The 40-MPG Challenge

[50 mpg by 2012]

The 40-MPG Challenge

Six Cars Claim To Get 40 MPG, but Do They Really?
Published: 06/14/2012 - by James Riswick, Automotive Editor

Forty mpg. It's a number you've probably heard on TV commercials or seen on billboards. After all, just five years ago, there were only three cars that could make this lofty claim for fuel efficiency on the open road, and two of them were hybrids and the other was the Smart car. Fast-forward to 2012 and there are now 24 models that claim to get EPA fuel economy of 40 mpg highway, and 15 of them aren't even hybrids.

We gathered six of these cars that the EPA says get precisely 40 mpg on the highway — none of them hybrids — and tested them in the real world. Is it really possible to achieve that big four-oh? Will each car really return exactly 40 mpg on the highway, as the EPA numbers indicate? And how will they do away from the highway in the sort of suburban environment in which most Americans drive every day?

This is the 40 MPG Challenge. Six cars, 700 miles and your choice of energy drinks from the gas mart.

It is a relatively long and detailed article so ...

http://www.edmunds.com/fuel-economy/the-40-mpg-challenge.html

 

[Throckmorton]

Yep, the stricter CAFE requirements are working.

5 years ago turbos were rare, now it seems like every car has an optional small turbocharged engine.

 

[foghorn67]

Yep, the stricter CAFE requirements are working.

5 years ago turbos were rare, now it seems like every car has an optional small turbocharged engine.

I think DI helped a bit.

 

[Doppel]

However, for the great many who live in less populated metropolitan areas and do much of their driving in the suburbs, our test results collected from 180 miles of driving around the greater Las Vegas area should be fairly representative of real-world mpg.

This isn't city; it would be more considered combined, which is about the numbers the cars saw.

The Interstate Highway Route

Now that is interesting. The TDI definitely surprised me with its finding. And the other cars did, too--about how bad they were. Those are terri-bad numbers from the bottom three. A lot of people with a lot of cars find that they can match EPA, sometimes beat it, even at highway speeds.

 

[ElFenix]

ya i easily beat EPA at highway speeds, even going 80+ for long stretches. don't know why the magazines always have problems achieving that.

 

[IGemini]

ya i easily beat EPA at highway speeds, even going 80+ for long stretches. don't know why the magazines always have problems achieving that.

Magazines likely don't drive at above-limit flow-of-traffic highway speeds, and a little-known secret is that many cars are actually more efficient at those above-limit speeds. The only times I've exceeded EPA highway MPG numbers for my car was when I was able to stay ~80 MPH on the highway for a decent amount of time. Similar principle to CPUs being more efficient by getting work done faster.

I'm not sure how applicable it is to compact cars since they have less-powerful engines...they might even lose efficiency at those speeds but I haven't tried.

 

[Ketchup]

For one thing, car magazines get cars when they are still pretty 'green.' IT takes a couple thousand miles of breaking in before the engines return their best mileage and performance.

Having said that, I have been a subscriber to C/D for years, and I think they have a lead foot anyway.

 

[nerp]

Magazines likely don't drive at above-limit flow-of-traffic highway speeds, and a little-known secret is that many cars are actually more efficient at those above-limit speeds. The only times I've exceeded EPA highway MPG numbers for my car was when I was able to stay ~80 MPH on the highway for a decent amount of time. Similar principle to CPUs being more efficient by getting work done faster.

I'm not sure how applicable it is to compact cars since they have less-powerful engines...they might even lose efficiency at those speeds but I haven't tried.

Very applicable. My Yaris fell off a cliff above 65mpg. My charger gets 33-34 at 80mph where my Yaris would have started falling below 30 at that speed. A lot of it has to do with transmission. Fifth gear in the yaris going almost 3200rpm vs. 1500 rpm @ 80mph in 8th gear in the Charger.

 

[skyking]

for those that claim higher MPG at high speeds, I have one question.
Is this assumption made from an instant display, or from driving a tank out @75 MPH, filling it, and doing the math?

