When my in-laws traded in their car for a Prius a few years ago, I initially wondered if they were trying to save money on gas or if my retired father in-law simply wanted a new toy.

I'm a sucker for gadgets and new technology too, so I certainly couldn't blame him if he did. But by 2008 it didn't matter if gadget lust had driven the trade, because they were saving $100 a month or more on gas.

Consuming more and more
Of course, oil and gas are quite a bit cheaper now than they were last summer -- when the world struggled to cope with $147-a-barrel oil. My in-laws aren't saving nearly as much now, but I suspect they'll continue to be happy with their trade in. Toyota (NYSE:TM) should be pleased with sales of the Prius, because as the world recovers from the recession in oil consumption, emerging markets should once again put pressure on global oil supply to grow.

The table below shows just how big a factor consumption growth in emerging markets has been in the last 10 years -- and how little developed market consumption has changed.

Oil Consumption – Millions of Barrels/Day

Country

1998 Consumption

2008 Consumption

Rank

CAGR

U.S.

18.9

19.4

1

0.3%

China

4.1

8.0

2

6.9%

India

1.8

2.9

5

4.9%

Germany

2.9

2.6

6

-1.1%

Brazil

2.1

2.5

7

1.8%

Saudi Arabia

1.4

2.4

10

5.5%

World

74.1

85.4

N/A

1.4%

Source: Energy Information Agency actual and forecast data; CAGR = compound annual growth rate.

Regardless of what happens to U.S. consumption, it's the emerging markets that are creating the need for additional supply. And China's consumption clearly stands out from the pack.

Expect more of the same from China
The Energy Information Agency expects China's consumption in 2009 to be flat, largely because the recession has pushed industrial use down. With most of its GDP tied to exports, an industrial recovery will take time. But transportation consumption is another story, as China continues to sell autos at a breakneck pace. Last month another 812,000 autos were sold in China, and the country is on pace to sell more than 10 million autos this year. That's on top of last year's 9.3 million autos sold, and higher than 2009 sales expectations for the U.S.

Volkswagen has announced that it expects its 2009 sales in China to exceed its sales in Germany for the first time. Volkswagen's probably not alone either, at least not for long, because only 20 out of 1,000 people have cars in China. That compares to 800 or so per 1,000 people in the U.S. With such little consumption per capita, there is plenty of room for additional growth over the next five to 10 years. As more cars hit the road, China's oil consumption will continue to increase.

That's good news, not just for PetroChina (NYSE:PTR), but for multinationals like ExxonMobil (NYSE:XOM), Chevron (NYSE:CVX), and BP (NYSE:BP), because they need steady cash flows to support the development of new fields. And it's even better news for Suncor (NYSE:SU), Petrobras (NYSE:PBR), and other firms with substantial oil sands and deep-sea assets, because these sources are substantially more expensive to develop.

All this means that despite the recession and the recent run-up in oil stocks, it's not too late to buy oil, because the long-term trends for higher demand are still in place.

China set to grow and benefit too
For its part, China needs to reduce its reliance on exports and deal with the inevitable cultural and political changes that come with economic growth and greater freedom. But because of its substantial currency reserves and infrastructure spending over the past decade, it is in a position to continue supporting the fastest economic growth story in recent history.

China's potential growth is one reason our Motley Fool Global Gains team is heading back to the country this July to meet with some promising companies we've identified through our research. If you're interesting in hearing about what we find, you can sign up to receive all of our free real-time dispatches from the field simply by providing your email address in the box below.

Nathan Parmelee is co-advisor of Motley Fool Global Gains, whose twitter feed you can follow at http://twitter.com/TMFGlobalGains. He owns a few energy companies, but none of the companies mentioned in this article. Petrobras is an Income Investor recommendation. The Fool has a disclosure policy.