The oils viscosity is much thicker when cold. It will rob some power. Although I am not sure if you loss is excessive or not. If you know of another member locally with the same basic car. A direct comparison might be helpful. Thats before starting to check other things out.

What you quote sounds more like a 240d on dino base oil. When their engines are cold you have to almost live it to understand. I always idle at least a couple of minutes before taking off cold.It does help on those. With a short one mile comute and to enable easier starting in cooler weather mind the possible oil drag issue. I might put synthetic oil in your car. It does make quite a difference.

Since you brought up possible temperature related issues. If the turbo engine is hot and you have just travelled a fair distance at speed. It is felt by some mechanics the engine will last longer if you let it idle for a minute to equalise temperatures before shutting down.

This also keeps colder oil flowing to the turbo bearings until it has had time to slow down. Otherwise when you shut down the turbo may still be spinning at 150 thousand revolutions and there is a lot of residual heat absorbed into the bearing and seal area if you stop the oil flow. The remaining oil may start to carbonise a little even.

Although the low designed operating temperature of these blocks in general would not be prone to form really excessive hot spots. I have always wondered why mercedes ran their diesel engines at lower than optimum operating temperatures. Just to cater to customers that treated their cars like gas ones perhaps?

I know operating at 160F or 80C hurts fuel milage and makes the wear component so much higher normally. So high these engines do not see 500k without requiring a rebuild usually.

From the mercedes companies perspective they probably felt the original owners would not keep their cars long enough to really matter. I also tend to agree if that was their rational.. Someday I will attempt to find out exactly why they did this. If someone else knows it would be helpful.

If you are in a situation that you can put a timer on the block heater in cooler weather even one hour activation before driving off should make quite an improvement.

Engine wear is reduced and fuel consumption will be lower on a short commute. Starter, battery,and alternator wear is reduced etc etc. For the slight cost of the hour pre warm electrically I really think it would be cost effective.

Your description otherwise is what I would define a rough or heavy duty cycle basically. So also take the car for a run once a week to boil off the condensation that may accumulate. I have seen cars used steadily in this fashion have at least a quart of water accumulated in the base oil otherwise.