a very VERY big x2. i actually frequent that website more then this one. i was gonna bring it up but just figured it'd be wasting my time. some people here seem to "stubborn" to learn new tricks
when looking at viscositys, the first number is the cold weight, and the second number is the weight at operating temps. when you start your car, your oil is either a 5 or 10w (or very close). obviously the 5 is thinner and will flow better NO MATTER WHAT. when your engine gets up to operating temperature, they're both 30 weights. so theres no difference. you could run 5w30 in your grand prix all its life and the only thing its gonna suffer from is better lubrication at start up