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What will be the MPG when driving on the highway at 70 mph?

  • Less than 30 mpg

    Votes: 7 4.0%
  • 30 mpg - 35 mpg

    Votes: 29 16.8%
  • 36 mpg - 40 mpg

    Votes: 75 43.4%
  • 41 mpg - 45 mpg

    Votes: 42 24.3%
  • 46 mpg - 50 mpg

    Votes: 9 5.2%
  • More than 50 mpg

    Votes: 11 6.4%

Fix: What will be the MPG when driving on the highway at 70 mph?

41K views 71 replies 38 participants last post by  thetoad 
#1 ·
Don't just vote, stake your claim and post it. As the poll creator, I don't want to sway the poll so I'm going to post mine later (it's the same that I posted many times before).
 
#39 ·
"George, Thanks for that number. Can you give us the details of how this number was calculated? There are a few other Prius owners and if we can get a couple of people agreeing on this, we will have a good base of comparison.

1) Did you use real calculated numbers based on fill-ups or just use the Prius meter?

2) Did you do long runs at 70 mph or just short runs?

3) Did you run the test multiple times or just once?

Thanks!"--Texas

The numbers are based on the meter. It was on a long trip from Phx to Oregon. The easiest place to get a nice steady state number was on the freeway approaching Fresno, Ca. It is miles and miles of flat road. I made one attempt to verify the the meter using actual gallons and miles and got around 4% lower than the meter but I think the test would need to be repeated a bunch of times to really know for sure.
In my daily commutes I get a very consistent 52 MPG. However, thats for an average speed of more like 59MPH and it involves rolling hills and elevation changes. If there is energy to recover the Prius gets better mileage.
 
#43 ·
more good data

The following site has government test data on the EV1
http://avt.inel.gov/pdf/fsev/eva/genmot.pdf

The interesting data relevent to this question about gas mileage at 70 MPH is the following constant speed data for the EV1.

45MPH=115 w-hr/mi(8.7 mi/kw-hr)
60MPH=164 w-hr/mi (6.1 mi/kw-hr)

If you crossplot this data you come up with some interesting conclusions:
1) Laukners claim of 130 w-hr/mi (for the highway drive cycle, avg MPH=48) plots right on the EV1 data.----just as BillR observed in his thread on 150MPG EPA rating.

2) Extrapolating the data to 70 MPH the EV1 gets 190w-hr/mi (5.3 mi/kw-hr)--excellent electrical efficiency!!

Now if we say that the volt will equal the EV1 in electrical efficiency as Lauckner is stating then we need to convert this number into MPG thru the ICE/ series drive train. With the following rather liberal assumptions of 37% ICE efficiency and 92% efficiency for the generator/inverter/motor and 33.4 kw-hr/gal heating value for gasoline we get 60 MPG for the volt at 70MPH.

Therefore I stick by my prediction of 50 MPG or better for the volt.
 
#44 ·
The following site has government test data on the EV1
http://avt.inel.gov/pdf/fsev/eva/genmot.pdf

The interesting data relevent to this question about gas mileage at 70 MPH is the following constant speed data for the EV1.

45MPH=115 w-hr/mi(8.7 mi/kw-hr)
60MPH=164 w-hr/mi (6.1 mi/kw-hr)

If you crossplot this data you come up with some interesting conclusions:
1) Laukners claim of 130 w-hr/mi (for the highway drive cycle, avg MPH=48) plots right on the EV1 data.----just as BillR observed in his thread on 150MPG EPA rating.

2) Extrapolating the data to 70 MPH the EV1 gets 190w-hr/mi (5.3 mi/kw-hr)--excellent electrical efficiency!!

Now if we say that the volt will equal the EV1 in electrical efficiency as Lauckner is stating then we need to convert this number into MPG thru the ICE/ series drive train. With the following rather liberal assumptions of 37% ICE efficiency and 92% efficiency for the generator/inverter/motor and 33.4 kw-hr/gal heating value for gasoline we get 60 MPG for the volt at 70MPH.

Therefore I stick by my prediction of 50 MPG or better for the volt.
50MPG would be great even without the extra 40 miles you get. I hope you are right.
 
#47 ·
In my 7 cross country trips since I have owned the 2012 Volt, I typically drive at 65-70 in the east and 70-75 in the west. I typically average between 41 and 44 mpg for the total trip with a car chock full of stuff. I have seen it drop below 40MPG in Texas where the speed limit is sometimes 80mph.
 
