At first I thought that all W140 diesels were 350SD. On EBay I saw a 1993 diesel W140 diesel listed (the badge on the boot lid was 300SD) as a 300SD. Please help me as I am an ingorant moron outside of W123's and W210's.

Seems the name was changed to 300SD because the 350SD had engine problems with bent rods. The engines are basically the same as the '90-'91 350's. I think some minor upgrading of the connecting rods maybe, but really the same engines.

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1979 300SD 83k miles Astro Silver Metallic/Black leather #3447
1990 350SDL 202k miles (3L engine from an 87 300D)Black/Grey leather
2006 Pleasure-Way Class B MoHo (Sprinter chassis) 134k miles
2005 E320CDI 270k (car is sooo fast - I can't believe it's a diesel!!!)

I'm quite sure that M/B did not change the designation due to bent rods on the W126. For reasons unknown, the W140 carries the "300SD" designation in the model years 1992 and 1993 even though it has the identical 3.5L engine that's in the W126.

I think they were trying to go for round numbers. The 400SEL is actually a 4.2, so I think they just liked the sound of 300,400,500,600 for their S class range...

Seems lots o folks think its a diff engine.

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1979 300SD 83k miles Astro Silver Metallic/Black leather #3447
1990 350SDL 202k miles (3L engine from an 87 300D)Black/Grey leather
2006 Pleasure-Way Class B MoHo (Sprinter chassis) 134k miles
2005 E320CDI 270k (car is sooo fast - I can't believe it's a diesel!!!)