Is Cummins' diversity helping it weather the storm? Image source: Cummins analyst day
presentation, November 2015

Cummins' (NYSE:CMI) strong run up this year has fueled much interest among investors: The stock has gained 17% year to date as of this writing. Comparatively, rival Caterpillar (NYSE:CAT) is up only about 6% so far this year. Noth companies are cyclical with common end markets, and are aggressively restructuring to emerge leaner and stronger when the business cycles turn. However, subdued commodity prices are keeping Caterpillar investors cautious.

That's not to say that Cummins has left the worst behind. While the bulls have several reasons to be excited about as I highlighted in a recent article, the bears may have an upper hand given the massive challenges facing the engine maker going forward. For instance, did you know that Cummins' key engines customer, Paccar (NASDAQ:PCAR), is turning out to be its biggest threat right now? Or that Cummins' primary trucking market is showing signs of stress? Go through the slideshow below to get the full picture, including the answer to whether Cummins is a buy now.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.