20W50: all season oil?
 

Am considering replacing standard 15W40 oil with 20W50 on my 120K W124 to suppress oil consumption.
Is 20W50, however, an all season oil? (moderate climate here...)

Cheers!

Depends on where you live...
 

My 560SEL manual says that 20W-50 is suitable for temps above 0 degrees C. So if you live in southern Europe, you might be OK.

20W50 is good for a warm-hot "Mediterranean" climate.Definitely do not use 20w50 if you park your car outside. Once you park your car outside the engine is really cold thus impeding cold startup oil flow. You dont mention if you have a 300E but MB used 20W50 since day 1 even in cold climates.

Another way to determine what viscosity is best for you is monitoring your oil pressure gauge. If you see it goes down to 1 after a couple of minutes then use a heavier weight. If you mostly take the car on freeways use 20W50 but if it is a short trip car, use less viscosity. The m103 has an iron block thus it is hotter than your standars Al engine, so dont use a 5w20 or anything silly like that.

20W-50 was the most popular weight of oil 20 years ago!! But todays engines are built so much tighter that you need a lighter oil. Also the most wear that engines have happens durning warm-up so if you stay with a lighter oil then the engine will last longer.
IF you want a good that is rated for 100+F outside temps then use a 5W-50 OR 10W-50.

Thanks all,
Temps here range from 15F to 85F max.
Engine uses one quart per 1000m, and uses standard 15W40 oil (Castrol). Cause of consumption is unclear: no blue smoke, dry plugs, no leakage, max oil pressure. The idea behind 20W50 is that this thicker oil is better contained inside the oil system of a 120K mileage engine, compared to the thinner 15W40.
However, if 20W50 is for sunshine states only, its of no use to me in view of the climate. It will be clear to you, that I don't understand the multigrade system...

What type of (mineral) oil is thicker than 15W40, and has the multigrade viscosity that fits the temp range where I live (The Netherlands)?

Cheers!