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By most accounts, the conventional gasoline engine's days are numbered. Long before electric听听become commonplace, automakers expect to wean themselves off gas-powered powerplants, replacing them with fuel-efficient alternatives.

On Monday, Ford's Joe Bakaj told听听that the time is coming when most Ford vehicles will come with either a diesel or an EcoBoost engine, the latter of which relies on turbocharging,听direct injection, and other innovations to wring mileage from every drop of gas.

Then on Tuesday, Volkswagen said essentially听, claiming that within three or four years, every听听in VW's lineup will be either a turbo or a diesel.

And even before these grand pronouncements, we saw this trend migrating across the entire auto industry. Have you looked for a V8 lately? The shift toward smaller, tech-heavy engines has played out in family cars, luxury rides, and even performance models.听

THE GOOD, THE BAD

Obviously, turbos and听听have a number of benefits -- otherwise, automakers would be far less enthusiastic about the switch.

For starters, they're efficient. Diesels, for example, operate at high temperatures. That means that more of the听听that's pumped into the engine is burned, which boosts output. (Nifty bonus: diesel engines tend to last much longer than conventional ones.)

Turbochargers, on the other hand, force additional air into an engine's combustion chamber. That boost of air means an increase in combustion, which translates to an increase in efficiency: less gas is wasted and more is converted into energy.

Even better, a turbocharged engine is lighter than its traditional counterparts. For example, properly designed, a six-cylinder turbo can eke out about the same power as an eight-cylinder conventional engine. So, not only does that engine offer a boost in efficiency, it makes the vehicle lighter, which means the engine doesn't have to consume as much fuel to move it. That's like a double-whammy of fuel economy.

All of this helps automakers meet the increasingly strict federal regulations around fuel efficiency. But there are a couple of downsides.

Turbo engines are more complex than conventional ones. And the more parts something has, the more likely it is that one of those parts will break. Designs have improved over the years, but they're not perfect.

Ironically, Ford's EcoBoost is a perfect example of this problem: though it's increasingly popular, many consumers claim that the EcoBoost has left their vehicles with significantly reduced power that's much worse than the traditional "turbo lag". In Ohio and Louisiana,听听for that, and last spring, the National Highway Traffic Safety Administration听.

Diesels present a different challenge -- one of public perception. Many Americans associate diesel engines with the loud, foul-smelling cars that became popular during the 1970s and 80s. Though diesels are very popular in Europe and elsewhere, Americans have a tough time thinking of them as the clean, elegant, sporty vehicles they've become over the past couple of decades. So as much as they have to offer, we're not sure that many in the U.S. will be inclined to buy them.听

Do the pros of turbos and diesels outweigh the cons? Sound off below -- or sit back and watch as the great migration begins.

And be sure to check out Green Car Reports' take on听听and听. They offer some very interesting perspectives on these and other matters.