Navaros911

Last week I was sitting in very slow moving traffic with 110+ degrees F outside... The car was doing fine on approach with the temp needle sitting just under the halfway point on the gauge.

As time went by the temp needle started creeping higher and higher... when it hit the 3/4 - or maybe just under it - point the oil pressure warning light went on.

This happened only when sitting idle with less than 1000 rpms... actually the car in that traffic was struggling not to stall and hit some 550rpm spots before coming back up to 800... at that time the oil pressure would drop to 0.6 bar maybe (half way between the bottom and one up from the bottom) and the oil warning would go on. Pushing the accelerator to get the rpms up to about 1500 would make it go away, but when I let go the same would happen again.

Needless to say I got out of the traffic ASAP and headed the other direction at 60mph and all was fine after 10 mins.

Now my question is: should I consider other oil since it is always HOT in this country?

Currently she is running on 0W40 Mobil 1... should I consider 20W50 or 10W50 or so?

Indycam

Where are you ?
Does it ever freeze where you are ?

evoderby

As a rule of thumb engines have a (minimal) requirement of 10psi / 0.7 Bar of oil pressure per 1000 rpm. This means at 800 rpm you need at least 0.55 Bar which is a bit below the 0.6 Bar you saw when the warning light came on.

Now the good news is this means the warning light does really serve a purpose and warns you in advance of oil pressure related engine damage, at least at RPM's around idle. Should you rev the engine to say 3500 rpm to bring up oil pressure to say 1.5 Bar the warning light does go out since you're now running above 0.6 Bar, but there's too little pressure for those revs (2.5 Bar is required).

Therefore be really careful with reving engines to 'restore' oil pressure.

The question in your case is now what to do? Is your problem oil or mechanical?

The 0W40 you're running is meant to flow really well when the oil is cold on startup to reach the area's that need lubrication as quickly as possible to minimize startup wear and tear.

Over time your oil degrades and doesn't behave like the 0W40 it says on the box. Instead what once was grade 40 at higher temperatures when new in the box has now become 20 due to load, dilution etc. Oil analysis shows this time and time again, making this a very real world example.

Some oils degrade very rapidly, others are longer lasting.....all do over time and the effect is always: lower oil pressure! *

* not taking into account pressures above the activation pressure of the oil pressure relief valve.

This why in endurance racing 10W60 type oils are often used that even when suffering from degration still offer ample protection and pressure even under the highest of temperatures. (A 0W30 will give a bit more power due to lower oil drag for applications like a 25 minute race followed by an oil change).

Given the fact that you live in a warm climate I would recommend you try a 10W60 full synthetic**, as I am sure this will provide positive results on your oil pressure.

What it won't do however is restore worn bearings that are a main mechanical cause for low oil pressure. If after switching to 10W60 your idle pressure remains below around 1.25-1.5 Bar you know you're probably in for an engine rebuild. May the force be with you!;-)

**BMW Europe strictly prescribes Castrol TWS 10W60 for the M3 M5 M6 Z8 (now renamed castrol Edge 10W60 - NOT THE OVER THE COUNTER Edge SPORT 10W60!!) . This imo is also a very good oil for the 964 as it has sufficiently high ZDDP levels to provide high shear resistancy coupled to daily use high mileage life expectancy required from OEM's.

Navaros911

Thanks... this is good advice.

I live in Bahrain (in the middle east) and it gets darn hot in the desert here - and never freezes. Normally the car does fine in terms of oil pressure. It stays around 1bar at idle and climbs 1.3 bar per 1000 rpms with about 4 bar at 3k rpm. So the engine seems fine to me. It had a top end rebuild once, but has only 75k miles on it. I know the oils they use here is the 0W40 Mobil 1 stuff. I was leaning to the Castrol RS 10w60 for a while (now your Castrol Edge).

Guess I will be calling Castrol tomorrow...

Navaros911

Why not the Edge Sport oil?

evoderby

Castrol Edge 10W60 has an API SJ specification

Castrol Edge Sport 10W60 has API SL specification

One of the main differences between those API specs is the amount of ZDDP (zinc and phosphorus anti wear additives) that is allowed in the oil. While these are great for protecting the engine under extreme conditions they impose a negative effect on emissions / catalyst life. For this reason over the past decade ZDDP levels have been greatly and continuously reduced in mainstream engine oils (the higher up the API spec in the alphabet, the lower ZDDP levels are, in this instance J vs. L).

BMW has specifically chosen for the high ZDDP spec oil for the high revving >100Bhp per liter M engines to provide the necessary protection. This spec also suits the 964 best with its mechanical valve train, although some sources suggest that as long as the oil meets ACEA A3/B3 specs such as the lower ZDDP spec Castrol Edge SPORT the oil is suitable enough for 964's.

I care more about engine life than catalyst life, I've recommended the (non-sport) Edge accordingly.

Good luck!

Navaros911

This is great info, but I'm slightly confused...

ZDDP is good for protection, so we want a lot of it: right?
That's why BMW chose the high ZDDP (Cstrol Edge 10W60 with an API SJ spec), which is higher up the alphabet - to protect the M series engines.

Is this a typo then:

I have a 964 with the 150 (I believe that is the option number) option: No Cats! So I'm not worried about ruining them

The bottom line is: Go with the Edge 10W60.

I am not sure if I can get it that easily... I've seen the sport all over the place, but the straight Edge at 10W60 seems harder to get a hold of. I will need to check with the distributor.

evoderby

Indeed ZDDP is good and we want lots of it. The J comes sooner in the alphabet than the L, therefore no typo's in my message.....J (Edge) has more ZDDP than L (Edge Sport).

Option 150 sounds like a great option BTW! ;-)

breale01

Do you know the exact ZDDP number in the Edge J? Wondering how it compares to M1 15W50 SL/SM's 1200.

evoderby

1294 ppm (castrol TWS before it was rebranded Edge)

wellcraft290

so if i switch to castrol is the weights ect big difference from mobil 1 15w-50?

Navaros911

I see... I was thinking A has a higher ranking than Z... but you look at it the other way around

Thanks for the info... it is definitely a wake-up that I need to change oil type here.

Navaros911

Just as an update to the thread: I've been running Brad Penn 20w50 for a while now and have no low pressure problems anymore.

In the winter I mix it with 0w30 to blend it to a 5w40 ish oil.

Working fine this far.

KNS

Brad Penn is a great choice for the climate you are in! That's what I run here in Phoenix, Arizona (pretty hot here as well).

PNine64

I run BP as well up here in Ohio. Ordering from LN Engineering gets it to me the next day (which is awesome because I'm terrible at ordering things in time for the weekend). Unfortunately, I don't drive it in the winter so I don't have to even think about whether the original blend is sufficient for cold weather.