Sounds like advertising industry best practices to me.

We bought a Prius six years ago so my wife could use the carpool lanes for an hour-long commute through Los Angeles. We didn't get the EPA's mileage, but it's still double the mileage of our other car.

Since the EPA does the testing and approves the mileage figures, doesn't this shield the manufacturers from liability for inflated numbers? The EPA sets the testing criteria. I know that I never hit the estimated city mileage for my conventional car and never expected to, so I only use the published gas mileage numbers to see relative mileage between cars. I never thought I'd hit that number exactly.

That said, the Prius owners I know are quite happy with their 40mpg+ mileage and are close or even over the published mileage. Granted, it takes a difference in driving style to hit that number (for example, by maximizing regenerative braking), but most people that buy a Prius are willing to help it maximize their mileage.

If you live in a city, one option to having 2 cars might be to join a city car share program. If you rarely need the range of a gas powered engine, it could be a cost effective alternative to owning two cars. Plus you can choose the car that best meets your needs - take a sporty convertible for a weekend getaway with your wife, take a minivan on the long trip with the kids, take a pickup truck to the hardware store, etc.

http://www.zipcar.com/ [zipcar.com]
http://www.citycarshare.org/ [citycarshare.org]

Which if you think about it is pretty pathetic. Diesel cars have been able to get that for years. There are definitely places like Minnesota where diesel is a lot less realistic, but hybrids aren't going to make much sense there either as batteries don't like the cold any more than diesel does.

The only way your GTI gets 31 mpg is if the stoplight in question is at the top of the mountain and you coast the rest of the way down. Sheesh! You're not going by what you see while cruising on the highway up on the trip computer, right? (BTW, 'trip computers' are notoriously bad from what I've seen. If you go to forums for a particular car and look at what the trip computer folks are reporting, vs. the people who really measure, you can often see a 5-10 mpg difference, with the trip computer almost always reading high.) GTI's typically run in the 16-22 mpg range, depending on how driven and type of driving from what I've seen.

You're correct however, about the TDIs. Our Jetta TDI has averaged 34.58 mpg over about the last 1.5 years in mostly city driving (measured by filling the tank at the same station and pump most of the time, and recording the amount of fuel and distance traveled each time... not quite as accurate as some methods, but much better than the trip computer.... and over that long of time, it starts to become pretty accurate.) We've never really taken a true highway trip. The closest we came is a trip through the mountains where we got 41 mpg for a tank. I know the TDIs are capable of much better in true highway situations.

There's certainly hype, possibly too much, but the devil is in the details here.

Gasoline-based internal combustion engines get a theoretical maximum 30% efficiency in converting the heat of burning the fuel into work. (This is the major reason why the conventional direct-drive internal-combustion engine configuration requires a radiator -- that lost 70% is being dumped out of the car as waste heat, minus the small fraction that's used to heat the interior of the car in the winter.) Non-hybrid configurations also have to size the engine for the maximum power output it's expected to have to handle -- usually accelerating to highway speeds -- and there are numerous compromises in the engine design that make it able to rapidly change power output across a wide range of power demands, all of which make it somewhat less efficient to operate in the more or less steady-state output it's called on to deliver for highway cruising.

Generally, that engine sized for peak demand during highway acceleration and tuned to be able to go from idle to maximum power and then back down to cruising throttle power over very short time spans is going to be less than the theoretical 30% Otto-cycle efficiency most places in the power band. (And chances are it's tuned to deliver maximum efficiency under the parameters of the EPA mileage tests, which the manufacturers know as well as the EPA, so no, you'll never get those EPA numbers in actual day to day use.)

The reason the hybrid concept has as much potential as it does is that electric motors have a far higher efficiency in terms of translating electrical power into torque, particularly with switching mode AC motor controllers and other high efficiency tricks, and typical battery technologies are around 70% efficient (measured as discharge/charge energy ratio), and having a battery allows the engine to be sized much smaller and in most cases run at steady-state power output while the battery handles the peak demand, so, for certain driving styles and trip profiles, the hybrid has a significant advantage. Hybrids require smaller engines because all the engine has to do is maintain charge on the battery at or below a certain break-even speed dictated mostly by drag coefficient. But how much of a differece hybrid vs conventional makes for any given driver or any given set of daily driving routes is going to depend on a fairly large number of variables, and this is true for both hybrid and conventional platforms.

So it's more complicated than just "enough hype" vs "not enough"/"too much"..

Agreed, mid-40s in miles per US gallon is pathetic indeed. I drive a diesel Mercedes C stationwagon (similar in size to the Prius V), and average at least 55mpg (US gallons) in our usual mix of driving, which encompasses comparable distances of highway, rural dirt road, suburban, and urban driving. In summer it usually gets better than 60mpg, mostly because the road conditions are less likely to be nasty. The car is almost 9 years old, and has about 320000km on the clock.

Incidentally, I live in central Finland, which has winters not dissimilar to those of Minnesota (been there, in summer and winter and in the transitions between them). Relatively modern diesel cars are quite OK in such climates; the filling stations change the diesel mix for winter to account for the cold.

Disclaimer: I own a 2007 Honda Civic hybrid.

The complaint about the Civic hybrid is that the car was sold as achieving 48/51 mpg according to EPA estimates.

With normal driving (normal = the type of driving seen every day, exhibited by most drivers), it was not possible to get much closer than 10 mpg of those figures when the car was purchased.

Now, this hybrid has a power assist design (different to the Prius), which lends itself to easily draining the battery - climbing a hill, for example - and the battery only has a limited number of power/drain cycles before it needs replacing.

It turns out that the programming on these cars was initially set to provide more 'assist' - thus improving the published mpg figures - but that has led to premature failures of the battery, leading to many warranty replacements.

Honda's response to this design dilemma? Change the programming so that the power assist is much more frugal. This reduces the cycles on the battery which makes them last longer, but means that the car now averages about 30mpg, since you have less assist from the battery when you need it.

So now, instead of having a car that is somewhat better than the non-hybrid counterpart, it is about the same at best, and has few or none of the attractive attributes that Honda used to sell the car.

We are upset at being conned by Honda selling the car as a high-performing hybrid, and later effectively remove most of the benefits of the hybrid because their design doesn't work.

Temperature has a huge effect on my 2005 Prius mileage. Below about 40 (F), the engine runs longer to warm up the catalytic converter--and even more if you want heat. Below about 20, the mileage gets worse--perhaps because I really want heat and leave the engine running while I clear the windshield.

Above 50F, I consistently exceed the rated mileage -- and even during the summer with the AC I get 48+ mpg.

There is certainly an effect of the big mileage meter on improving your driving habits.