Rotella T 15W-40 dino or Valvoline Maxlife 10W-40 for 97 M119, 105K miles?
 

I just got a 1997 E420 with M119 motor with 105k miles. The previous owner was using castrol 20W-50, which I think is too thick for MI. Therefore I want to switch to either Rotella T 15W-40 HDEO or Valvoline Maxlife 10W-40. Both are dino oil and cost about the same.

I only drive 6000 miles per year and my commute is less than 4 miles each way. Which oil would be more ideal for my uses??

Use a synthetic, preferrably Mobil 1 0w-40.

It's the 21st century.

I think in this case i would recommend the synthetic as well.... at your mileage you would just have to change it once a year....

i use a lot of different weights...so I wouldn't know...everyone seems to be going towards that 0w-40... i would think 10w-40 would be just fine as well.

Motor oil
 

Rotella T is a fleet oil, formulated to be compatible with either gas or diesel engines. The "T" stands for turbocharger, to prevent coking of the oil in big turbos in large diesels. It seems like a bit of overkill for a gasoline car that gets driven 6,000 miles a year.

Mobil 1 0w40, change it once a year.

I used to put only Mobil 1 0-w-40 in my m119 4.2, till one day i heard rod knock as I was starting the engine (over 40c ambient temperature at the time).

Since then I've been using 20-w-50.

It is the 21st century, which of course is going to hell in a handbasket on many things automotive, including many monuments to cost cutting such as the development and production of engines that absolutely require synthetic oil or they go into the business of producing oil sludge. But you are indeed very fortunate to have one of those great 20th century engines, one of that century's finest, that is unfinicky on the question, a fact which is reflected in MB's recommendations on the subject. I would go with the 15/40.

I tried Mobil 1 synthetic one time. My lifters were noisy as hell! I went back to my tried and true Castrol 20-50, and all was better. Ive been using it for the last 100K religiously, and no problems. I run 10-30 in the winter time, however.

I agree. M1 is the way to go.