Why do you want to use 0W40?
The 40 weight spread requires an ENORMOUS amount of viscosity index improver additive in the oil. This additive causes severe carbon build up, especially in small hardworking engines. Be careful.
Unless you drive up into subzero temperatures in the mountains and then back into the desert on a daily basis, this weight oil should be totally unnecessary.
Best of luck,
'01 C Class, Six Speed
'84 Euro 240D, manual, 533K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in