don't do it.

it's the same as 15w-40 when hot.

And when cold it will be too thick and could damage your engine. I think the thickest single grade oil that mb recommends is 30 weight.

find some diesel rated 20w-50 or 15w-50. the latter number is the hot viscosity.

But as we said before it's not a real fix and you will still have a leak.

Other things that make oil leaks worse: plugged pcv system or a hot running engine