MPG at Highway Speeds (65+)

this what i got.

 

Just a guess, Ghosteh was saying that 60-65 mph is a compromise value he is happy with when he considers other drivers on the road, extra time driving, and fuel economy.

 

I always use the power mode. I really like the extra power getting the car at a certain speed and coming off the line.
Most of my driving is freeway.
I get (manually calculated) 43 at worst and 45.7 at best in cold months which isn't that cold in Arizona Dec-Feb calculations and the summer I think I was averaging around 46. Best milage I got was just under 49 but that was driving regular mode when I first got the car.
This is for a third generation Prius.

I just bought a 2012 and have not calcuated first tank yet.

 

Well, the 'sweet spot' is going to vary, and I've already seen that. I've repeated the trip that I documented in the photo in my sig, and my mileage was in the mid 50's. Same speed, same route, same weights. The only difference was higher tire presures (which should have helped) and a lack of a healthy tailwind. The wind, I feel, is the greatest variable... at least for me. If you're running into a strong headwind or its hitting you from the side, it really seems to effect your mileage. My former 'sweet spot' that was 60-65 was probably more like 50-55 on the last trip. However, I'm not going to drive on the interstate at 55mph just to get 5-8mpg more. Next time, I might repeat the trip and again get 60+mpg.

 

First assuming you inflated your tires to the max, drive with the windows up, are gentle on the accelerator AND are very conservative with the brakes, 50 mpg is reasonable to expect up to 65 mph. To maximze your mileage I would stay in the right lane. This also assumes you are using the "small" tires.

If you exceed 75 mph don't expect more than 45 mpg. Gerry

 

Just finished a 3200 mile trip to Fl to wade with the Manatees (for free), average was 53.3 overall, @ 62 I was always in the 60's and @ 63 it dropped into the 50's.
Weird... from Stuart (Fl) down to WPB mileage dropped to the high 40's, both directions and headed up after getting out of southern Fl, lot's of 1/2 and 3/4 ton trucks with one passenger, must be a case of priorities?

 

This is about the best I can do so far. I know the mileage is not that much. I think I ended up 49.9 after 250 miles. I accept my fate due to my wheels and am still very happy

 

I take back my earlier post. After a new set of Michelin Energy Saver A/S tires pumped up to 38F/36R, I got 53.4 on a 230 mile trip at 65-70mph. A/C was on 70F, eco, as well.

So if you are not getting 50 mpg at 65 mph, either:

1) You have a mechanical problem (e.g. e-brake adjusted too tight, weak HV battery, etc)
2) Non-LRR tires
3) Very hilly terrain and/or bad weather conditions.

 

I just got back from a 1962.8 miles marathlon round trip via I-70 super highway trip from St. Louis Missouri to Washington DC Metro Area and back again. I was travelling as high as 81 mph and most of the time my 2010 Prius was travelling aound 75 mph to 77 mph (as tracked by my Garmin GPS unit) when I was on I-70 which has posted speed limit of 70 mph most of the way. I would have gone closer to 65 mph behind the tractor trailers in the slow lane on I-70 but I had to make each trip in a day. I had a funeral to go to in St. Louis on Friday and then I had to return to Washington DC to attend another funeral on Sunday - so I had to trade fuel efficiency for time. The tire pressure for my stock Yokohama Avid S33D were set to 38 psi front and 36 psi rear. The driving temperature was over 60 F so I remove all my grill blocking. On the way to St Louis - I had a sunny weather with dry roads but it was cool enough so I didn't need to turn on the AC. On the way back to DC - It rained all day long and the roads were wet all the time ( I also had to use the defroster to clear the windshield several time). Over the +14 hours in each direction, I took multiple breaks to rest and I used cruise control most of the time. I had to do several refuelings - This 1962.8 mile round trip required 40.263 gallons of 87 octane gasoline ( average price was about $3.90 per gallon). My fuel efficiency for this trip of 48.75 mpg (calculated average over several fill ups) was composed of about 95% highway driving and 5% city driving so -- which is on par with EPA highway estimates but not on par with my +60 mpg hypermiled tanks I normally get from my 16 mile commutes. A tank by tank review of this road trip is available at cleanmpg.com's mileage log under HyperDrive1. A record of each tank used for this trip and and a fuel efficiency chart (which takes nose dives for this marathlon road trip) is available.

