I must admit that I am disappointed. After much debate and indecision over which oil to use, I finally decided to go with synthetic oil. Cost was never a point, just like wine, if it costs more it must be better, but I do have more valve noise at idle. I debated over going with 15W40 dino or 15W50 synthetic and synthetic won out, but I am not sure if I can handle the additional valve clicking. IS this normal with synthetics, even at the same or higher viscosity? The motor is a 560 with 53,000 miles.

I hope not to start a oil debate, but I am very curious as to the explanation.

Thanks,

BD

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87 560 SL
93 300E 2.8
91 300CE-24

Synthetic oils cannot exacerbate your valve noise problem. As a matter of fact, some synthetic oils (Mobil 1, Valvoline SynPower, Castrol Syntec etc...) have very good cleaning additives which are designed to satisfy ACEA A3/B3 and higher criteria. These additives will help ease the stuck valve lifter problem (less noise
and emission)

Be sure to use diesel-rated oils (CI4) for a diesel car and gasoline
rated oils (SL) for gasoline cars. You can use CI4 oils in gasoline cars too (all CI4 oils also pass SL spec).

Eric

All I can do is tell you my experience: My 300CE had Amsoil 10w30 in it from the previous owner, which is too thin for summer temperatures according to the owners manual. Consequently, I wanted to get the approved 40 weight in there, but couldn't find anything in synthetic in a 40 weight. So I went with Chevron Delo 400 15w-40, figuring it would do for the time-being until I could get my hands on Amsoil 10w-40. After the oil change I was surprised to discover that my valve-train noise was reduced significantly! What does this mean?? Well, I'm not sure. I have nothing against synthetics, but now I am pretty sceptical whether I should put synthetic back in this PARTICULAR car knowing what it sounded like with Amsoil in there - an arguably very high quality synthetic. Delo 400 is also a great oil, so I think I might stick with it FOR THIS CAR and forget about synthetics. Maybe you should do the same with your car.

GregS
'84 300D, 173k
'90 300CE, 163k

CI4 spec oils (for diesels) like Chevron Delo 400 have a higher detergent content so over time they would clean up sticky lifters. Maybe that's what happens. I use it in my 72 4.5 and it has cleaned it up the engine very nicely. The first time I put it in it got black immediately so I think it picked up a lot of gum and soot quickly. Mobil 1 is probably a more effective lubricant so it's a tradeoff.

The hydraulic valve lifters in my recently purchased 190E 2.3 are intermittently noisy during warm-up but OK hot. The engine oil in the car at the time of purchase was a Mobil 10W-40 semi-synthetic. Recently I changed the oil and filter using a Shell 15W-50 semi-synthetic, a viscosity range that suits our climate of cool to mild winters with warm to hot summers, and consistent with the requirements of such a motor at 215,000km. The lifters have actually been noisier since the oil change. Obviously in this case, the lighter oil is more suitable for the problem with the lifters. This would also tend to explain the lifter noise during warm-up (when the oil is thicker) and the lack of noise when the oil thins when hot. As to the explanation of what actually occurs with the lifters, I cannot answer that. Obviously the real fix is to replace the lifters, a job I am planning in the not-too-distant future.

__________________
107.023: 350SLC, 3-speed auto, icon gold, parchment MBtex (sold 2012 after 29 years ownership).
107.026: 500SLC, 4-speed auto, thistle green, green velour.
124.090: 300TE, 4-speed auto, arctic white, cream-beige MBtex.
201.028: 190E 2.3 Sportline, 5-speed manual, arctic white, blue leather.
201.028: 190E 2.3, 4-speed auto, blue-black, grey MBtex.
201.034: 190E 2.3-16, 5-speed manual, blue-black, black leather.

For the record, my situation has nothing to do with the "dirty engine being cleaned by Delo 400s cleaning agents" scenario. It had Amsoil in it for many thousands of miles and was spotlessly clean to begin with. The reduction in valvetrain noise occurred immediately after changing the oil.

GregS

Thanks for the input. I believe that I will go in an check the hydraulic compensators and adjustment with the go-no gauge and also check for bleed down of the unit and the ability to hold pressure. If everything checks out, I am going to go back to the 15w40 dino.

I thought that any oil at a given viscosity rating, like 15W50 should be the same. I am just surprised that the valves are noisier with the synthetic. The inside of my valve covers and head are as clean as the day it was new. The additional valve noise was immediately noticeable on startup after the oil change. It is nosier warm vs. cold. Does the synthetic form a thinner film of oil? One explanation could be that viscosity is a measure of flow and does not have an effect on how thin the film of oil is or the body of the oil. I am guessing.

BD

__________________
87 560 SL
93 300E 2.8
91 300CE-24