Real World Highway MPG @ 75-85 MPH speeds?

I've averaged the C's 46MPG highway going 75mph+ once or twice, and that's only with the wind not working against me or working in my favor

At those speeds on the highway with the C, you might want to draft behind someone if you want good MPG and not be the leader of the pack

 

I guess you don't plan on keeping your car very long, this type of speeding will cause oil burning around 100k mile mark, as well built as this car is, hard driving equals short life. I know this has been debated, that RPM is not high at these speeds, but I have seen it happen to a friends car, which was maintained, but driven hard for 4 years, and now burns 1 quart every thousand miles.

 

I'm not planning on driving it that hard for ever. Just one more trip. Not really much of a speed demon any more. But I appreciate the words of advise. I'll be checking my oil more frequently. Thanks for the heads up.

 

I drove my 2001 Saturn very hard and I can guarantee to you that it didn't burn 1 qt every one thousand miles.... even with over 150k miles and a styrofoam engine.

 

I agree with you, since my C I became a different kind of driver

 

You are totally right !!

 

So did the drive, this time I didn't exceed 70 for longer then a minute or two. Maintained speeds around 65 for 80% of the trip and around 55 for the remainder. It added some time to the trip, around 30 minutes or so. Plus the temperature outside was between 33-39. It got colder as I was nearing Dallas. Car said I averaged 49.5MPG. I pulled into directly into a gas station .1 miles from the house and calculated real world MPG of 47.7. Not bad for being cold outside. The Prius C does pretty well in winter for long trips IF speed is maintained around 65. I did not set the cruise, just used normal driving, and took advantage of hills. No advanced techniques while driving, just maintained 65mph.

 

Regardless of the name, the C will cruise just fine at 70 - 80 mph on the highway. Or since "C" stands for "city" should we not be driving it on the highway at all? ;-)

SCH-I535 ?

 

Hard acceleration that revs the ICE will put engine wear on the C more than gently accellerating to 80mph.
The C has a continuously variable transmission and will always optimize overdrive ratios and keep ICE speed low if driven gently even if driven fast.

In fact maintaining 55mph up a hill and down the other side will put more wear than letting the car slow down on the way up and then accellerating to 80 on the way down.

SCH-I535 ?

 

Yeah... that's not realistic though in most situations... you know what else would be easier on the engine? Turning it off and letting the car behind you push you up the hill.

 

Yeah, I was just illustrating that the raw speed of the car is not the determining factor of ICE speed/wear.

SCH-I535 ?

 

The regular Prius is geared so gas engine revs lower due to higher torque from 1.8L engine. The engine also has wider range of sweet efficient spot.

See the BSFC where c should be similar to Gen2's 1.5L.

 

That's about right. The fastest you go the lower your MPG will be. I also agree with the statement of the Prius not being the right car if you are planning to commute at 80 MPH. I mean, you can do it but you will never see the efficiency of these cars.

 

In a driving rain storm 260 mile round trip and 32-37 degrees F, I got 41.8 mpg going about 70 mph most of the way. On a trip to/from the mnts about 240 mile round trip going 70-75 mph I got about 53 mpg but was dry and sunny and 55 degrees. If I travel locally for 20 miles or less at 60-70 mph I get 52-54 mpg. Im about to drive about 1000 miles to/from Florida doing 65-80 depending on speed limits and traffic, so cant wait to see what I get.

 

FWIW maybe the C isn't the best choice, but the standard Prius is still one of the most efficient vehicles you can drive at high speeds. And based on people's observations on this thread so far, even the C doesn't suck at all. All vehicles will take an mpg hit at these speeds. Its physics. The Prius with its low drag and high efficiency engine still does really well when driven at sustained high speeds.

This article does a good job of showing that effect on other contenders.

40 MPG Compact Sedan Comparison - Chevy Cruze Eco vs. Ford Focus SFE vs. Honda Civic HF vs. Hyundai Elantra GLS vs. Mazda3 vs. VW Jetta TDI - Motor Trend

At the bottom of the first page they provide a very handy graph of measured constant speed fuel consumption. Unfortunately it only goes up to 75mph, but here's the results at that speed:

Make/model : EPA Highway: Measured MPGs at 75mph constant
Hyundai Elantra: 40mpg : 35mpg
Ford Focus SFE: 40mpg: 35mpg
Mazda3: 40mpg: 36mpg
VW Jetta TDI: 42mpg : 38mpg
Honda Civic HF: 41mpg : 39mpg
Chevy Cruze Eco: 42mpg: 41mpg

Now compare that to Bob Wilson's data on the Prius:
Prius Liftback: 48mpg: 47mpg
Prius C: 46mpg : 42-45mpg?

Its also interesting to consider the above in the context of Consumer Reports estimated 8 year total ownership costs:

Make/Model: 8 Year TCO
Toyota Prius C: $34,750
Toyota Prius IV: $39,500
Honda Civic EX:$41,750
Mazda3: $43,250
VW Jetta TDI: $44,000
Hyundai Elantra: $46,500
Ford Focus: $47,500
Chevy Cruze LS: $47,500

Given those two pieces of information, I'd say the Prius / Prius C are still pretty compelling choices for the high speed / high mileage commuter.

Rob

 

This is not true. The reason cars burn oil is more to do with maintenance issues.

I have driven the hell out of too many Toyotas burning no oil after 150,000 miles to believe hard driving causes oil burning. Sure if you red line it often then maybe.

And actually, driving too easy especially on a new motor can cause it to burn oil.

 

just got back from a 1000 mile round trip to/from Florida. It was sunny and dry the entire trip. Did 70 mph with CC on the way and got about 47.5 mpg. Did about half 70 mpg and half 75 mpg on the way back and got 46.5 mpg. I found it drove ok on the hwy. I also did 60 mpg for 20 miles after a fill up just to compare and the computer read over 58 mpg. But the posted speed limit was 70 mph and even semis wanted to blow by me. Next trip Im going 80 mphs when I can like I normally would, time is too valuable to me

 

Speed and time become a huge factor especially at those distances. Any distance over 300 miles, I'd rather take the MPG hit and save time. On a 280 mile trip, driving at 75-80 vs 60-65 on the highway stretches, saves close to 35 minutes. You drove about 4 times that length, you can easily save 2 hr's worth of driving.

 

In the future, when a car can drive itself, can go at 50 or 60 mph while I sleep

 

and then it doesn't matter how long it'll take because you'll be well rested when you get there, lol.