Funny how the posts come at appropriate times. I put in a set of Champions yesterday in my 300E. It's what they had, Bosch weren't handy. The manual says .032. I opened them to .035, even this sounds like something left over from the point ignition days. They were factory set at .040. It wouldn't seem that there would be a down side to opening them up to .040 or even greater.
I pulled out a set of Bosch platinum that had opened to .060 and the engine was running decent. I'm ashamed to say how long these plugs were in there.
Any comments about factory spark plug gap specs?
'84 Euro 240D, 523K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in