I want to run synthetic oil in my 400E. IS this a good idea? If I do, it would be redline. What grade should I get. Does the engine recommend against using synthetic?

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93 300D 2.5 Turbo, Black/Palomino 273K
09 E350 Black/Black 41K

do a search for "synthetic oil" and read away.

there are many many threads discussing this very topic.

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'94 W124.036 249/040 leder; 8.25x17 EvoIIs
'93 W124.036 199/040 leder; 8.25x17 EvoIIs, up in flames...LITERALLY!
'93 W124.036 481/040 leder; euro delivery; 8.25x17 EvoIIs
'88 R107.048 441/409 leder; Euro lights
'87 W201.034 199/040 leder; Euro lights; EvoII brakes; 8x16 EvoIs - soon: 500E rear brakes
'70 R113.044 050/526; factory alloys; Euro lights

I agree -- do a search and you'll see a ton of info and opinions.

Personally I think there are several good reasons for using synthetic in the 119 engine. These engines, at least when in the W124 chassis, tend to run on the hot side, and thus the extra protection of a synthetic may give a little insurance. Also, the timing chains on these engines are very long. Chains are said to "stretch" over time, but what really happens is each pivot point on the chain wears just a little, and the cumulative wear across the whole chain causes the chain to lengthen. I have convinced myself that using synthetic oil MAY reduce that wear and stretch and again may give a bit of added insurance.

I use Mobil 1 15W-50 year round.

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Steve
'93 400E

so long as the oil is changed frequently and regularly, synth or not, you ought to be fine. even with the hotter M119. However, if you drive the car hard during the interval, then yes, you would benefit from going to a synth...or, you could just change more frequently.

synth is used in racing because of the extreme stresses that are placed on the engines. 18,000 rpm for a v-10 in F1 but they don't have the opportunity to change the oil at a pit stop, so they need something that won't break down.

As a "regular" driver, i, personally, can't justify spending 2x as much for oil i'm going to drain out at 3,000 mi anyways. Dino oil works fine up to that point and is cheaper

just my position on the whole issue.

if you prefer synth, by all means, load 'er up

__________________
'94 W124.036 249/040 leder; 8.25x17 EvoIIs
'93 W124.036 199/040 leder; 8.25x17 EvoIIs, up in flames...LITERALLY!
'93 W124.036 481/040 leder; euro delivery; 8.25x17 EvoIIs
'88 R107.048 441/409 leder; Euro lights
'87 W201.034 199/040 leder; Euro lights; EvoII brakes; 8x16 EvoIs - soon: 500E rear brakes
'70 R113.044 050/526; factory alloys; Euro lights

I don't know of any engine that can not take syn. As for which weight, use something like 5W-40 or 0W-40. Since you plan on using Redline, I don't know what weights they have. 0W-40 is the factory fill for new Mercedes.

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1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member

Please do a search here (you'll get everything from scientific analysis to links to oil websites and testimonys) and stick to the change intervals in your owners manual and you won't go wrong. Make your own informed decision and do what you feel is comfortable to you for oil grade and type. One person says one thing another says the opposite, its like a Consumer Affairs nightmare An answer to this question is loaded with opinions, truths, lies, heresay, etc.

One thing does remain true through it all and that is engine oil is the life blood of your engine, take that how ever you want Good luck