The main differentiator between the 737-800 and its Next Generation sibling is the engine type that each one uses.

While the 737-800 primarily uses the CFM56, the Max family of aircraft are powered by the CFM LEAP 1B aircraft. The aircraft boasts a slew of benefits including increased fuel efficiency and a reduced noise level lowers the cabin volume, largely aided by the new engine.

As the fuselages of the two aircraft are similar in appearance, these engines are one of the best ways to tell the difference between the Max and 800 since the LEAP 1B engines found on the Max aircraft feature chevrons on the rear end of the housing, which helps make the engine quieter.