 

Agree 100%
Have driven my 2012 Five for five weeks now in daily commute (28.8 mi each direction) and have been consistently seeing 50mpg instantaneous at 65mph on flat stretches with no head or tailwind present.
It's surprising that wind can effect mpg so drastically, have seen +/- 5mpg depending on wind direction/velocity.

 

The best I got was last summer on a 4-hour highway round trip. Both ways were on the same route on a warm sunny summer day. Speed was set on cruise control at 110km/62Mph. It was a 100% highway trip with no slow down or stops.
Average was 4.7L/100Km or equals to almost 50 MPG.

It is so far off from the Toyota brochure's 4.0L/100km (71 Mpg). There numbers are unrealistic in the real driving world but I am still happy with what I got.

 

I recently did a round trip from NYC to DC in I 95, some 300 miles. Weather was dry, 60F, traffic was light to moderate, no climate control. I stayed between 55 and 65 mph. I stayed mostly in the right lane. I slowed a bit going into hills, and went as high as 70 mph on the down side. I averaged 62 mpg for the whole trip. Very little city driving. But you have to work at it to get that. It isn't that hard to get only 50. If you're the type that is in a hurry and always floors it to stay up to the bumper of the car in front of you, then you'll get 45 or a little less.

 

Was that 62 mpg via the FCD or an actual miles/gallons?

 

I've noticed the type of interstate makes a big difference. If I am in a concrete canyon I can cruise >70mph and maintain >50mpg with no issues. I suppose the wind factor just boosts the aero. Put a tractor-trailer on the right with the wall on the left and you are looking at 80mpg plus.

 

With our Prius on Interstate Hwy 5 in Washington from Kelso / Lonview area MP# 36 up to Lacy WA, MP# 111, posted limit for most of the ride is 70 mph, some areas are 60 mph.

With temps in low 60's,dry roads with 500 lbs in the
car, myself, wife and baggage we average 55-57 mpg
on the mpg gauge for about 52-54 mpg calculated

Speeds from 60 to 72 mph. Tires are 195x65x15 Michelin
Energy Savers with 44 psi in all four tires.

 

Just did a trip from NH to Fl and back total 1650miles 53.3 average...

@ 62mph or below 62mpg or better, @ above 62mph a sharp decrease, 52-53, but above 70mph into the 40mpg range.

40pounds of air in the tires, an "11" package 4 with 1,200 miles total, K&N air filter, TRD rear sway bar (highway comfort), weird, 1/3 down Fl the mileage, even at less then 62 was in the low 40's, inched back up after getting more north, (heat saturation in the main batteries?)

In every day driving I sit around 60mpg, got a gen 2 and it's(the gen 3) 10mpg better, err more friendly by 10mpg, err, I can only laugh at pickup drivers...

I have an "11" F-250 for towing horses and hay, but I still laugh.

 

I drive 140 km everyday for work, 90% on the highway.

I get 3.8 L/100 km (62 MPG).

The only special thing I do is driving at 90 km/h (56 mph) on cruise control.

People always tell me that it's ridiculous, that it's way too slow.

Well yeah, it's slower, but damn those people, just do the simple calculations.
Considering the area where there is trafic and everybody has to go slower, it adds about 3 more minutes to my commute than if I was going at 100 km/h (60 mph).

Of course, if I did a very long trip, I might go faster to save time, but for me, 90 km/h on the highway is the way to go.

 

I can take 2 different routes to work. One is via HOV lane the other is about 2 miles longer. I base my decision on if the HOV lane will be slower or not. If I know it's going to be slower (leaving at a later time), I will take it. This way I know I can average about 60 MPG.

If I leave early (go to company gym before work), I will take the longer route, because the HOV is less congested and the speeds are a lot higher, so I only get 50 - 54 MPG. I can also get around 58 - 60 MPG on the longer route. But, if I take the longer route when I leave later there is likely to be a more congestion, so that's why I don't take it all the time.

A lot of times going home I will take the longer route (5 min difference) and have gotten 63 - 66 MPG. This is due to two factors. Less hills and the ability to safely draft larger vehicles. In the HOV lane the vehicle you are behind is pot luck and you tend to be behind them for 20 miles. Whereas on the longer route, I can pick and choose the vehicle I am behind.