Oil to M30B34

[SushieateR]

Hi,

I know "what oil to" topic is not easy, but I have to buy oil to my 735iA which will be transported to me next week. Not sure which one to pick.
Which oil you guys use? Correct me if I am wrong, but I think 15w40 is recommended? Full synthetic?
Anything from Motul maybe? I am using 5w40 Motul in VAG 1.8T and I am very content with it.

[Jay535is]

Going into the winter months a lighter oil like a 15-40 is great.
In the summer months keep it heavier wtih a 20-50.
A 5-40 is way too light, you'll hear the difference with a proper viscosity oil.

[8991XJ]

These motors want thick oil.

Here is what the manual specifies.
20W-50 15°F to 122°F (-10 to 50°C)
15W-50 -4°F to 105°F (-20 to 40°C)
15W-40 -4°F to 85°F (-20 to 30°C)
10W-50 -20°F to 68°F (-30 to 20°C)
10W-40 -20°F to 50°F (-30 to 10°C)
10W-30 -20°F to 40°F (-30 to 5°C)
5W-30 -40°F to 22°F (-40 to -5°C)
5W-20 -40°F to 15°F (-40 to -10°C)
SAE 20 (-20 to 10) °C
SAE 30 (0 to 30) °C
SAE 40 (20 to 50) °C

[SushieateR]

Thank you for the response.

I have also found some information on bigcoupe.con about Oil for M30 Engines.

But the thing is, finding proper oil is not easy it seems.
All 10W50, 15W50 or 20W50 synthetic oils I found (Liqui Moly, Motul..) are theoretically for motorbikes.

Or for sport like Motul 300V or 10W60 Valvoline VR1. Quite sure these will not match to e23

Motul has series of oils for old cars (Classic Oil 2100 15W50) semi synthetic. Maybe this one will do?

Maybe VALVOLINE MaxLife 15W40 or Motul 6100 Synergie+ 10W40 also semi synthetic.

[8991XJ]

I know that synthetic is the better oil. But I don't need to use that in my rides as I can change oil regularly. For this reason, I don't insist on using syn.

I looked at the Motul and that stuff designed for cars from 1970 to 2000 has the key ingredient we have been looking for in the last decade, zddp, a high pressure additive to keep the valvetrain in good shape. Most oils in the US have had this additive removed to a large extent for pollution control (it will damage a catalytic converter).

I would say the Motul is a fine oil for these cars. It seems to be available in the grades you need, the top 3 or 4 in that list up there.

[Jay535is]

There is no need for full or even semi synthetic oils.
These motors were designed and built with much larger tolerances than modern engines.
Any standard or diesel oil of the proper viscosity will do.
I like 15-40 diesel oil, high levels of ZDDP.

[SushieateR]

I see, this helped a lot - thank you. Will probably go with this Motul 2100.

Forgot to mention Motul 4100 15W50. Theoretically designed for older engines with high mileage. Semi-synthetic. Does it have enough ZDDP? Do you think it will also be ok? 1/2 price of 2100

[Jay535is]

You are way overthinking this.

[SushieateR]

Dad told me the same.. But got told before to be careful as "modern" synthetic oil can wash such engine too much and finally ruin it so I'm playing safe

[Jay535is]

The big difference is most modern cars use oil that is so thin its useless on our old motors.

[8991XJ]

The big difference is most modern cars use oil that is so thin its useless on our old motors.

If you look at the modern, well not quite, that would be a 0W-20 or some such watery stuff in the list above one would realize that an M30 motor running the thinnest oil listed, the 5W-20 would need to be used on Antarctica or well above the Arctic Circle as the highest ambient temp for this oil would be 15°F or -10°C. damn cold.

[XAlt]

There's no issue in running a quality 5w40, they all flow the same when hot.

Something like 0W16 is another story.

[SushieateR]

Bought Motul 15W50 eventually

[Thradya]

I've read somewhere that the only reason not to go thinner is oil pressure - which makes sense to me. So run the thinnest that your engine can tolerate. Mine doesn't tolerate anything less than 10W60 - so that's what I'm running.

[Jay535is]

And you won't know what it will 'tolerate' until it is too late.

[8991XJ]

Been rocking an OP gauge in an M30 since 86. Tells me the answers I need. Car never had anything but Castrol 20W-50 until a few years ago when I was forced to throw in some 7½W-35, a mix of two weights, used to get me home from about 3 hours away.

One interesting thing is that motor with old tired 20W-50 in it will have low oil pressure at hot idle but with good fresh oil after the change, hotter day, same warm up it had proper oil pressure at idle.

I don't want low oil pressure.

[Furreals]

I use kendall 20-50. Recommended by someone a long time ago due to having properties good for the M30/ older motors.