#48 ·
I had a Cruze LTZ (turbo etc) rental for about 2 weeks. Beat the hell out of it, showed a neighbor and his $33,000 turbo Mini that he could not keep up ANYWHERE on Paris Mtn., averaged 30 mpg overall and on I-85 from Greenville to Gastonia at 60-65 mph the mpg was 43. The year the Volt arrived the factory Chevy guys at Auto-Fair said if you ran the Volt in G/E and did away with all the high tech (spell that HIGH DOLLAR) stuff, you could drop the price to the low 20's and average 35-45 depending upon your driving habits.

And why do they not do that? I'm betting on a plain gas/electric or diesel/electric just is not as cool or sexy.
 
#51 · (Edited)
My Volt at 65 mph is getting 42 mpg. At 70 mph I think it would be the same-ish. Surely over 40. This is why I voted 41-45 mpg.
It is better then my ex Ford Focus 2012 who at 65 mph made 39 mpg and at 70 mph made 36-35 mpg.

The image is from my last trip where I was on the highway 90% of the time at 65 mph, cruze control, and some speeding up to 80mph in short runs.
 

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#55 ·
I put it in hold mode just prior to taking the entrance ramp onto the freeway (with 10 miles left on the battery). 16 miles later after taking the exit ramp, I achieved right at 39 mpg. Flat terrain, 95 deg F, kept it between 70-75 mph, no drafting trucks. Only the weight of myself in the car.
 
#56 ·
I probably have more experience than most with this type of driving (>50,000 miles at ~70 mph on ICE). The Volt averages very close to 40 mpg (+/- 2 mpg depending on conditions) at 70 mph. I've gotten as bad as 36 mpg with a headwind, and once ~34 mpg after what I believe to have been a bad batch of gas.
 
#57 ·
2013 Volt
1,600 miles driven over Christmas from VA, down to Montgomery AL, and some running around there (all electric). Highway speeds were 70-75mph for the entire highway trip and I ran on "hold" mode. For a portion of the drive we were in heavy rains (and all the extra resistance that entails). MPG running on just the REX was 38.7 at the worst (rain) and 41.2 for most of the rest of the time. Tires were just slightly overinflated to 40 PSI. Two people and a passel of Christmas presents so about 400 lb cargo weight.
 
#59 ·
With or without a full charge at the start? If "with", then it's more like 40-44 MPG, because you need to lop off the electric miles to see the actual gasoline consumption rate. Which is still nice, but more in line with what everybody else is reporting.
 
#60 ·
I've had my 2017 since April and have put on 4000 total miles including 3000 highway and 1000 EV miles. My mileage is 55 mpg. The highway miles include two 1000 mile trips and a 500 mile trip. The 1000 mile trips were roundtrips over the .Pacheco Pass and the Tehachapi mountains; the 500 mile trip was a roundtrip over the Donner Summit. My driving style was moderatly agressive on these trips. My typical gas cost is about $2.50 p/g. My electricity cost to date is the equivalent of about $0.88 per gallon of gas. I couldn't be happier.
 
#63 ·
Over a long-distance on gasoline, the Volt is less efficient than the Prius. Gen I Volt will get approximately 41 MPG. The Prius will be able to get about 48 MPG. However, if the long-distance trip is blended with short-term plug-in commuting, then I would anticipate around 80 MPG with the Volt. Sweat equity is greater with the Volt.
 
#65 ·
Over the Memorial Day weekend, we took a 2-hour one-way trip that was about 86 miles on the Interstate. We achieved 46 MPG over 66 miles, going about 70 mph. Climate control was turned off. Elevation had some gentle hills (I-66 to I-81 south in VA). External temp was in the 60s.

 
#66 ·
Keeping your speed below 60 mph will place your 2016-17 Volt pretty close to 50 mpg on gas. My recent round trip with our 2016 Volt for 135 miles, 70 miles on electric, and 52.5 mpg on gas. This was a fishing trip to Tillamook Oregon via Highway 101, speeds 60 mph max and 45-25 mph through towns, dry roads and 60 degrees. The gas mpg on the Volt was about 3-5 mpg less than I would have obtained with our 2010 Prius under the same conditions and climate etc.
 
#67 ·
I drove my 2017 Volt from Denver to New Hampshire and back. Gas MPG was 38-39 MPG over the 4,000 miles. I tend to stay within 2 or 3 MPH of the posted speed limit on cross country drives. Colorado, Kansas, and Nebraska all have 75 MPH speed limits and the rest of the states were 70 MPH on the interstates. Primary, non-interstates ran the gauntlet from 25 to 65 MPH.
 
#68 ·
I make a 180-mile trip twice per week. At 70 mph my round trip average sits at about 35 mpg. At 65 it is close to 40 mpg. At 75 mph it drops to 32 mpg. This is with 90-100 degree temps, AC on ECO 72 deg.
 
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