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Oil Pressures with New Oil

scam75

scam75

Well-known member
Well I had promised myself that I would start running a fully synthetic oil after my recent engine re-build. The car got a 10/40 semi after the re-build to run it in and now I've covered over 1k miles I decided to do a change and put in a full synthetic. I got a good deal on some Lucas 10w-60 full synthetic and what a difference it has made. Hot idle is now just over 4 bar whereas before it was just under 3 bar and I would say that oil pressure has probably lifted by one bar across the range. Also my noisy tappet has almost completely disappeared as well so it would seem that the old girl is more than happy with this thicker oil.

I assume it's perfectly normal to see these changes in pressures because of the difference in oil quality and grades?

Stuart
 
Here we go again... but seeing as your asking, I'd say its normal yes, but high oil pressure isn't necessarily an indication of good oil flow, a thinker oil will increase pressure as its harder to pump around the engine, you can still have high pressure and poor flow, I'm not saying you have poor flow but its just something to bear in mind. I still think 10w60 is pretty thick for anything other than a full on race car, but now you have it just make sure you warm the engine thoroughly before giving it the boot!


Edd
 
Ok cheers Edd. I was swithering between 10w-50 and 10w-60 and noticed that Mobil Extended Life is 10w-60 and this is what JMG uses currently I think for turbo's. I was also curious as to whether my noisy lifter would go away with thicker oil and it mostly has.

Stuart
 
I think that 2.5 - 3.0 bar at hot idle is spec for engine so I would have stayed with 10w 40 oil, 10w 60 seems viscous for this time of year.

Nick [:D]
 

ORIGINAL: scam75
Mobil Extended Life is 10w-60 and this is what JMG uses currently I think for turbo's.
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Although most of these turbo's will have 150,000 miles + and therefore consume a fair amount of oil, compared to your recently rebuilt one. High oil consumption was also the reason why BMW specified 10W60 grade oil in their M series cars.


Edd




 
Im presuming that Stuarts increase in pressure comes as a result of using a reasonable quality synthetic -60. It isnt 'too viscous' because its a 10W which is relatively runny. The benefit its greatly improved resistance to getting ever so runny at higher temperatures, which the 951 is renowned for.

I think that the ideal 944 oil is as 'thin' as possible when cold (different cars will take different oils. My 2.7 which is a later design engine needs 15W and my series one car has good pressure and no use on Pro-S 5W) and as resistant to thinning when hot as possible, so ideally a -60, or maybe a -50.

10W-60 is probably ideal.
 
Just changed mine, in the dark. Been using 10w/ 60 Mobil. 2nd change, car had 05/30 or something low when I got it, would see 3 bar when hot, after change no less then 4 bar. Been some long trips. 100 miles+
 

ORIGINAL: 944 man

Im presuming that Stuarts increase in pressure comes as a result of using a reasonable quality synthetic -60. It isnt 'too viscous' because its a 10W which is relatively runny. The benefit its greatly improved resistance to getting ever so runny at higher temperatures, which the 951 is renowned for.

I think that the ideal 944 oil is as 'thin' as possible when cold (different cars will take different oils. My 2.7 which is a later design engine needs 15W and my series one car has good pressure and no use on Pro-S 5W) and as resistant to thinning when hot as possible, so ideally a -60, or maybe a -50.

10W-60 is probably ideal.
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My thoughts exactly Simon. In response to Edd I have new piston rings and new big end bearings in my bottom end, the rest was left alone so will benefit from the oil I put in and I'm fairly comfortable with 4 bar hot idle and my newly quietened noisy tappet!

Stuart
 
Simon you are right. But I would add that if you are going to judge an oil by its ability to stay thicker at higher temps then a more accurate means of doing that would be to look at its HTHS numbers. A High Temperature High Shear test measures the oils thickness at a temperature above what would normally be found in an engine, 150Ëšc iirc (some engines may go above that). It is given in centistokes or cSt. This is where I see the benefit of ester synthetics over mineral oils and even some PAO's, they (esters) have a better ability to stay thicker at high temperatures.

So, for example a ester synthetic like Redline's 5W40 has a HTHS of 4.6cSt, whilst a mineral oil like Castrol GTX 20W50 has a HTHS of 4.1cSt, whilst its 10W40 is 3.1cSt (Redlines 20W50 is 6.1cSt). These are the manufactures figures.

Therefore whilst the Castrol GTX is a 'thick' 20W50 oil, when it gets to 150Ëšc its actually less viscous than the 'thinner' 5W40 from Redline, so not only is the Redline oil providing better protection from cold starts, quicker warm up times, better oil flow and less friction (=more BHP and better MPG). Its also providing better protection at high temps during sessions on track or during hard driving.

Of course there is a major difference in price on the two oils and I'm sure the 10W60 that Stuart has put in his turbo has a very decent HTHS, the only issue is that this is at the detriment of cold weather starts when apparently most of an engines wear occurs.


Edd
 
A bit confused there Edd, thanks for the reply btw, would a 10/40, 10/50 and a 10/60 not all be the same on a cold morning with the "10" being the cold start figure?

Stuart
 
You would think so wouldn't you, but they are not. A 10W40 is usually thinner than a say a 10W60 at cold temps, 10W oils have to fit within a industry standard range of acceptable viscosity's for that grade. As a rule most 10W40 oils are about 90cSt at 40Ëšc and most 10W60 oils are about 125cst at 40Ëšc, at 0Ëšc both oils will be significantly thicker and the 10W60 thicker again than the 10W40.


Edd
 

ORIGINAL: TTM

ORIGINAL: Copperman05
Here we go again...
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Ok, since you insist... 10W60 is better than 10W40 for a 944 turbo engine, full stop [;)]
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But its not as easy at that![:)]Better at what? Which 10W40? Mineral, Ester Synthetic? They are not all the same, as my post above tries to explain.


Edd
 
Ive found Edd, that the more interested and the more enlightened you become, the more frustrated you are too, because its difficult to get all of the information that you want about likely oil candidates.
 
ORIGINAL: Copperman05
But its not as easy at that![:)]Better at what? Which 10W40? Mineral, Ester Synthetic? They are not all the same, as my post above tries to explain.
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Sorry, I meant fully synthetic, I though it was taken for granted already that anything but fully synthetic was not advisable in those engines.
 

ORIGINAL: 944 man

Ive found Edd, that the more interested and the more enlightened you become, the more frustrated you are too, because its difficult to get all of the information that you want about likely oil candidates.
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Indeed, thats why most go with what their indy uses or recommends, which isn't exactly wrong, just not always optimum.[:)]


Edd
 
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