MPG at Highway Speeds (65+)

I was doing the same trip (Sacramento to Los Angeles) but while on I-5 I was driving at about 80-85MPH and got around 30MPG, stock Yokohama tires, 36-38PSI, same outside temperatures (cold). That also meant that the heater was on. I will admit that when driving that fast, it is difficult to constantly be on cruise control due to trucks on the freeway so MPG will go down a little.

Going up the Grapevine is a real killer, but kinda evens out when you go down the other side.

Mike

 

I like the graph(thanks) and I noticed sweet spots their at 50mph and 60mph so while driving I use that on peaks and valleys

 

Wow, I did not know you can get it that low!

With those numbers, I doubt a 4cyl Camry with the 2.5 would do much worse.

 

I am really jealous of you guys that live in the good weather all year around. Today I went 610 miles and averaged 46.6 mpg on the display, which about 44 actual. The last tank is about half empty and it's showing 49.7 mpg. I have the tires pumped up to 45 rear and 43 front. Temp at the start was 28F on the first tank and ranged 28-42F. The second tank temp ranged from 28-42F going over the Siskiyou Pass, and up to 54 through Redding Ca. I had the cruise set at 73 indicated ( 71mph by the Garmin ). The 20 mph tail wind didn't hurt either. Good temperatures and dry roads really make a difference.

 

I didn't think it would get that low either, but I was driving pretty fast. I'm sure the temperature being low and my heater having to keep me warm didn't help much. But I think the graph that somebody posted, if it went as high as I was driving, would show about the same MPG as I was getting.

I think you are right that such a Camry or Corolla wouldn't do much worse. But I think the issue is that if I wanted better MPG, I just needed to slow down. I think the same is true for the Camry or Corolla, but the benefits wouldn't be as great. At least we have that option.

I will admit that my thought was not to worry about MPG but to get me home ASAP.

Mike

 

Even with temps in the 40's dry roads make a 5 mpg plus difference
compared to rain and wet roads.

When I use the ac on those 3-4 days here in the northwest every
year, yes there is no r e a l summer here, I notice no decrease in mpg compared to the winter when I have to use heat, lights, windshield wipers etc.

alfon

 

I think you're going to like spring and fall but you're going to take a hit in summer when the A/C will be working at full tilt.

To give you some idea, on two 320 mile round trips, mostly 65mph Interstate, plus sections of 50mph and 55mph, temperatures in the 70s, 5 people in the car (4 adults +skinny teen or 3 adults and 2 teens), A/C running on LO we got 52-53mpg. Note that that's on the rolling hills of ME and NH Interstates and the tires are above placard, probably 39/37.

So you'll get better as a lone commuter, will get better if you're on flatter roads, but will take a hit from any higher speeds and the A/C in the summer heat.

 

Here on the Oregon coast we don't have a summer. We haven't used an air conditioner here ever here. We will use it when we travel.

My wife doesn't really care about mpg's as long as it's above 40, so when she is with me, we usually drive as fast as we can and not get caught. Yesterday we drove mostly 75+, we just barely made her 40mpg limit.

 

At that exact speed, on a 200 mile highway trip ... I regularly get 57 MPG.


REV

 

Out of curiosity which tires are you running?

 

On a recent ~400 mile trip on the interstate. 2 adults and 2 children. Light baggage. Temps about 55 degrees and speed about 75 mph. Prius showed 46.2 mpg and calculated was 43.2 mpg.

 

FWIW... I rented a 2011 for a recent trip to make sure that my 6'3" frame would ride in it well (which it did). Prius showed 48.5 after 500 miles. 300 miles of that was at 70 - 72 MPH, 150 miles of that was at 50 - 62MPG. Temperature ranged from 22 (first 200 miles) - 65 degrees. Didn't figure out the calculated as I just needed to return the tank 50% full.

2 adults, 2 kids and a trunk full of stuff.

 

Have no idea about the fuel usage in the power mode, But i did get her up to 97 climbing a hill, I said to my wife, Wow this thing has some power. lol :rockon:

 

I kept my speed within the range between 55-80mph, probably averaging 65mph, and my mileage was 65mpg.

 

Over the course of a full tank or just what you saw on a specific trip?

 

The Prius is a fine car, but let's not get carried away here, ok?

 

Last night I had to take a little highway trip to pick up some family members & I didn't worry about mileage, but about time. My mpg suffered more than I would have guessed.

Previously, I had easily been able to get 60+ on highway trips, but last night, driving at 70-80 (mostly around 75), combined with rain and later 2 passengers, luggage, and a dog, I fell down to about 48mpg for my highway portion. I was extremely disappointed.

(Isn't that funny? Last month I was driving a truck that got 18mpg on the highway, and now I'm disappointed that I dipped below 50. haha!)

The moral of the story is that 60-65 really seems to be the "sweet spot" for highway mpg, and when you go faster, it's like falling off the edge of the mileage cliff.

 

Bob Wilson's work, posted as a graph in #12 earlier, would suggest that such a 'sweet spot' is actually a myth. Unless of course we are talking about the slight 'hump' on that down curve.

If such a 'hump' exists it might be elusive because it is different for every car because of differences in specifications, driving environment, etc.

For the guru's out there, what would you think are the best strategies for an individual to find his/her own 'sweet spot' for highway driving?