 

[IGemini]

for those that claim higher MPG at high speeds, I have one question.
Is this assumption made from an instant display, or from driving a tank out @75 MPH, filling it, and doing the math?

In my case, the latter. My car has no instant MPG readout, just a trip & total odometer. 2000 3.8L Impala, best I ever got was 28.5 MPG. EPA numbers here

EDIT: My family did have a 3.4L of the same year, I muscled 34 MPG out of that.

 

[Doppel]

http://fueleconomy.gov/feg/driveHabits.shtml

 

[skyking]

did you ever do the same @ 60 MPH?

 

[50 mpg by 2012]

for those that claim higher MPG at high speeds, I have one question.
Is this assumption made from an instant display, or from driving a tank out @75 MPH, filling it, and doing the math?

No display, Interstate @ 65~80 mph no A/C, over 450 mile each way

Personal Experience: Calculated slightly above 32 mpg highway both times. Around town 24 mpg until odometer reach 224k ... now about 22.5 mpg city at 226k.

1995 Honda Odyssey 2.2 L, 4 cyl, Automatic 4-spd, Regular Gasoline

18 City 20 Combined 22 Highway 24.8 user average Show Details


1995 Honda Civic 1.5 L, 4 cyl, Manual 5-spd, Regular Gasoline [2dr HB]

35 City 38 Combined 41 Highway 36.4 user average

No display, state highway @ 55~65 mph with A/C, over 300 miles round trip (150 mile each way) two or more times/month

Personal Experience: 45 mpg highway ... and 38 mpg city

Both odometers have been checked against Interstate mile markers, appear to be within 2%.

I hope this helps.

 

[50 mpg by 2012]

This isn't city; it would be more considered combined, which is about the numbers the cars saw.Now that is interesting. The TDI definitely surprised me with its finding. And the other cars did, too--about how bad they were. Those are terri-bad numbers from the bottom three. A lot of people with a lot of cars find that they can match EPA, sometimes beat it, even at highway speeds.

Fuel frugal small displacement Euro type turbo diesels USER MPG Estimates usually exceed EPA mpg combined by 23%.

See Audi/VW at http://www.fueleconomy.gov/mpg/MPG.do?action=browseList

There is a discussion about this in SAE Technical Papers #2011-01-0618 © 2011: "Predicting Individual Fuel Economy" by Lin, Z., and Greene, D. Oak Ridge National Laboratory

 

[skyking]

Doppel posted a link that says it all for me. Physics say you will get better economy if you slow down. It has been my experience as well.
I think people will try to justify their driving habits any way they can, with anecdotal evidence of higher MPG at higher speeds.

 

[Ronstang]

for those that claim higher MPG at high speeds, I have one question.
Is this assumption made from an instant display, or from driving a tank out @75 MPH, filling it, and doing the math?

I have ALWAYS calculated gas mileage from actual usage numbers. I usually use a long trip as my benchmark for highway mileage where I am basically going a set speed on the highway for an entire tank of gas. You can't factor in things like wind and changing grades but if you do it enough you get a fairly representative average.

I have found some interesting things doing this over the 33 years I have been driving.

1. I have always beaten EPA ratings.

2. At least on older cars, last tested a 1993 Taurus SHO best mileage was with the windows down and the AC off.

3. Gas mileage is heavily dependent on gearing and where you are in your torque curve. It can be more important than speed. Even considering wind resistance higher speeds can yield the best results especially on cars with overdrive. Sometimes the overdrive is simply too much and lowers the engine RPM below an efficient level.

My 1985 Mustang GT had this problem. At 55 mph on the highway I would get 25 mpg, yet at 70 mph I would get 27 mpg consistently tank after tank of comparison. This was because the final drive ratio was simply too high to keep the engine in an RPM range where efficiency was maximized. My Taurus SHO also got better mileage at 70 and even better than the EPA rating.

 

[Ronstang]

Doppel posted a link that says it all for me. Physics say you will get better economy if you slow down. It has been my experience as well.
I think people will try to justify their driving habits any way they can, with anecdotal evidence of higher MPG at higher speeds.

