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5W50 or 10W50 oil ??

there is a little pressure vacuum when you take the oil cap off but it does not smoke. the idle seems to drop a little but am told that is normal

will try the different oil route first and see if that makes a difference

then maybe look at the AOS change route.
 
I'm using 10/50 millers.
What I've noticed is when cold the engine idles lower to the point where you can feel it in the car.
It also turns over slower when starting from cold and since using it my starter let's a screech as the engine starts. (Don't sound nice)
T
At £120 it can say in there for the time being but on the next service think I'll be going back to 5/40.

On the plus side oil pressure is up at around 2bar at idle and just over 4 at 70mph
Engine sounds and feels soother to.
 
Your starter motor schreech has nothing to do with the oil. It's clutch dust on the starter shaft and just needs cleaning.
 
captain caveman said:
Anoyingly it's only done it's since I had the oil and ims changed a couple of weeks ago.

Looks like whoever did the job has blown the clutch dust from your bell housing area into the starter motor.
 
Just in case anyone was unsure. 0W-40 is not thinner when its cold than hot. The W rating and the summer rating are two separate and completely different measurements.

The W rating is based on cold cranking viscosity (and is a maximum spec not a minimum) and pumpability.

I have run mine on 0W-40 before. On a cold start it's still comfortably above 5 bar oil pressure at idle. A 10W would be even higher (unless it's up against the pump PRV) Therefore yes it is providing perfectly adequate wear protection. It will also circulate round the engine quicker than a 10W.

Having said all that, the rating indicates that a 10W is good for like -15deg C, a 5W is good for like -25deg C, and a 0W is good down to -35 . So 10W are absolutely fine for our climate, but 0W won't be doing harm.
 
That's very useful info thanks

So what about the 40 and 50 numbers? Does the 50 provide more protection when the engine is at higher temps and will maintain viscosity and not start to break down like a 40 would ?
 
NLW73 said:
That's very useful info thanks

So what about the 40 and 50 numbers? Does the 50 provide more protection when the engine is at higher temps and will maintain viscosity and not start to break down like a 40 would ?

50 is just thicker at a hot temp than a 40, I cant remember the temp they test at.

The quality of the oil determines how long it lasts before shearing down and getting thinner.

e.g. a synthetic base oil will resist shearing longer than mineral.

This is why manufacturers like synthetic oils, means the car can go for longer between services.

They also have more additives to keep dirt in suspension longer - bear in mind longer intervals means dirty oil is getting dirtier for longer and the dirt is pumped around your engine.....

Esther base oil is used in race and track applications as its the toughest, resists shearing at sustained higher temps.
 
thanks for that.

so if I am dropping the oil every year maybe twice a year then I don't have to worry too much about long life and the oil getting dirty and rotten and doing too much damage
 
I found the vacuum sucking through the oil filler cap not to be a reliable indicator of AOS condition when I suspected mine was going. The real indicator that something was wrong was oil in the inlet manifold. The way to find out is to take off the throttle body and stick your hand in there and prod around in the low points, looking for pools of oil.

It's well worth checking - I left mine until it failed completely, and when it went it sucked several litres of oil into the inlet manifold and filled up two cylinders, instantly stopping the engine, which would have been scrap had it not been for the fact it was only at idle. After I replaced the AOS, I had to turn the engine over with no plugs in to pump out the oil, and then once it was running again, I drove around like a Red Arrow for 10 miles whilst the oil was burned out of the exhaust. I did the AOS replacement myself with the engine in the car, and it was by far the worst job I've ever taken on. If I ever need it doing again then I'll be paying an indie to do it.
 
NLW73 said:
thanks for that.

so if I am dropping the oil every year maybe twice a year then I don't have to worry too much about long life and the oil getting dirty and rotten and doing too much damage

Well the manufacturers and oil companies will say the dirt is doing no harm in suspension and actually its all fine.

But then they do design cars based on a life and a cost - theres no point in having somethings last far longer than other things. I rather suspect most of the time that life is 150k miles and 15 years.

We want our 911s to last much longer so do whatever we can to extend the life of things.

So yes much more frequent oil changes may well extend the life of some things, but other critical components may reach their life meaning engine replacement or rebuild is necessary anyway, making the extra oil changes futile (IMS bearing anyone?).

Do whatever makes you happy.
 
Martin996RSR said:
I found the vacuum sucking through the oil filler cap not to be a reliable indicator of AOS condition when I suspected mine was going. The real indicator that something was wrong was oil in the inlet manifold. The way to find out is to take off the throttle body and stick your hand in there and prod around in the low points, looking for pools of oil.

It's well worth checking - I left mine until it failed completely, and when it went it sucked several litres of oil into the inlet manifold and filled up two cylinders, instantly stopping the engine, which would have been scrap had it not been for the fact it was only at idle. After I replaced the AOS, I had to turn the engine over with no plugs in to pump out the oil, and then once it was running again, I drove around like a Red Arrow for 10 miles whilst the oil was burned out of the exhaust. I did the AOS replacement myself with the engine in the car, and it was by far the worst job I've ever taken on. If I ever need it doing again then I'll be paying an indie to do it.

Yes my car was running fine, but I did notice a film of oil in the inlet and around the inlet hose joins that must have come from somewhere.

So when I dropped my gearbox I changed my AOS while I had access. Indeed the old AOS had oil in every port (except coolant ports) meaning some was letting by, and it might well have failed sometime.

However if I hadn't dropped the gearbox I wouldn't have bothered. I wish I had just dropped the engine, it was still difficult to manhandle the AOS into position even with the gearbox out. At this age there are other jobs I could have done with engine out, I do now wish I had just dropped the lot.
 
wasz said:
NLW73 said:
That's very useful info thanks

So what about the 40 and 50 numbers? Does the 50 provide more protection when the engine is at higher temps and will maintain viscosity and not start to break down like a 40 would ?

50 is just thicker at a hot temp than a 40, I cant remember the temp they test at.

The quality of the oil determines how long it lasts before shearing down and getting thinner.

e.g. a synthetic base oil will resist shearing longer than mineral.

This is why manufacturers like synthetic oils, means the car can go for longer between services.

They also have more additives to keep dirt in suspension longer - bear in mind longer intervals means dirty oil is getting dirtier for longer and the dirt is pumped around your engine.....

Esther base oil is used in race and track applications as its the toughest, resists shearing at sustained higher temps.


The summer number is based on the kinematic viscosity of the oil at 100 deg C. There is also a minimum shear rate for the oil in a simulated bearing test run at 150 deg C but basically the kinematic viscosity defines the grade.

A 50 is somewhat thicker than a 40 at high temps which gives a little more protection especially for an engine with a high number of miles or one that gets driven hard and reaches high temps. 40 grade is 12.5 to 16.2 cSt, 50 grade is 16.3 to 21.8 cSt. So they can be write close or a fair way apart depending on where each respective oil sits within their range. However to put these numbers in context, at 40 deg C, a 0w-40 oil such as Mobil 1 is around 75 ish cSt

I doubt you can even get porsche A40 spec oil that isn't fully synthetic. You definitely want to use a fully synth whatever grade you use.
 
Thanks for posting Phil bit of an eye opener :thumb:
 

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