Sometime in the past year there was a post to a thread here from a guy who switched his diesel MB from synthetic to dino oil and said the engine made much more noise on dino oil. No data was included and I've been unable to locate the original thread, which wasn't about oil (as I recall) anyway.

I decided to run my own test by making two videos of my car idling on dino and on synthetic, then compare the two to see if I could detect any difference in engine sounds. (This is by no means a controlled scientific test.)

Vehicle: 1995 MBZ E300 Diesel
Miles on vehicle/engine: ~200,000
Original (not rebuilt) engine: Yes
Oil used for most of the vehicle's life: Unknown, probably dino
Fuel: Commercial B20 (80% D2, 20% biodiesel)

Synthetic oil used for the test
Chevron Delo-400LE Synthetic 5W-40 (group 3) Rated CJ-4, CI-4, CI-4+, etc. plus. MB228.31. The group 3 synthetics supposedly have good wear properties and wide temperature tolerance but don't have the long-life of a true group 4 synthetic or so GSXR says.

Dino oil used for the test
NAPA Premium Performance Universal Fleet Plus 15W40 (made by Ashland Oil). Rated CJ-4, CI-4, CI-4+, etc. No MB rating. It should be similar to other quality dino-based diesel-rated oils.

Test conditions
For each portion of the test (before recording the video) the car was driven on the streets and highways of Sonoma County, California during a normal morning of running errands (20 to 30 miles). The final leg would have been at 55 mph ending at our driveway. The engine was allowed to idle with the hood up and the climate control off. My iPod Touch recorded 30 seconds of video and sound, hand-holding the iPod a couple of feet in front of the car. Ambient outdoor temperatures were in the mid-80s. The synthetic oil had been used for six months and 5,000 miles while the dino oil was fresh. In that one criterion the test was unequal. I'll repeat the test next winter when the dino oil has 5,000 miles on it.

Here are links to the two videos, "Test 1" and Test 2." I won't tell you now which one is synthetic and which is dino. Personally, I can't tell them apart.

Test 1 Video by Jeremy5848 | Photobucket

Test 2 Video by Jeremy5848 | Photobucket

I don't make any claims for these oils -- they were what I happened to have on hand. My current practice (subject to change without notice) is to change oil and filter at 5,000 mile intervals, using dino for the summer and synthetic in the winter for its cold-flow properties. Driving the '95 E300 10,000 miles/year means I change oil twice a year. My wife's '96 E300, driven only about 5,000 miles/year, uses synthetic year-round, changed annually.

YMMV,
Jeremy

__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970