engine and drivetrain Oil Weight

[brianstj]

Just looking at a thread asking about what brand oil everyone uses, and I noticed that almost everyone is running Xw50. Why such high viscosity? I have a fresh rebuild with a couple thousand miles. I've been running 10w40 since I put it together. In the warmest weather I have driven in the oil pressure has not gone below 55 PSI at cruise and 25-30 at idle. At start up (especially on cooler mornings) the oil pressure can easily sit at the 80 PSI mark where the pressure relief valve starts dumping.

So why is everyone running this thick oil?

Another thing I found interesting is that I just bought a new Toyota, and it is only supposed to run 0w20 for ALL temperatures. So what is different about modern engines that allows for such light weight oil?

[nbristow01]

Its what BMW recommends and it is what I use. No need to question, just do it

[c.d.iesel]

(nt)

[c.d.iesel]

THINGS HAVE CHANGED A LITTLE

in the 50 years since this motor was designed

go by the Owner's handbook

[tjones02]

Nothing wrong with using 10W40 on a known fresh motor, just not what the majority prefer. It's simply what BMW recommended for the bearing and cylinder tollerances of the M10 motor.

I can see using 10w40, just wouldn't recommend anything lighter unless you are predominately in a very cold climate.

The recent thread referred to...

http://www.bmw2002faq.com/component/option,com_forum/Itemid,50/page,viewtopic/t,341302/

Like I said there, I like and use 20W50..... just as my father does in the Tii he bought new that went over 220K on the original motor without issues.

[jimk]

Seems recently oil questions are coming fast and furious.

SAE 50 was the order of the day 35 years ago when oil had poor temperature oxidation resistance. Many use it because "bigger is better" syndrome and also just because the other guy uses it (sort of a blind leading the blind problem). I've never used anything heavier than 10W-40 and only use a sunthetic for the last 32 years because of the high temperature capabilities. Actual lab analysis of the oil shows no detrimental characteristics after 4 times the 4k change interval in the BMW owners manual. I hold 60psig pressure with hours of constant 75mph cross country cruise trips (just got back from a 1700 mi trip).

You are right, a 20W-50 oil is just a thick fuel consumming, heat building churning oil. Actually rod and main bearings can run hotter with it because of the lack of cooling oil flow. My sump runs 185F on those constant speed freeway runs. You are doing right.

[jimk]

Seems recently oil questions are coming fast and furious.

SAE 50 was the order of the day 35 years ago when oil had poor temperature oxidation resistance. Many use it because "bigger is better" syndrome and also just because the other guy uses it (sort of a blind leading the blind problem). I've never used anything heavier than 10W-40 and only use a sunthetic for the last 32 years because of the high temperature capabilities. Actual lab analysis of the oil shows no detrimental characteristics after 4 times the 4k change interval in the BMW owners manual. I hold 60psig pressure with hours of constant 75mph cross country cruise trips (just got back from a 1700 mi trip).

You are right, it's just a thick fuel consumming, heat building churning oil. Actually rod and main bearings can run hotter with it because of the lack of cooling oil flow. I don't believe bearing clearances are any more tight with todays engines than they were when the M10 came out and today's engines don't call for the heavy oil. If so, I'd like to see the numbers. My sump runs 185F on those constant speed freeway runs. You are doing right.

[TEAEYE]

CD had me laughing over his 50 years comment,

so just for S& Giggles I unearthed an original in German,

Betriebsanleitung 2000 TILUX, dated Nov. 1967.

In which and at that time the only suggestion on motor oil is as follows.....

Marked HD oil for Ottomotor, SAE 30 over 0 degrees Celsius........under 0 degrees Celsius use SAE 10W 30

And that is it, short and sweet! L.o.L!

It does however suggest that during summer months to change the motor oil at 6000KM, during winter months every 3000KM.

Jon

[Guest Anonymous]

Its what BMW recommends and it is what I use. No need to question, just do it

BMW also recommends using 165mm wide tires too.