Lower oil pressure with SAE 30?

[jdkline]

Yeah....I wonder if this would be expected. With the 15-40, it was 15-20 at hot idle, with the straight 30 it is 11-15 at a hot idle. In both cases, the oil pressure is well over 40 on a cold startup or moving down the road at 2000+ rpm, within specs.... what are you guys with real oil pressure gauges seeing and would anyone figure this for a problem?
J.D.

 

[The Warden]

I would have assumed that the idle oil pressure would have been slightly higher, while the operating speed oil pressure would have been slightly lower. Are you getting the oil pressure readings from the stock location, or from where?

Have you tried SAE 40? When it gets warm enough out there, it might be worth a shot...

Just some thoughts...good luck!

 

[jdkline]

Tim, SAE40 is off spec for the IDIs by the book, but that doesn't mean it can't be run obviously..... the reading is coming from where the factory idiot gauge is plugged in, mechanioal gauge along with the same old factory idiot light on a tee

 

[The Warden]

Ah, okay

I checked my manual and you're right...but I don't see why SAE 40 couldn't be run in warm temperatures. Looking at my chart, it says that 15W-40 can be run above 0°F, 20W-40 can be run above 10°, and SAE 30 can be run above 30°F. To me, that implies that SAE 40 could be run above 50°. I imagine it doesn't cool down that much at night in Florida during the summer, although I would be apprehensive about running it in the spring and fall...

Hopefully someone with more experience will chime in, but I think it's safe during summer...

 

[yogi_160]

wow a literacy test who said sae 40 i believe the question was sae 30

 

[The Warden]

wow a literacy test who said sae 40 i believe the question was sae 30

Uhh...did you miss parts of the thread? Here, I'll recap:

Have you tried SAE 40? When it gets warm enough out there, it might be worth a shot...

SAE40 is off spec for the IDIs by the book, but that doesn't mean it can't be run obviously.....

but I don't see why SAE 40 couldn't be run in warm temperatures. <snip> To me, that implies that SAE 40 could be run above 50°.

I was offering a suggestion on a possible alternate, and we were discussing the merits of it.

 

[Agnem]

I don't know why you'd get a lower reading with the 30Wt. You could always try the 40wt for a brief time. I would think the concern with 40wt, is that any oil tends to thicken as it ages in these motors, and there may be a cold start concern. Just about any oil when hot, seems the same viscosity if you ask me, but then what do I know about oil?

 

[NJKen]

you got a lower pressure with the 30wt because hot 30wt is thinner than hot 15w40. The 15 in 15w40 is the oils cold viscosity. The 40 is what the oils viscosity would be equivilant to of hot 40wt oil. By using the 30wt you are only getting the viscosity of hot 30wt oil thus lower pressure. Usung 40wt is probably a bad idea. That oil will not want to get out of that pan and into the engine beraings where it belongs because it is just too thick. The 15w40 has a viscosity similar to cold 15wt oil. that is a big jump.
The oil industry uses a lot of viscosity improvers to get the multi wieght oil and the further the swing (10w30 vs 10w40 for example) the more viscosity improvers and less oil. By going synthetic the eliminate some of the viscosity improvers. Have you tries a 15w50 synthetic yet?
Ken

 

[timntools]

you got a lower pressure with the 30wt because hot 30wt is thinner than hot 15w40. The 15 in 15w40 is the oils cold viscosity. The 40 is what the oils viscosity would be equivilant to of hot 40wt oil. By using the 30wt you are only getting the viscosity of hot 30wt oil thus lower pressure. Usung 40wt is probably a bad idea. That oil will not want to get out of that pan and into the engine beraings where it belongs because it is just too thick. The 15w40 has a viscosity similar to cold 15wt oil. that is a big jump.
The oil industry uses a lot of viscosity improvers to get the multi wieght oil and the further the swing (10w30 vs 10w40 for example) the more viscosity improvers and less oil. By going synthetic the eliminate some of the viscosity improvers. Have you tries a 15w50 synthetic yet?
Ken

ok, I get all this, then what should we go with? the str8 30? or something like 15w-30...

or syn 15-30.

 

[jdkline]

WellI posted a few days back about trying SAE30 to improve my wear numbers. I was just going to run it 2K or maybe 2500 miles adn send a sample to Blackstoine and see what they say ro me. I don't know waht's better, I'm trying to figure it out,
J.D.

 

[NJKen]

ok, I get all this, then what should we go with? the str8 30? or something like 15w-30...

or syn 15-30.

15w30 would flow better cold that sae30 but have the same properties hot. 15w40 seems to be about the best combo for general diesel. Once ina while you will see a spec for 20w40 or something odd like that but the general requirement is 15w40.
Ken