You can buy any brand of spark plug you want. Leave them in the box they came in, put them in the trunk and you will never have to change them ever.

Seriously, the above suggestion is a good one. Diesels don't have spark plugs. They use glow plugs. Get yourself a basic manual and and owner's manual and read about the car. The maintenance manual that comes with the owner's manual packet also is a great way to learn when and what routine maintenance tasks need to be done.

Len
'83 240D 345,000 miles original owner