This old iron engine is noted for very long life and for not being really picky about oil used.
Certainly one of the best engines ever installed in any Mercedes, including the sainted diesels.
What specs does this inexpensive Techno oil claim?
If it meets decent specs, use it and enjoy the savings.
In general, a 5W-40 is a better choice than a 10w-40, since it's usually a better oil.
OTOH, if this engine has run happily for decades and many miles on 10W-40, why try to fix what isn't broken?
Certainly one of the best engines ever installed in any Mercedes, including the sainted diesels.
What specs does this inexpensive Techno oil claim?
If it meets decent specs, use it and enjoy the savings.
In general, a 5W-40 is a better choice than a 10w-40, since it's usually a better oil.
OTOH, if this engine has run happily for decades and many miles on 10W-40, why try to fix what isn't broken?