Borrowing cars from a foreign partner is becoming popular. It saves money and is a fast way to fill the model lineup. But that doesn't mean it will work.

Look at these monthly sales figures for the Saab 9-2X, the “Saabaru” — a Subaru WRX transformed into a Saab.

Feb. 2005 161
Jan. 2005 205
Dec. 2004 438
Nov. 2004 290
Oct. 2004 334
Sept. 2004 316
August 2004 226
July 2004 135
June 2004 48

Skip June's start and it's an average of 255 sales a month. That looks like a flop to me.

General Motors embraces the concept: After the 9-2X comes the new Saab 9-7X, the Saab SUV derived from the Chevy TrailBlazer.

There will be another Saab/Subaru SUV in the future, too. Then there will be a front-wheel-drive Cadillac for Europe, built off the Saab 9-3 line in Sweden. That same GM Europe Epsilon architecture underpins the Opel Vectra and Chevy Malibu.

Likewise, Ford seems eager to build everything off its Japanese Mazda6 and Mazda3 platforms.

This borrowing or badge engineering won't work much of the time. When done well, yes, it succeeds. Until the '60s, GM was the industry leader using just two platforms, one for Chevrolet, Pontiac and Oldsmobile and another for the luxury models.

But there was just one basic Chevrolet then and one Pontiac, not the 20-plus Chevys and nine Pontiacs of today. With just two platforms, there was money and talent to build in differences among the models. Engines and suspensions were different. The cars looked different. This is impossible when there are 10 platforms to differentiate.

To succeed, the vehicles really must fill some need. Cheap, fast and foreign isn't enough.

That might be the problem with the Saab 9-2X. For one thing, the borrowed vehicle usually costs more than the original. Subaru isn't going to give away its WRX, and GM wants to make a profit, too. Will buyers pay extra for some sheet metal changes?

Some predictions:

  • The 9-7X will do better than the 9-2X because the market is stronger for SUVs than cars, and Saab has none of its own.
  • The CaddySaab (Cadillac BLS) goes on sale next year and won't fool anyone. If GM wanted to make an impression in Europe, it should have sent in the CTS, not a dolled-up Saab.
  • The Ford Fusion coming this fall, off the Mazda6 platform, won't do as well as Ford thinks. The car is smaller and probably will be more costly than the Taurus it replaces.

Advice: Rethink global borrowing. How much money is saved if the stuff bores the customers, and they go to Toyota anyway?

For years, we've been hearing from Detroit about money saved — money saved buying Fiat, buying Jaguar. I don't believe it anymore. GM just spent $2 billion to get rid of Fiat — did GM save anything on that deal?

Reduce the number of platforms in the U.S., freeing design teams to create differences among American models built off American architectures, as in the old days. Build vehicles that excite Americans, not vehicles that can be twisted from some foreign architecture.

Jerry Flint is a columnist for, and a former senior editor of, Forbes magazine.