Just changed the oil on a 3.0 diesel merc and now the engine rattles under load until the oil/engine is hot. Used fully synthetic 5w40, previously tried 5w30 both recommended the 5w30 was worse.
Both oils spec'ed to MB oil numbers.
Previously car was fine from cold on the old oil, no idea what it was.
Should I just not worry about it given the numbers are to spec ?
Cheers Vin
Possibly mineral based 10w 40
Not sure if that's correct, multi grade mineral oil is not recommended for diesel engines as it has a detergent content.
10 40 was the standard grade spec for oils in desiels, you had two different types one for petrol another for desiel .
If 10 40 was put in the car it would certainly stop the rattling on startup, one of the tricks of the dodgy car dealers was to put heavier oil in the engines to deaden any rattle
It depends why it was rattling; thicker oil *may* reduce the noise if it's a low oil pressure problem, but not necessarily in other cases.
Chris
Yep I think that's correct. You couldn't just slip any multigrade into a diesel for the above reason. I used just used a straight grade oil.
Modern diesels have far less tolerance and are built for synthetic oils which have universal application.
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