as you can see, nobody wants to answer this question, because it is too freaking difficult. i mean, which month? july or june? how can one choose? june has arguably nicer temps, but july has the 4th of july -- really the only summer holiday worth spit. both are excellent months for cookouts, but depending on where you live, you might have crappy weather in one month or the other. it's completely too difficult for this question to be answered in an "absolute truth" sense without further research. therefore we will have to dig a little deeper into the minds of completely random sources. observe.
according to this
source, "July Class 8 truck sales in the U.S. were up 6.7% vs. June, but were down 5.1% compared to July 2002"
it seems that july is a superior month in 2003, but perhaps in 2002, things were not so good. these results are still inconclusive. moving right along...
another
site says "TSMC, UMC July sales: no better than June" whatever the hell that means. once again, completely unhelpful. i suppose it will all come down to the next completely random source.
when searching for "best month ever" on ask.com, nearly every single result had something to do with JULY being the best month ever for car sales: honda, bmw, etc. it seems that everyone likes to buy a car in july to be ultra patriotic or something.
AND THEREFORE JULY IS THE ANSWER
honda or bmw