I am getting ready to replace the master brake cylinder on my '82 240D. The recommended fluid is DOT 4 but an autoparts salesperson told me that DOT 5 is available and is better than DOT 4 because it is synthetic.

Is it OK to use DOT 5 in a car this old? Is it compatable with the current seals that are in the brake calipers?

Thanks for any advice.

Herb
'82 240D
'87 300 SDL