Lubri-Moly makes good oils. In your climate, you might also consider 15W-40. Although you don't drive it in Winter, I'll bet there's some 10 deg C (50 degree Farenheit) mornings in Spring and Fall.
It's important to get oil flowing quickly in the moments after start-up.

 

It will be OK, at least there's something in it. Change it now I would.

For level, the convention I always followed was operating temperature, switch off the motor, wait 10 minutes, then check.

 

I've heard that some folks are running Shell Rotella 15W-40. Although marketed as diesel engine oil, it's also rated SM good for older petrol engines.
Here it is at Walmart Canada:

Verify Your Identity

 

I was skeptical when i saw that it’s diesel oil. A few others recommended a Mobil 1 commercial diesel oil but I feel I rather not make that switch now not knowing what the car has been running on all these years. Is the Castrol GTX a safe bet? It’s rated as

• API SN, GF-5

Should I do an engine flush prior to oil change? What can I use for engine flush / injector flush / fuel system flush that’s safe for these cars?
Thanks all

 

I was skeptical when i saw that it’s diesel oil. A few others recommended a Mobil 1 commercial diesel oil but I feel I rather not make that switch now not knowing what the car has been running on all these years. Is the Castrol GTX a safe bet? It’s rated as

• API SN, GF-5

Should I do an engine flush prior to oil change? What can I use for engine flush / injector flush / fuel system flush that’s safe for these cars?
Thanks all

Castrol GTX is excellent. Used it for years in 20w-50 in my 67 230SL, but recently switched to Valvoline VR1 Racing oil that has Zinc for solid lifters (like the m110 engine has). But I live in year-round HOT Florida where I never start my roadster below 20 deg.Celsius and typically drive in 30-35deg.+ Cel. If you can get Castrol GTX in 15W-40.... Bingo!

However, If I lived in a Northern climate like Canada, IMHO 20W-50 is too thick for starts at 10 deg. Cel. or below as it won't flow as quickly during the most critical first seconds after startup. Having the correct weight is perhaps more important than which 'brand' of oil. Whether it say's diesel or not, look at the gasoline rating on the oil; if it's Service rating is SL, SM or SN it's better lubrication than what was available 40 years ago. -JMO

Having driven several Mercedes well past 500,000km without any major engine work; I agree with ianrandom that frequent changes with good quality filter is best medicine for motor health.

 

I like to flush with engine flush by Wurth or Millers. Nothing too harsh.

Another thing I did with my W126 was do a few repeat oil changes with cheap oil, only a couple hundred miles between them. Then genuine filter and classic friendly oil with ZDDP in it to an appropriate amount.

I've heard that Shell Rotella thing too. I wouldn't hesitate to use a diesel oil if it was me.

Wurth also do a good injection system cleaner. I started using them because the cleaner sold by MB is made by Wurth.
There's loads on the market though, over the pond I often see reference to Techron and things like Seafoam. Endless opinions out there on all this though, so if you research it, allow plenty of time 😁

 

I forgot to ask if your 280SE has a catalytic converter(s)? If so equipped, that's a consideration for NOT using high ZDDP oils recommended for older 'classic' cars with tappets and solid lifters. The zinc/phosphorous zddp additives can shorten the life of cats.

However, there are still some ways to get 15W-40 oil, with additives for solid lifters, that meet high SM or SN Service requirements for gasoline engines. Like Shell Rotella T6.

Here's a good summary from Wikipedia regarding Shell Rotella offerings:

Shell Rotella - Wikipedia

en.wikipedia.org

 

My car is a German import and I am not sure if it has CATS or not but I do think that it does. See images.
I just want to get a oil that's good all year round in case I decide to take it out in near 0 temps which I likely will not unless the weather is sunny and tempting as it can be sometimes in december. From all the reading I have done, it sounds like 10W40 or 15W40 are the way to go for Canadian weather.

 

I can't tell, but if it has cats then unfortunately yes, ZDDP is not so recommended. I believe that's why modern oils don't have it much as a feature now.

 

Well....If you can't find a 15-40 full syn with high Service Rating (SM or SN) for gasoline engines that is suitable for cats (I believe the newest Rotella T-6 would do it if you could find it in 15W-40); I think this one would work for you..... LIQUI MOLY MOS2 ANTIFRICTION SAE 10W-40 1 L | Walmart Canada

In fact it might be fine in your other 1980's Benz's as well. It has the temperature viscosity range to handle both cold and warm Canadian weather, and it has the anti-friction additive MOS2. It's not full-synthetic, but perhaps a better transition if the car has had only conventional oil, and it's more affordable for flushing it frequently. I think it's also available in semi-syn or full-syn but I didn't see it at Walmart. My 2cents. Just do it!

P.S. The Semi-Syn version IS available from FCP

10W40 MoS2 Anti-Friction Engine Oil (5 Liter) - Liqui Moly LM2043

10W40 MoS2 Anti-Friction Engine Oil (5 Liter) - Liqui Moly LM2043

www.fcpeuro.com

 

Thank you all for the replies. I have gone with the 10W40 Liqui Moly. Wondering if I should switch both my W126s 87 420/560 over to this oil as well? Currently they are running on 5W40 full synthetic

 

If you get the semi-syn version, yes I would run the same oil in all three. Good oil from Germany. Makes life simple.

 

The version I got was dark gray oil. The guy changing it was quite shocked because he’s been doing this 20+ years and never seen new oil look like that! How are you supposed to know when the oil has aged.. will it go from gray to black?

 

.

Yeah....Lubri-Moly comes with additives that are grey-ish. But they do an excellent job of lubricating.
I'm used to diesel engines where even fresh oil turns dark after the first few kilometers.
Just keep track of mileage to determine when it's oil change time. But if the color bothers you....guess you'll have to go with a different brand.