Quote Originally Posted by psychos2
Why would the blue top not be good for starting a car?
My statement was incorrect and based on outdated information. I've just learned that the 34M Blue Top is a 2nd generation Optima and is constructed to the same standard as the Yellow and Red Top batteries.

The original Blue Top, from what I understand, was built a little lighter (less vibration in typical marine environment) and formulated more toward a traditional deep-cycle usage curve. The popularity of this particular model in the RV market is what likely led to the improvements.

Sorry for the error on my part!