Rust is a bigger issue on the W115 as on the W123. Not only are they older but they were much more rust-prone than the W123. I personally prefer the styling of the W115, but parts are a bit harder to locate in some cases. Engine, whether it's the 4 or 5 cyl, is the same as in the non-turbo W123, except for the layout of the accessories.

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Denis

1979 300TD 189,000 Miles, now running WVO with a home-made 2 tank conversion
1974 230 Gasser 189,000 Miles, For Sale
1961 VW Microbus 162,000 Miles
1961 Ford Fairlane 500, 53,900 original miles
1951 Oliver Super 55 Tractor
2002 Chocolate Lab