Let's imagine for a second that you have a family, and you need a vehicle to transport them around in.

However, you're also looking to get a good mix of practicality and gas mileage, as gas prices aren't making those long vacation trips any easier.

Your eye may have been caught by the 2012 Toyota Prius V wagon - you know the Prius name stands for low emissions and high economy, but there's now a bit more space. But what could it save you over a typical wagon rival, like the 2012 Mazda5?

We're comparing the Prius V and the Mazda5, the latter fitted with the automatic transmission. It's no less economical than the manual option, and easier to drive when the kids are kicking the back of your seat, screaming, "Are we there, yet?"...

Economy and performance

No guesses on the most economical here. Thanks to its gasoline-electric full hybrid system, the Prius V sets new standards in the class for gas mileage.

The EPA quotes city mileage of 44 mpg - over double that of the Mazda's 21 mpg city. Highway mileage is 40 mpg versus 28, and that all results in the Prius V managing 42 mpg combined, versus the Mazda's 24 combined.

If we use the EPA's figures of 15,000 miles per year, 45 percent on highways and 55 percent city, the Prius will cost you $1,243 in fuel, at an average of just under $3.50 a gallon. By comparison, the Mazda would guzzle $2,175-worth of gasoline - $932 more.

The Prius V would also require less frequent stops as a result. Even though its 11.9 gallon gas tank is smaller than the Mazda's 15.9 gallons, you'll get an estimated range of 450 miles, rather than 343. All the better for making progress to your destination.

The 5 hits back with better performance from its 157-horsepower 2.5-liter engine. The 5-speed auto lets drivers have some control over when they shift too, so it may suit those looking for a sportier drive.

Equipment and practicality

The two cars are quite evenly matched in terms of passenger and cargo volume. Both the Toyota and the Mazda offer the same 97 cubic feet of passenger space, in their first and second rows.

The Mazda actually has one more seat than the Prius V, as it uses three rows of two seats, instead of the three-seater bench in the Prius. With those rear seats stowed, the Mazda has 44 cubic feet of cargo volume, to the Prius' 34 cubic feet.

That does mean the Mazda's cargo volume is compromized when the rear seats are in use - not a problem in the Toyota.

Both cars have plenty of equipment, and safety and security levels are also good - these are both cars you should be confident of carrying your family in.

2012 Mazda Mazda5

2012 Mazda Mazda5

Price and costs

A basic Mazda5 in the lowest Sport trim level, with the automatic transmission, has an MSRP of $20,625. This compares favourably with the basic Prius V "Two", which starts at $26,400.

For that price, you could buy a top-end Mazda5 Grand Touring with Xenon lights, a glass moonroof, SIRIUS satellite radio and more, and still have around $2,400 in change.

The Prius does get Toyota's Smart Key system and a backup camera for that, but otherwise they're similarly equipped.

Given the yearly fuel savings above, you'd only need to own the Prius for around two and a half years before it paid off the difference in fuel savings alone - or around six years, comparing base model with base model.

Neither figure is too unrealistic, and 2.5 years in particular is quite a reasonable payoff - every subsequent month would be in your benefit, not to mention that of the environment.

Conclusion

While the lack of six or seven seats in the Prius may put off some - but if you really, truly need seven seats, you're into a bigger class of crossovers and wagons, and the only hybrid with seven seats this year is the 2012 Toyota Highlander Hybrid. This considered, the 2012 Toyota Prius V is clearly capable of making back the initial outlay in fuel savings over the Mazda.

You may have to sacrifice a little bit of equipment, but if you plan on keeping the car for some time then you could always spend a little extra to get an even better-specced Prius. In terms of cargo and passenger volume, you don't lose much to the Mazda either.

While the Mazda5 is undoubtedly a good car, it's interesting to see just how much you could save by taking the Hybrid option.

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