Hi,

I have a 1990 MB 300E and have Bosch HR9DC+ (#7978) Spark Plugs currently installed in my car. I received a couple of boxes of Bosch HR9DC (#7578) and was wondering if it was ok to use these for my next tune up? What is the difference between the two?

It seems that they might be old stock.....I am just guessing because they are not "+".

Any information would be greatly appreciated!

Bob