940 Engine Oil.

[zimbodel]

Lots of oil threads but nothing addresses modernizing the original oil specifications that is quite out of date.

I have the service manual, but the oils and fluids specified is real old and outdated.
I know of course to find a similar oil, but my question is about full synthetics.

Regarding engine Oil.

I use 0W40 in my Mercedes Benz cars and they are already over 300,000 miles. The engines are as-new.

My volvo 940 is also around there now, and I am wondering if I can use 0W40 as most european cars are prescribed to use.

Or, is there a very good reason to use a specific oil for a 940 Red block high mileage engine ?

[jimmy57]

Ow40 is a good choice for that engine unless you are in over 100F temps where 5W40 would be my choice, even 15w40. That engine uses connecting rods with 3+ mm side clearance and relies on the pistons to keep rods in center of journals on crankshaft. Thicker is better in this case. The valve clearance is on the wider side and the modern thin stuff makes the tappet commotion much louder.

[zimbodel]

Thank you for that very detailed explanation. summers do get in the 90s but it is short lived. Winters get darn cold. So 0W40 seems to be right according to you. If you have anything better you feel will help protect the engine let me know, but it is good to know that 0W40 that served me so well with the MB's will work with the 940.

BTW: I find this info amazing

connecting rods with 3+ mm side clearance and relies on the pistons to keep rods in center of journals on crankshaft.

That is quite an unexpectedly large/huge clearance.
I wonder if they did that to tolerate dirty oil better than engines with extremely tight tolerances and thereby by design get longevity?
If what you say is true, then too thin oil is likely going to be the end of a redblock as there will be more wear.