Sabres are rattling in Detroit, and I'm not talking about the chatty dashboard on my buddy's old Buick LeSabre. I'm talking about tough talk from the United Auto Workers union regarding a prospective deal with ailing GM (NYSE:GM). While headlines earlier in the week hinted that GM management had tried to force a deadline for the union to come into some kind of compromise on splitting health-care costs, the union fired back shortly thereafter, when UAW President Ron Gettelfinger told WWJ News Detroit, "We're not confident at this juncture that we need to do anything.''

GM investors should know what's at stake here. Gettelfinger wants what belongs to shareholders, and he's clearly trying to use it as a bargaining chip on the national media stage. As he put it, ". They're paying dividends, they've got a huge cash reserve . " In other words, he thinks the profits and assets belong to the workers. We can expect no better from a union leader, but knowing that his desires are out of line won't help shareholders if he forces GM's hand and the spit hits the fan.

And it just might. On the management side, recent remarks by CEO Rick Wagoner have been interpreted as a threat by GM to unilaterally roll back health-care coverage. That kind of action would surely result in a strike, crippling GM at it most vulnerable moment in years. So it was probably just macho bluster meant to please shareholders. Still, the roosters strut and caw before they start to claw.

With GM's credit rating -- along with Ford's (NYSE:F) -- recently cut to junk status, the borrowing that's the firm's lifeline is only going to get pricier. Sales are already slumping, to the point where the firm has pulled out all the stops and offered its "employee discount" to anyone in the entire U.S. And we thought we'd already seen the depths of GM's desperation with the ever-increasing cash back offers.

So here's my Foolish question: Why would anyone pay for a piece of this business?

I'm not saying you couldn't make decent money on GM stock these days: A buy in mid-April sold now would net you a cool 40%. But I am saying that this is a very crummy business. And let's just say that all GM investors should be burning a candle to Saint Kerkorian.

It may be comforting to invest with a successful billionaire, but here's the harsh truth: GM is absolute investment-grade junk. In the last five years, the average return on capital comes to a whopping 1%. That's lower than you'd get packing your money into a crummy savings account. At the same time, sales have been barely above flat and earnings have sunk. And this isn't a new kind of failure. This is just the way GM works. That's why the long-term chart is such a fright. How'd you like to make nothing since the '70s while the S&P 500 returned better than 1,000%? If that's your twisted idea of a good time playing the market, then GM's your daisy.

If I came to you with a business with this kind of track record for failure -- and a hard-headed labor force determined to make sure that any potential success was very slight -- you wouldn't buy it at any price. But slap on a GM badge and suddenly you're more sanguine?

Keep that in mind when you consider whether or not to buy these shares. They might go up, and they might not. The outcome is a crapshoot. That's why the smart money will be looking for better opportunities altogether. If you have to have cars, how about Toyota (NYSE:TM)? How about Honda (NYSE:HMC)? You know, companies that know how to turn a profit consistently?

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Seth Jayson is used to angry email from the GM faithful, but he'll stick to investing in companies that can produce better returns on capital than a savings account. At the time of publication, he had no positions in any firm mentioned. View his stock holdings and Fool profile here. Fool rules can be found here.