Why do American semi-trucks (18 wheelers etc) exclusively use inline 6-cylinder engines, no matter if it’s a Mack, Detroit Diesel, Cummins, or Volvo-built engine?

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I get why they are diesel, but why are they all of the inline 6-cylinder configuration? Why not V6 or straight 8 or freakin huge inline 4-cylinders?

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Anonymous 0 Comments

TIL semi trucks use 6 cylinder engines. To be quite honest it’s not something I’ve ever even thought about. What kind of displacement do these I6s have? They must be massive.

Anonymous 0 Comments

I had an Inline-6 Ford F150. Great truck. I understand the Inline-6’s were also used on Farm Tractors.

Good engine.

Anonymous 0 Comments

An inline six is the “workhorse” of engines for a few reasons, but mainly because of TORQUE and RELIABILITY!

A straight 6 cylinder can put out more torque at a lower RPM than a Vee 8 cylinder. This is because the rotating mass of the crankshaft and piston rods of an I6 are greater than a V8. More rotating mass = more low end torque for moving heavy loads.

RELIABILITY! Fewer parts means fewer repairs. An inline 6 can out pull a V8 and it can do it with about 40% fewer parts. The design of the I6 rotating assembly gives it inherent primary and secondary balance, so it runs nice and smooth which reduces wear.

At the end of the day the straight 6 is the perfect combo of power, reliability, and cost of operating.
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