1984 300SD

1. do these cars have LSD?

2. around what rpm should the engine be when u are cruising on the highw at 60MPH? (i am paranoid that mine is a lil high)

3. how often should u use diesel purge?

4. does any normal steering wheel cover found at common car places fit mercedes?

these been bugging me for a while, thanks

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198? 300D ???K - Future DD
1989 300TE 285K - traded in '12
1984 300SD 186K - Sold in 08
1978 300SD 330K - Died in 05