Any vehicles stand out as being exceptionally efficient at higher speeds?

[jamesqf]

Originally Posted by Ladogaboy

Anyway, in my opinion, you'll want to first assess how much time you're actually going to save by going 10 to 20 mph faster.

My impression was that he's less concerned about time, than about getting rear-ended by the other traffic on the road.

[johnunit]

I think some clarification is required:



Are we trying to find a car that gets better mileage at 75-85MPH than at 55, or a car that gets better mileage at 75-85MPH compared to the average car?


A new corvette or other sportscar (maybe the Lambo mentioned earlier) would likely qualify for the former, while a Prius, Insight, TDI VW, etc. would qualify for the latter.


I think the aerodynamics+engine load+gearing are what would would make differences in relatively comparable cars.

For instance:

the BIG elbow in my boat of a summer car (85 Crown Victoria, dead flat front end, 5.8L engine, 4200lbs, etc.) is at around 70MPH. I lose maybe 10-15% efficiency driving 65MPH instead of 50, but I lose 20% or more driving 75-80 as opposed to 65. 70MPH is about as fast as I can justify driving unless I'm in an emergency and it's long-distance.

However, this is with a 2.73 rear gear. That means that in OD 65MPH is around 1500rpm. Idling practically. With the 3.55 axle ratio that is a popular performance/acceleration choice in these cars, the elbow is at more like 60MPH because of the higher RPMs and the increased pumping losses from needing less throttle in OD to maintain a given speed. Go to a 1992-97 model of the same vehicle, basically the same trans but an engine with a higher designed RPM range and a much more aerodynamic body, and the elbow is at 70mph-ish even with the 3.55 axle ratio.

[BurningDinosaurBones]

Originally Posted by johnunit

I think some clarification is required:



Are we trying to find a car that gets better mileage at 75-85MPH than at 55, or a car that gets better mileage at 75-85MPH compared to the average car?

The thought here is to find out which car would be most economical , without advanced hypermiling, for someone who has no choice but to be on a fast busy highway for 90% of their vehicles driving life.

[BurningDinosaurBones]

Originally Posted by Ladogaboy

Sometimes, I'm just forced to ask why? Is it really so bad where you are?

That being said, I don't want to impose my values on you. However, physics isn't so kind. No matter what, you are going to pay a penalty for wanting to go faster. I'd say, given that the variables also include time, you should assess how much time would be saved by 55 mph versus 65 mph versus 75 mph etc. You said 5 hours, but that doesn't give us a good idea of distance. Are you saying roughly 300 miles? More? Less?

Anyway, in my opinion, you'll want to first assess how much time you're actually going to save by going 10 to 20 mph faster.

I agree with you 100%. In my normal life I don't go anywhere near the highway because it is a waste of fuel. I stick to secondary roads.

The place I'm moving to for work forces me into driving the way I've learned not to. The stretch of road in question has been said to be one of the most dangerous in the country, due to drugs and alcohol and excessive speed. I don't know if I'm going to believe the stories I've heard or not, but I'll find out when I get there.

I've got no issues with time, I just don't want to be a speed bump .

In reality I will probably figure out what the slack times are, and travel when traffic is at it's minimum so that I can drive properly .

[BurningDinosaurBones]

Originally Posted by serialk11r

Okay just ran some numbers with my Lamborghini example...
The Aventador has 7L, and spins at 2860rpm at 60mph. A Toyota Celica GT-S had about the same rpm for 60mph, but with 1.8L. This means we're asking the mighty 7L engine for only 1/3 of the torque that we're asking of the 1.8L engine, which is IIRC less than 25% of its available torque. The Aventador then is running at <10% peak BMEP...I think it's possible that 70mph could be better than 60mph in this car, despite the higher power requirement, because the engine efficiency is so much higher.

I don't know why people ignored my example, because the OP did ask for cars that got their best mpg at higher speeds.

Sorry I took so long to reply to this. I appreciate your response here, but my idea was to pinpoint the most economical highway commuter. The Aventador you speak of would most likely achieve it's peak economy at higher speeds than a normal vehicle, but may not be a cost effective commuter for me.

[mans]

U need 2 things

A low cd (or cda)
A low top gear ratio

One sedan sold in the us stands out above all others
It's the 2011 and 2012 Hyundai elantra.
.28 cd and 6 gear manual trams with excellent top gear (like .603)

I don't know of any other sedan in the US with such drag coefficient and gear ratio #'s

[serialk11r]

Originally Posted by BurningDinosaurBones

The thought here is to find out which car would be most economical , without advanced hypermiling, for someone who has no choice but to be on a fast busy highway for 90% of their vehicles driving life.

Heh, but that's not exactly what the OP said...it's what people are inferring! :O

But yea for practical purposes good aero cars...for cars that actually see an efficiency peak at high speed, high displacement bad gearing cars.

[IsaacCarlson]

A big motor in a small, aerodynamic car with good gearing will get better mileage than a small motor in a small car running at high rpm.

I am in the process of swapping a 3800 into a sunfire. I have to get a different differential and drive chain/sprockets to get the gearing low enough, but I am hoping to get 40 mpg. It is an easy car to mod and weighs 2600 lbs.

If you can get your paws on a used corvette and get a better final drive, you would do well, since corvettes normally get 30-40 mpg when driven lightly.

[redpoint5]

Originally Posted by serialk11r

Heh, but that's not exactly what the OP said...it's what people are inferring! :O

That IS the OP, and I don't think the question is ambiguous, despite the strange replies to this thread.

Originally Posted by BurningDinosaurBones

I wonder which vehicles can get the best fuel economy numbers at steady state higher speeds, like 70-100mph?

[cfg83]

BurningDinosaurBones -

Originally Posted by BurningDinosaurBones

Just a random thought today. I wonder which vehicles can get the best fuel economy numbers at steady state higher speeds, like 70-100mph? I remember reading about aerocivic's car getting ridiculously great mpg figures at high speeds, but what about the avg commuter cars?

What about VW TDIs? I would suspect they would perform well. My old 1993 burner certainly would not, it revs at 2800rpm at 60mph and only gets about 32mpg at that steady state speed...

Here is an interesting chart I like to use :

Green Car Congress: Fuel Consumption at Higher Speeds



All of them go down, but for some reason, in this test, the Mercedes C180K had a much gentler slope. On the other hand, it also starts near the bottom of the pack. I was thinking this was the aero-benz, but 2006 is not the right year.

CarloSW2