What did I do wrong?

40 is lower than I have ever gotten for a tank, I would check tire pressure. I am not sure what my mpg would be at 75 and if there was a headwind. at 55 mph I get high 50s mpg and at 65 mph low 50s mpg. temp could have something to do with it. the underside of the c engine is not enclosed like the reg. prius. and with cold temps the heater will take engine heat. but at 75mph the engine will be making all the heat you could need for that. If you stop and take a nap and leave the heater run this could reduce the mpg a lot. I also notice a loss in mpg with rain. so if the roads are very wet or slushy you will likely have a drop in mpg.

 

Exactly right.

Wet roads cause a major hit to MPG. All that spray kicked up by the wheels is muscle that comes out of your fuel.

 

IMHO, the temperature and your speed kept the mileage down. And CC is of questionable use in maximizing MPG, unless it is used solely on completely level roads. Even small rises in the terrain cause unnecessary gas use when CC is on. Your own driving techniques, using the ECO score display as a guide, can usually do better.

If you expect to do 50 mpg or better on the highway in a Prius C, keep your speed under 70. Take full advantage of the terrain by letting the car gain as much speed as possible on down hills and drop back a few mph on uphill stretches, even slight ones.

But the biggest MPG thief, all other factors being equal, is cold weather. Don't be surprised to see it drop by 7-10 mpg. Hybrids only get good mileage because they allow the gas engine to be off for periods of time. When it's cold, you need the gas engine on more often just to keep the cabin warm. So your mileage will vary based on how warm you like to be.

Someone else said to just drive the car the way you would any other car. That's fine, if you really don't care about gas mileage. But you bought a Prius because you do. And the car has gauges that teach you how to maximize mileage by showing you in a dramatic digital fashion how each little movement of your foot on the gas pedal effects it. Pay attention to the ECO Score display, and take the time to browse this forum for other MPG tips. I am getting 60 mpg on my daily 40 mile commute, which is half highway. But I didn't get this until I learned how to drive the car for maximum efficiency, and it was definitely a change from my old way of driving.

 

Very true for short trips, but cold is not much of a factor on long trips if the roads are dry.

 

I don't know. I was getting an average around 50 or less in my daily 25 mile commute in the winter (mostly single-lane, very hilly, winding roads). Now that the air temps have warmed up this spring, I've been getting 60 mpg on average for the same trip and same driving style. Of course, I've turned the heat off now and I rarely use the AC. One very warm day, I decided to make the commute home with the AC on and my average dropped by around 8 mpg. Not a scientific test since I just did it once and traffic conditions may have been different. But at least in that respect, in my experience, air temps make a difference if you plan to use the heater or AC.

 

I wasn't thinking about cabin heating -- right you are, particularly if the cabin heating never lets the ICE warm up.

My habit of driving 5 - 10 minutes before I turn on cabin heating is so ingrained, I forgot that some people behave differently. And now that you have me thinking of accessory use that sometimes is turned on in cold weather, I'm reminded of the biggest leach of them all: defrost

 

worst I ever got on the HWY was 35 degrees, driving rain at 70+ mpg. I got between 45.5 and 46 mpg on a 477 mile trip going between 70 and 80 (averaged about 73 mpg) and it was 83 degrees outside. I get 56-58 mpg going 60 mph on the hwy. I found that 68 mph might be the magic number for high speeds. Exceed that number and mpg drops off rapidly, about 1 mpg per 1 mph increase after 60 mph roughly. by 80 mph I think 41-45 mpg is expected. So stay below 68 mph and 60 if u can. I get mid to high 50s or low 60s around town. It also helps im in the south and its warmer. On mornings when it was 29 degrees out Id get as bad at 38 mpg on my 6 mile city commute, but now that its 65 in the morning I easily get 58 mpg.

 

I made a 250 mile trip last weekend. I cruised at 70-75 and got 43 mpg average there and back. It was a little windy on the way down but not so much on the way back.

