Good points.

Different cars certainly are affected differently by aggressive or high-speed driving.
And a hybrid-for-economy (rather than hybrid-for-extra-performance, like the Honda Accord Hybrid), maybe by its very nature, appears over-sensitive.
This should be realized by John Q. Public, but I can see how the message is not being sent. It's certainly not being emphasized anywhere.

We just see those glowing 50 MPG figures and think "I know I drive agressively, but I get near the EPA average, so I should get near this car's EPA average." And it doesn't quite work that way with hybrids. Thanks for pointing that out.
In addition: as an example, 85% of EPA on a EPA-rated 20 MPG auto is 17 MPG.
85% of EPA for the Civic Hybrid (50 EPA) is 42.5 MPG.
This simple truth just compounds the hybrid-not-getting-MPG-as-advertised complaints. If I was getting 17 on my EPA-rated 20 MPG auto, I think "45 or more is about equivalent on the Civic Hybrid", when in fact 42.5 MPG is equivalent.

The points I was feebly trying to make:
(1) If you didn't get near EPA with the former car, certainly don't expect EPA (and maybe not even near it!) on the Civic Hybrid.
(2) If you drive autos like they are race cars (ain't it fun, though ), don't expect good (near EPA) MPG. You're lucky if you get near it.

Another thing this points out are the inconsistencies about the EPA MPG testing procedures. I guarantee you that many autos would not give you the EPA-rated MPG with agressive and high-speed driving. My Jaguar and Benz are two that I own today, where MPG is KILLED by aggressive driving. I know I can take the Benz MPG from 15 down to 11 without much effort. Maybe the Jetta was slighted by the EPA, and should have a better EPA rating. Driving it very agressively, and being able to get almost EPA-rated MPG, while my Benz is clobbered by driving moderately agressively, shows something is out-of-whack. Maybe the EPA should be touted as "the best MPG the average conservative driver is likely to get - and ALL other bets are off".

None of this misunderstanding is the Hybrid's fault - although it is taking the blame. There's the shame of it all...

 

Actually the key with EPA mileage is to remember 3 things:

1) EPA tests in a lab on a dyno
2) Highway and City tests are done on a dyno (highway at 48MPH consistently I believe, and manufacturers often engineer their cars to perform well at that speed for EPA mileage sake and according to the "schedule)
3) If you read your window sticker, it says very clearly, City MPG should range from 41-57 MPG and Highway should range from 43-59.

For more on how the EPA tests:

http://www.fueleconomy.gov/feg/how_tested.shtml

If you leadfoot it and brake a lot, your numbers, no matter if in the city or on the highway, will drop radically...on any car...smooth acceleration and deceleration are always your friend...

As you can see from the stats users provide, many people acheive over 57 and 59 and many come in under.

Michael

 

Yeah the VWs are odd. The TDIs are rated at 34/42 IIRC yet TDI drivers regularly post how they get 50 mpg at high speed highway cruising... very weird.

 

The reason the Hybrids don't do as well relative to EPA is due to the nature of how they improve efficiency to begin with -- by scaling down an engine and using electric motors to supplement acceleration performance. The problem with this though comes in when it's necessary to generate a high, continuous load, where the batteries offer no help. This forces the smaller engine to wind out to a more inefficient RPM in order to produce enough power to cruise on the highway with accessories running, or climb a tall mountain at 60mph, etc.

This fact that allows hybrids to pull off amazing mileage for steady driving at 50mph makes them incredibly sensitive to additional load, whereas other cars with oversized engines actually move into more efficient powerbands on the freeway. This is offset by drag, but still leads to less of a relative drop-off compared to EPA than you'd see in a hybrid.

The problem with the EPA test is that if the auto manufacturers engineered a hybrid that would get better mileage in average highway driving, they would get no advertising benefit -- the unrealistic EPA driving cycle test number would either not change or even slightly drop, despite producing the same or better observed mileage for most people.

The EPA highway test should average at least 65mph, preferably 70mph or so, with occasonal bursts of up to 80mph for passing. There are many interstate highways now with speed limits of 75mph, and most with 65mph limits are enforced as if they were 75mph limits. This would better reflect the true observed mileage of a lot of vehicles, especially non aerodynamic ones like the Scion xB that manage to get excellent EPA highway numbers thanks to the low speeds. If hypermilers could improve on that by driving slower, nobody would complain, but I'm sure a lot less people woudl be disappointed about falling short of advertised marks.

The city test as it is inflates hybrid values for two reasons:

1) Lots of idling time -- moreso than seen in real life, tends to deflate non-hybrid values that can't shut the engine off.

2) Too short, so battery use is unaccounted for -- hybrids get to start off with a full pack, depelte it, and finish before it's necessary to replenish it. Running a longer test, or multiple trials of the same test without replenishing the battery in between would reduce error.

I'm not sure about the speeds in that test either, but there's a lot of ambiguity there. Does "city" mean somewhere New York City, which is almost nothing but idling, and has lots of stops, or Southern California suburban driving, where streets have 45-65mph speed limits and longer stretches between stops?

 

The city loop is a simulation of driving through downtown LA. The highway loop is a simulation of driving on suburban roads (not interstate) around Ann Arbor, MI.

Apparently the upcoming changes involve also factoring in a city loop where the temperature is below freezing, a highway loop at higher speeds and with quicker acceleration, and a highway loop at 80+ degrees with the A/C on full blast.

 

I'm getting close to 40 mpg around town, even with A/C on half the time (here in NC it's already "summer"), and about 45 on the highway, again with A/C on half the time. I average about 75 mph on the highway. I can lower the fuel economy significantly if I floor it all the time from stop. I don't drive like a granny, however, and still get decent mileage.

Aneil

 

Excellent post, Double-Trinity!

It's amazing the number of people that "want to believe" the EPA numbers more so on a hybrid (for some reason) when they know full-well they don't apply to their old vehicle.

The smaller engine working harder to keep up at higher MPH vs. the larger engine is definately true. My Jag gets BETTER MPG at 65 MPH than at 40MPH (it has an instant digital MPG gauge function on it).

I've often thought the EPA city-trip over-estimates the MPG of hybrids due to no consideration of returning the hybrid-battery to its initial state. They are essentially "reaping the reward" without having to "sow the seed."

The EPA testing procedures currently have the manufacturers "teaching to the test" rather than truly improving average MPG. The CAFE standards dictate it must be so. They typically do not care about real-world MPG, as that is not the standard they must meet.

Hopefully, with the revised EPA procedures, the numbers will become more realistic for the average driver.

 

In all of this, I'm seeing folks commenting on just driving style. There are two other things that people with significantly lower mpg also need to think about: topology and weather. My daily 35mi round-trip commute is generally pretty level (Ohio farmland), and there are only two traffic lights plus one stop sign I typically get held by, so I don't get a lot of opportunity to recharge the battery pack. The only thing I'm doing to get my higher mpg is keeping my speed down (53mph on one section, 48mph on the other), and coasting into those stoplights. The other thing I've seen that makes a difference is the weather. We're just now coming out of nearly two weeks worth of rain, and while before my mpg was creeping upwards towards 52, this entire tank has been a struggle just to keep 49 and my batteries from going into forced charge. I *think* I'll break 50 by the time I fill up again, but it's going to be a challenge since I've only got two or three commutes left to do it.

My driving style? Get to speed without flooring it or giving hybrids a bad name (2250rpm seems to push me just a little further ahead than the V8-driving granny next to me, but doesn't drop below about 25mpg on the instant gauge), setting the cruise, and forgetting about it for the ten minutes between stoplight one and the stop sign, then another ten minutes between the stop sign and stoplight two.