One such instance is the little known fact that the new BMW 3 Series convertible has not scored well in crash testing by America's Insurance Institute for Highway Safety (IIHS).

Although the BMW 3 series scored a "good" rating in frontal offset tests, it only rated "marginal" for side impact protection. Worst still, it rated a staggering "poor" during rear-end crashes.

BMW will go to lengths to sell the new 3-series on safety, but we suspect they will not tell you about the IIHS crash test results for their new convertible.

Additionally, it can be safely assumed that BMW will not disclose the fact that the Saab 9-3 convertible scored very well in the same series of tests. The Institute president Adrian Lund described the Saab 9-3 convertible as "impressive" in respect to its performance during the crash tests, because the 9-3 scored "good" for protection in front, side and rear crashes.

Lund also praised the whiplash protection offered by the Saab's head restraints in rear-end crashes.

“We wanted to test convertibles because sales are increasing,” Lund says. “We also wanted to evaluate a group of vehicles that automakers wouldn’t expect us to test to see if crashworthiness improvements in mainstream cars also are being built into convertibles. For the most part we found that this is happening.”