Engine oil choice, CST at 100°c, trying to learn what my engine needs

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G'day. New member, thanks for letting me join up.

I've got a brand new TD42 turbo engine for my Nissan patrol. It'll be running a bit of power so I'm looking for the right heavy duty oil.
Here in Australia I like to run Penrite. They recommend a 15w50, semi synthetic. It's a CI-4 rated oil.


My user manual for the engine states I should run a CC or CD class oil (image attached) Obviously they are obsolete.
My climate rarely puts me below 0°c. Though every now and then I'll be traveling to places that do drop below. The 15w50 is fine for that according to my book.

Now finally to my question. When reading penrites website, and I look at different oils, I see the Cst viscosity at 40°c and at 100°c. The 15w50 is at 19 CST. And another oil I'm looking at is at 14.8 Cst at 100°c. How important is that 5 Cst? To gain a bit better cold start performance when the engine needs the lubrication the most?
 

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Do you have any idea how hot your oil runs now? Even a 10C increase to 110C can make the 15w50 cSt drop to 15. Likewise, run at 90C and the 15w50 could be 25cSt. 15 cst at operating temp is a good aim point. The oil will be hotter and thinner where it needs to work (piston skirt and rings, main and big end bearings) but stiil have adequate viscosity.
 
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I'm sure any HDEO would be fine, I'm guessing CI-4 was specified before ULSD was available, CJ-4 or CK-4 or equivalent ACEA oils should be fine when used with ULSD.
Also, I'd probably stick with 15W40, unless there's some reason to run thicker oil like slowing a leak or you've tuned the thing where the sump is going to run hotter than normar or something, I don't see any reason to go thicker than 15w40.
 

Dogsbody12

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Do you have any idea how hot your oil runs now? Even a 10C increase to 110C can make the 15w50 cSt drop to 15. Likewise, run at 90C and the 15w50 could be 25cSt. 15 cst at operating temp is a good aim point. The oil will be hotter and thinner where it needs to work (piston skirt and rings, main and big end bearings) but stiil have adequate viscosity.
I don't unfortunately. But I plan on running an oil temperature gauge and a cooler if I need too. I'm assuming it's running about 90°c
 
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This is CI-4+, CI-4+ was an extension to CI-4 when they added EGRs to diesel engines running LSD around the 2004 model year in the US and the EGR introduces a lot of nasty soot and other acidic contaminates to the oil, so CI4+ oils should be pretty robust they were the last iteration of HDEO before the introduction of DPFs and ULSD around 2007 in the US. So CI-4+ is high SAPS oil with a nice high TBN, should hold up very well in your old vehicle using modern ULSD and without an EGR, I'm assuming this is old enough it doesn't have an EGR.
 

Dogsbody12

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This is CI-4+, CI-4+ was an extension to CI-4 when they added EGRs to diesel engines running LSD around the 2004 model year in the US and the EGR introduces a lot of nasty soot and other acidic contaminates to the oil, so CI4+ oils should be pretty robust they were the last iteration of HDEO before the introduction of DPFs and ULSD around 2007 in the US. So CI-4+ is high SAPS oil with a nice high TBN, should hold up very well in your old vehicle using modern ULSD and without an EGR, I'm assuming this is old enough it doesn't have an EGR.
That's good to know,
Yes your right I don't have an EGR, so that should work out great.

Though can you please explain how a higher total base number is more efficient? Thankyou!
 
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A higher TBN doesn't make the oil more efficient, but it does generally mean the oil has a greater capacity to buffer acidic combustion contaminants before the oil starts turning acidic, when oil turns acidic it can cause greater wear and the oil more rapidly oxidizes and turns to sludge and varnish.
 
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