The giveaway is the distinctive flat front cab-over-engine ... a 2015 Western Star semi-truck. Both of these trucks are noticeably more muscular than the Freightliner FL86, and probably were ...

The original design, as seen in the Transformers animated series, was based on a Freightliner FL86 cab over semi-truck. Personally, I much prefer that original Optimus Prime over Michael Bay’s ...

The semi-truck that inspired the original Optimus Prime is possibly a Freightliner, particularly the 1980 FL86 model. While this isn't a confirmed fact, it's generally accepted among fans.