I had an interesting thing occur yesterday as I was coming back from a long trip in my 240D. I always get my diesel at Chevron but yesterday I had to get it at this truck stop as I couldn't find anything else. Right after I filled up and left I started hearing a "pinging" or "knocking" sound coming from my engine. It made this sound under both acceleration and cruising speeds. I still have half of this batch of diesel left in my tank. My car NEVER made this noise before I filled up at this truck stop.

I guess you could describe the sound as if someone were taking a hammer and hitting it on metal to make a high-pitched "ping" sound.

I put in 12 oz of Marvel Mystery Oil with every tank of diesel and I do mostly highway driving with my car. Any ideas as to what is happening? Damage done?

thanks for the advice and help.

PS--I am 100% sure I put diesel in for those who may wonder if I put gas in by mistake.

mike