If your car is new-ish, I would expect lesser mpgs. If your car was full of stuff, I would also expect lesser mpgs. Cold out, and the same. Headwind, not using cruise, and a lot of hills, also lesser mpgs.

 

I don't think you have experienced enough foul conditions yet.

Just four days ago, crossing Eastern Washington into very strong head and crosswinds (plenty of dust being blown off agricultural field even without active machinery, and several sand dunes migrating onto the road shoulder) in otherwise great conditions (warm, dry, sunny), I saw just barely over 35 mpg at 60 mph for a two hour stretch.

 

Is it possible you are what they call a "2 footed driver", wherein you drive with one foot on the brake and one foot on the gas? I've seen people do this and get terrible gas mileage as a result, because they end up braking and accelerating at the same time, as well as having to replace the brakes frequently. Maybe I'm way off base, but just an idea. I drive my 2006 Gen 2 Prius at high speeds (75-80) on long drives, on not-so-flat roads and get 45+ mpg. Shorter drives my mileage is more like 40-41. Temperature doesn't seem to really be an issue.

 

CC at 75 mph will net you less than highway mpg rating. Throw in hills and lower temps and it get's worse. I can barely get 40 mpg on a long trip if I use CC at 70 - 75, have hills, and winds to deal with. Bentg stated he's not going to change his driving style so he'll get what he gets. But's it still better than most other vehicle choices.

 

Since it was 35 degrees this morning, compared to 70 the past two mornings, I figured it was an ideal time to try an experiment on my commute to work. I figured I could stand being in the car for 40 minutes without heat, so I left it off. Monday and Tuesday of this week (the 70 degree days) I got between 60 and 62 mpg on my 25 mile commute (no AC, no fan). This morning (Wednesday), it was 50 mpg. Driving style the same, road the same, traffic conditions very similar. The largest variable here was the outside air temp and it made a big difference. The interesting thing to me is that over the past winter, I was getting very similar mileage in the cold weather - around 50 on average but the thing was, I had the heater on at 73 all the time. So it seems to me that having the heater on doesn't actually cause as big a hit (if any) as I might have believed before. Perhaps that mpg deficit in cold weather at the beginning of the trip is just too great to overcome over a 25 mile commute. But I can say that for me, I won't mind turning the heater on next winter as I drive to work!

 

Right.

As for comfort, I compromise by leaving the cabin heat off for the first 10 minutes of the drive, to give the ICE and Cat a chance to warm up.

 

"The problem with this is that I can't drive it as I would any other car because it's much wimpier than most any other car. I knew that would be the case going in, but my way of thinking was the tradeoff would be awesome gas mileage. If I'm not even breaking 40mpg on a long, flat trip where nothing else changes from my typical driving except that my speed is increased, consider me sad."

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How was supposed to read that? You were expecting better mileage without changing your driving style.

 

Sorry if I mis-interpreted. Your last sentence threw me off; "...nothing else changes from my typical driving except that my speed is increased....". I took that to mean you didn't make any changes to your driving style except you drove faster. For you get better mileage, you will have to make adjustments to your driving style. BTW, simple changes will yield better mpg's in any car you drive, hybrid or not. There is plenty of tips in various PC threads, and even a youtube video that demonstrates how. It's an adjustment for sure, but I find you really don't have compromise as much you think you would, and certainly don't have to hold up traffic. On long highway trips, the only thing I do is keep my speed down - I don't need to do 80 mph when 65-70 will do, but I almost never do less than the speed limit unless traffic warrants it. During my daily commute with speed limits between 35 and 55 mph, I'm always in the fast lane and never go over 10 mph over the limit, and I'm averaging 44 mpg lifetime on my Prius v with 20k miles. Everyone's commute is different and you have to find what works best for you.

 

No worries!

 

Ya know, bentG,

For someone for loves his Prius and has a great attitude, you sure are causing a lot of commotion around here.