You need to stop looking at things that are generated based on theory and not testing. My experiences have proven this to be false many many times. It is vehicle dependent but you do not necessarily get better mileage at lower speeds.

Plus, it is a government generated graph so it is much more likely to be skewed to try and influence behavior the way the government feels something should be.

 

[Ferzerp]

I lose about 20% of my mpg between 60 and 80, but I stll get twice the mpg at 80 that I get in stop and go city driving

 

[skyking]

I concede that gearing issues and inefficient gas engines will sometimes belie the physics of the aerodynamics.
I do plenty of testing and it lines up with the physics more often than not.

 

[Ronstang]

I concede that gearing issues and inefficient gas engines will sometimes belie the physics of the aerodynamics.
I do plenty of testing and it lines up with the physics more often than not.

That graph is probably more accurate if you only consider cars made in the last few years. Auto makers have figured out quite a bit in the last decade. They have been forced by extremely high gas prices to be more careful when choosing the gearing.

 

[IGemini]

Gas mileage is heavily dependent on gearing and where you are in your torque curve. It can be more important than speed. Even considering wind resistance higher speeds can yield the best results especially on cars with overdrive. Sometimes the overdrive is simply too much and lowers the engine RPM below an efficient level.

This.

I have a huge amount of experience driving 8th and 9th generation Impalas, and their power/torque curve is pretty interesting. The 8th gen 3.4L engine is pretty underrated in its efficiency, and even newer Impalas weren't as efficient for a while. It's rated for 20-29 but it wasn't uncommon for us to get 30-31 (90% highway driving around here). The 34 was attained under an interesting set of circumstances--600lbs worth of people in the car, some degree of slipstreaming, and speeds up to 85MPH on the highway. Better center of mass and wind dynamics? It's possible. Lots of things factor into mileage.

My driving habits have been pretty consistent since I started, and my basic philosophy has always been that of "reasonable haste." NY traffic flow accepts 0-10 over the speed limit (i.e. the police won't pull you over, I've lost track of how many speedtraps I went through), I follow the 2 second gap, and I avoid aggressive acceleration & braking. Don't use AC unless it's really f'in hot, 2 days a year maybe.

 

[Doppel]

You need to stop looking at things that are generated based on theory and not testing. My experiences have proven this to be false many many times. It is vehicle dependent but you do not necessarily get better mileage at lower speeds.

Plus, it is a government generated graph so it is much more likely to be skewed to try and influence behavior the way the government feels something should be.

http://www.mpgforspeed.com/

 

[skyking]

Interesting how flat the mercedes graph is. They do have some very good aerodynamic improvements over the last few years.

 

[superccs]

No display, Interstate @ 65~80 mph no A/C, over 450 mile each way

Personal Experience: Calculated slightly above 32 mpg highway both times. Around town 24 mpg until odometer reach 224k ... now about 22.5 mpg city at 226k.

1995 Honda Odyssey 2.2 L, 4 cyl, Automatic 4-spd, Regular Gasoline

18 City 20 Combined 22 Highway 24.8 user average Show Details


1995 Honda Civic 1.5 L, 4 cyl, Manual 5-spd, Regular Gasoline [2dr HB]

35 City 38 Combined 41 Highway 36.4 user average

No display, state highway @ 55~65 mph with A/C, over 300 miles round trip (150 mile each way) two or more times/month

Personal Experience: 45 mpg highway ... and 38 mpg city

Both odometers have been checked against Interstate mile markers, appear to be within 2%.

I hope this helps.

I cruised back from Salt Lake City in a 1990 CRX DX doing 90mph and made it to Las Vegas 450 miles later and used 10 gallons of 87. Too bad all new cars have to be so safe... I would rather have a CRX and wear a helmet then drive any new POS from Honda.

 

[NutBucket]

LOL! A helmet isn't going to do shit for you in a crash....unless you want to live in a jar like in Futurama.