You know what they say: Buyer, beware. And if an offer sounds too good to be true, well – think long and hard before accepting it.

I went shopping for a new car in Ottawa this month, and was astonished to be told by several dealers that I could save thousands of dollars by borrowing instead of paying cash.

The deal that several General Motors dealers offered was this: I could buy a brand-new Equinox or Malibu, each costing close to $30,000 when taxes and dealer charges were added, and borrow the entire amount interest-free.

Not only would GM lend me the money interest-free, but I would also have six years to pay in two-week instalments. That's zero-per-cent interest for 72 months. That puts you behind the wheel of a $30,000 car for less than $100 a week.

By one dealer's reckoning – assuming an interest rate of 8.9 per cent, which GM was offering to finance some of its other models – I would save about $8,500 in interest over the six years if I bought a Malibu or Equinox.

But, I inquired at each GM dealership I visited, what discount would I get if I paid cash? None, I was told.

"How can that be?" I wondered. Surely GM must inflate the purchase price to cover the cost of that interest-free loan. Someone must pay those costs, and it can't be General Motors, already reeling from a $15.5-billion loss in the last three months.

The answer, of course, is that this interest-free loan is the latest 'incentive' from GM to boost sagging sales, and get consumers to splurge on an expensive new vehicle without the hardship of saving for it. The hardship comes later, in making those pesky payments every two weeks.

The consumer has no way of knowing for certain whether there's really a cost for that six-year, interest-free loan. True, it would have cost the same amount – at least, when I inquired – to buy those vehicles as it would to opt for an interest-free loan.

But, in two of the GM dealerships I visited, salespeople drew my attention to other models in the showroom when I made clear I was looking to pay cash, and would not buy a Malibu or Equinox without a substantial discount on the price that came with an interest-free loan.

One dealer I visited had a new Uplander minivan sale-priced at about $16,000 before taxes. But that price was only available to consumers who paid cash, a salesperson explained.

The Uplander was also available with six-year, zero-per-cent financing. In that case, the purchase price was about $5,200 more, the salesperson said.

That is in line with what I would expect – the $5,200 approximately making up for lost interest.

Asked for GM's policy on low-interest or no-interest financing, company spokesman Stew Low told me: "The Canadian auto industry is an intensely competitive marketplace. The vast majority of Canadians choose to finance or lease their vehicles rather than pay cash. GM is competitively positioned from both a price and payment perspective compared to our competition.

"There are numerous examples where significant cash credits are available in lieu of zero-per-cent, 72-month financing," he continued. "There are other examples where significant cash credits are available in combination with zero-per-cent financing."

But I had no interest in buying a minivan, and decided this was not a good time to pay cash for an Equinox or Malibu.

The six-year, interest-free loan appears to be the auto industry's solution after its recent discovery that car leasing can prove costly to car makers. Many manufacturers have scaled back on leasing, dropped it altogether, or made it much more expensive for consumers.

GM and other manufacturers have been burned lately because some vehicles, returned after having been leased, weren't worth as much as the car makers calculated.

Leasing never made much sense to me as a consumer. I thought most leasing deals were weighted in favour of the manufacturers. And those who lease – rather than own – their vehicles switch to a new vehicle more frequently, which greatly increases their annual expenditure.

But it turns out some consumers who lease have been getting a very good deal lately. This is especially true for the most notorious gas-guzzling vehicles. In some cases, analysts say, those who leased such vehicles were undercharged by as much as $10,000 over the term of the lease. That's because the vehicle depreciated, while leased, by up to $10,000 more than anticipated.

When you think about it, a six-year, interest-free car loan is very similar to a six-year lease. The difference is that, after six years, you get to keep the car rather than hand it back to the manufacturer or leasing company. Of course, it probably won't be worth much after six years.

The bottom line: if you are a fan of leasing, get the best deal you can on a six-year, interest-free car loan. If paying cash, or making your own financing arrangements, seek out a deal that rewards you for not taking a low-interest, or no-interest, loan.