I know folks who swear by Diesel rated (not based) oil in their M104s.

I’ve never had an M104 but I believe the replaceable filter element is in a canister off the driver side rear end of the engine. Most likely under a cover with a couple of nuts that take a 13mm wrench. If you have the equipment to extract oil through the dipstick tube, you don’t need to get under the car for an oil change.

Temp gauge looks good.

Sixto
98 E320s sedan and wagon