Synth or thick mineral?

[fdcg27]

That would be an e30. I had an e36 with the same engine and 20W-50 was among the recommended grades for warmer weather, so the OP is not straying too far off the reservation in using a thicker oil. I know that mine was very happy running Mobil 1 15W-50.
If the OP has seen good results using a 10W-60 or a 20W-60 he may as well just stay with those grades and not use anything thicker.
312K miles is a nice run for a performance 1.8l four cylinder of that era.

 

[Brian123]

It's okay, we don't know what was used but the issue is present & needs to be maintained accordingly. I commend OP for coming to the right place to ask these questions for a possible solution.

I will agree with what you said this time. LOL

 

[Japanese]

But thats way too thin at 5w30

Yes, it's much thiner (lower viscosity) than what you currently use 20W-60, but it may reduce your oil burning by cleaning the engine piston rings' grooves and overall engine internals.

How much 20W-60 oil your engine burns for 8000 km? How often (what interval) do you change your oil?
How much oil your engine burns if you use 5W-40 or 10W40?

 

[SR5]

So do you think i will have an increase in oil consumption if i go to the ticker hp40penrite mineral instead of the motul&castrol synthetics?

No, the thicker mineral oil should likely reduce consumption. Just don’t run it as long.

For example 12,000 km on the synthetic or 8,000 km on the mineral oil.

 

[930.engineering]

.
If a plain BMW M40 (or M42 etc.) 'need' some 25W-70 instead of 5W-30 or
10W-40 this engine actually requires some work or an engine replacement.

Why not check compression and leak test first? Even thicker oil isn't a repair.
.

 

[brinu]

No, the thicker mineral oil should likely reduce consumption. Just don’t run it as long.

For example 12,000 km on the synthetic or 8,000 km on the mineral oil.

The car was bought by my father new in 1992 and it had ran on api SG SH SJ oils for a lot of years so i guess this penrite hpr which is SL wont be worse than those oils..and penrite says that the hpr range is a premium blend

 

[Japanese]

... or 8,000 km on the mineral oil.

I would not recommend to run mineral oil for more than 5000 km, if you want to keep your engine in tact.

Most engines usually burn oil because the owners haven't changed their oil on time. Probably the case with this BMW is the same - they were running mineral or semi synthetic oil and were changing it like it was full synthetic.

 

[UNC006]

This is an old thread, but if you have stuck piston rings, then an extensive B-12 Chemtool piston soak usually cuts oil consumption at least in half. If it’s hard to get B-12, then get lacquer thinner or gun wash with similar ingredients to the SDS (safety data sheet) of B-12. Blend it with 20% high ester based 2 stroke oil of the thinnest viscosity you can find.

Run several tanks of strong gas additive, like Redline Sl-1 for clearing carbon out.

After an extra thorough several rounds of piston soaking, if you’re not going to rebuild the engine, then experiment with the best oil additives available to you that increase compression by restoring the cylinder walls. Then, you could even run less expensive 50 grade oils, have less consumption and better MPG than going up to 70 grade.

Also, instead of oil grade, it’s more important to focus on post shear KV100 and HTHS. Whatever you’re left with after that first 3k miles or 5000km is what’s important. After that, shearing slows dramatically. Also, don’t be scared of an oil that shears significantly more than another, as long as the KV100 and HTHS you end up with is still significantly higher than the oil that shears significantly less.