The W123 body wagons, like the one you are looking at came with both turbo and naturally aspirated engines. I think the turbo is rated at 125 HP or so. You should be fine on the freeway, both engines can cruise at 80 all day.

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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine