynamic wall at popular USA highway speeds. The prius just has more potential savings to lose.

 

Part 2

Highway! This is the most difficult to achieve. Our engine will do around 45 mpg or 5.2l/ 100km on paper highway. In the real world factor in wind, drag, incline, tire pressure and moisture you are looking at 43 on a good day. So how do we get close to that value or go nuts and do our 70+ combined?
The key is to let it be for that 60mph+ part of highway speed and pull every drop of efficiency before you get there. For example utilizing the ICE and EM characteristics in the city and sub 60mph speed, making them do what they are good at as i mentioned earlier.
Further way to do it is to install parts to improve the engine efficiency, with the new seloniod I installed I was able to improve not only a great deal of efficiency in the city but also I was able to get up to highway speeds more efficiently.

Put together all the influences and driving technique and given that it is not 100% Highway driving we were able to achieve 70 MPG+ numbers.

This is the bottom line honest truth of how these numbers come to be, anybody who tells you they can do 60 miles or 70 miles per gallon on full highway driving is not possible.

If they reset there trip domitor and fuel economy meter while cruising at highway speeds 70mph+, for however long they like as long as they are using the ICE only and stay above "reasonable" higher speed and read the mpg they will never get more then 55mpg even if they cheat. Just look at Mendel chart and it will be very clear that you need to capitalize on your city driving. From 50mph onwards the efficiency is just not a straight line anymore.
Look at Michael's post, he too mentioned city driving of 25% too to make up for the lost mpg on the highway. Not much of it but it still helps that sub 55mpg on the highway.
The time I'll burn ICE at a standstill is 1st thing in the moring or knowing I'll be climbing hard right off the bat. This not only protects the engine but also protects my battery. Engine gets a head start not having to Output power when it's cold and also batteries don't get over drained waiting for the engine to heat up so the computer would let the engine produce driving power.

 

Do not use cruise control and stay under 70 mph if flat or uphill, go faster on the downhills without using gas

 

"Highway speed" means drastically different things to different people in different contexts.

Some of us drove more than two decades under the National 55 MPH Speed Limit. Poor winding roads were commonly marked down to 50 or even 45, and a number of them still are, so those speeds are still considered "highway speed".

 

I think you have to learn how to drive all over again. If you follow the flow graph on one of the driving screens about "braking" "acceleration" "cruising" and ....try... to keep the throttle out of the ....red... your mileage per gallon will go up....

I know it is a small thing, but minimal use of the A/C also will that case significantly....

Questions to ask yourself....Do you "have" to go up a grade with your foot to the gas pedal to the floor? Can you live with arriving a the top of that grade a few seconds longer? Can I handle an 80 degree ride with the windows down, as opposed to a 75 degree ride with the A/C on?

Food for thought....

 

Don't open the windows, at least not much. Wind drag is an mpg killer. Better to keep the A/C on, but push the set temperature up as high as comfortable.

 

I contemplated a lot regarding the extra mile on a tank of gas by going hyper ECO, I live in tropical climate. When I had to do comparison test just because previous stats were with the AC off during spring time, I had to endure the heat for the later sample testing during the summer.
I think our cars are the most efficient ICE set up out there! Even with AC blasting and dead still grid lock we can still manage to pull off 20+km/L.
Now days I still look for that all time high "MPG" but I also want to be comfortable when I am traveling. The sight of 30km/L+ is really rewarding and satisfying!
I think there will always be a fight within all us hybrid pilots!

 

The speed range between 50-65 mph is where one can get the best MPG in range of 55-61. Speed above 65 mph our car starts to loose MPG, at 75 mph i get only 42-43 MPG. Drive the car as you like you can still get 50-55 MPG, I enjoy the ride instead of making the car drive me

 

In the words of Sammy Hagar, I can't drive 55... but my car sure does love it when I do.

 

I managed 55 in my 2012 in my last tank I do about 80-90% freeway but I drive at around 60-62mph. its very hilly here so I have to use gain some speed on the downhill like a semi and slowly bleed it off going up the long up hills. id do 55 but I find managing that speed alot harder then 60-62 when it comes to bleeding speed up the long inclines we have. I actully enjoy goin 60-62 instead of a faster speed as it rudeces road and wind noise alot. if you live in a flatter area then me you could probably manage getting higher mpg even easier then I do. id say give it a try on your next highway communte going 65 vs 75 and you can weigh if the mpg savings is worth what ever few extra mins you save

 

1. Get behind a large slow-moving truck, and stay behind the truck. I do not mean drafting it.
2. Have LRR tires that are pumped up to higher than recommended.
3. Keep the windows up.
All of the above will help with highway driving.