That's what I figured. Having been around engines and vehicles most of my life, engines with an odd number of cylinders are not balanced as well as the V-6 or V-8 or even inline engines.
I have a neighbor who works for a Dodge dealer and he said the same about Dodge's two biggest mistakes.
#1. Rushing to be the first with a V-10
#2. The PT Cruiser
Actually engines with odd numbers of cylinders can be dynamically balanced better that even numbers of cylinders.
Inline 4's have an inherent dynamic imbalance (I think they call it a "secondary rocking couple"). I've seem both Kawasaki and Mitsubishi use a counter-weight shaft to counteract this.
Actually the inline 6 is the most inherently balanced engine configuration available! More so than any V configuration. According to M. J. Nunney (Light and Heavy Vehicle Technology, Fourth Edition), “The straight-6 layout is the simplest engine layout that possesses both primary and secondary mechanical engine balance, resulting in relatively low manufacturing cost combined with much less vibration than engines with fewer cylinders.” The best engines ever made were inline sixes; The AMC 258, the Dodge slant six, the Ford 4.9L 250, the Chevy 4.8L, the Cummins diesels, and BMW’s inline sixes. The 5 that Chevy offers is the same as the inline 6 that comes in the Trailblazer just minus one cylinder. I get about 19 city and 23 highway in my 2006 Colorado 4 door 2WD Z71. It makes way more horsepower than my Z28 did in 1979! I am concerned over the cylinder head issues though, but I haven’t had any problems yet at 38,000 miles. My dream truck though is a Dodge Ram Cummins 2500 Mega Cab... a superb engine wrapped in crap!