Here's what one straight-6 looks like. That's the m103. The last straight-6 by MB was the m104 if I'm not mistaken.

Just means that the cylinders form a line (or an "I") instead of a "V" shape if you were to look at the engine from the front.

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1990 190e 2.6 - The only one I can really call "My Car".

1987 190e 2.3 - The donor car's up and running, only mods are Euros and a Sony headunit. My Dad's runabout now.

1990 300e 2.6 - The parents' ride.