Buying a used GM car right now is a good idea even in the middle of what sometimes seems like a catastrophic series of events for the car company. It is important to keep some keys facts in mind and be aware of some of the myths being thrown around.

1. FACT: Sales for GM’s new cars set a high in May (up 18% from April 2009 by core brands: Chevrolet, GMC, Buick and Cadillac) while GM Certified Used Vehicles, the industry’s top-selling certified brand May sales down 28 percent from May 2008.

What this means: As buyers rush to grab new GM cars, the used (but manufacturer certified) models are getting less love and dealers always love sales so negotiating a sweet deal on a 2008 or prior under their Certified program is in season.

2. FACT: Warranties on GM’s Certified Pre-Owned will still be supported by certified dealers and service centers.

What this means: According to Mark LaNeve, VP of GM North America Sales & Service, ” We will honor our warranty commitment given at the time of purchase to owners of current and future General Motors Certified Used and Pre-Owned Vehicles, such as the 12-month/12,000 bumper-to-bumper warranty for Certified Used and Pre-Owned vehicles, and focus on the customers’ needs from their sales to service experience.” Extended warranties are not always backed by the manufacturer and are sold on behalf of third party companies so those companies are responsible for claims.

3. MYTH: Leftover 2008 and previous years models have been sitting on the dealer lots and could suffer from “Lot Rot”.

What this means: Pretty much nothing because it is a bit of an extreme urban myth based on an interesting article about cars decomposing in landfills which states that metal head gaskets can begin to rot after 1 to 3 years. What they really mean is that rot can be accelerated if exposed “…to high moisture content, acidity and dissolved salts in the soil”. In other words, buried in the ground. Moving on.

4. MYTH: Your local GM dealer is closing as part of GM’s restructuring plan (or “reinvention” as GM likes to call it) so you will not be able to get your Certified Pre-Owned car serviced once they close.

What this means: GM vehicles will receive service and warranty work at closing dealers until they shut down. The remaining dealers will continue to provide service and warranty work and so you may have to drive a little further but there will still be twice as many GM service centers as Toyota centers.

5. MYTH: Hummer is going away but you can finally get the biggest vehicle of your dreams for little to no money.

What this means: Hummer is being tentatively being sold to a Chinese company who is expected to maintain Hummer service and sales after the contracts are completed for the brand’s ownership transition and although the perception is that Hummers are rotting on the lots, May sales for Certified Pre-Owned Hummers were the only GM Certified Pre-Owned brand saw an upswing in May (up 16%) Mind you, that was only 222 total vehicles across the country because those suckers still have a dollar sign as big as their carbon footprint.

Which car from GM’s Certified Pre-Owned inventory would I want? Well, I certainly wouldn’t say no to a Cadillac CTS.