Trying To Make Sure I Understood Oil 101 Correctly

Joined
Sep 21, 2014
Messages
1
Location
STL, MO
I am trying to make sure the information was interpreted correctly. So it seems no matter what, you would want a 0w-xx oil. You should also run as low of a grade as you can with still maintaining 75psi @ 6000pm. Higher grade increases oil pressure, while lower grade lowers psi. Are the above 3 statements true?
 
Joined
Dec 11, 2013
Messages
4,597
Location
Manchester, England
On most modern stuff, yes twang a 0wxx (bearing clearance dependant - there are still cars on the road that spec a SAE50 mono) Maintaining 75psi is engine based, some like more and some like less It would appear that way based on the location of your pressure sensor, but it's more likely you're just increasing the psid across the filter. As I understand it, pressure is dictated by the volume of flow and the bearing clearance.
 
Joined
Nov 18, 2005
Messages
10,146
Location
Burlington, Ontario, Canada
Generally speaking 0W-XX oils are lighter on start-up at all temp's because they tend to have a higher viscosity index than 5W oils and of course 10W oils. But there exceptions so it's always best to check the actual viscosity spec's from the companies Product Data Sheets. Yes oil pressure correlates to operational viscosity in an engine but for the actual OP spec' for a given engine you should go by what the manufacturer recommends. 75 psi @ 6,000 rpm would be fine for my Porsche, BMW (a bit high) and Caterham too high for some engines as the oil pump will be in by-pass mode.
 
Joined
Jun 24, 2004
Messages
14,505
Location
Top of Virginia
I wouldn't take away any "absolutes" from that article, but I do think that it's mostly on target.
Originally Posted By: Dlauth
So it seems no matter what, you would want a 0w-xx oil.
In general, a 0W-xx would be preferred to a 5W-xx or a 10W-xx, especially if you're paying the same price for it. For example, if you're buying a synthetic oil anyway, you might as well get the benefit of lower startup viscosity while maintaining the same viscosity at whatever xx grade you pick. But there are, of course, a variety of other factors. Is your engine under warranty, and is a 0W-xx allowed? If you're cross-shopping conventional 5W-xx or 10W-xx oils, are you willing to pay more for the synthetic product to get the better startup flow? Different people will answer those questions differently.
Originally Posted By: Dlauth
You should also run as low of a grade as you can with still maintaining 75psi @ 6000pm.
There is probably a point for every engine beyond which you get significantly diminishing returns for going "up" a grade (and vice-versa). Some have the saying, "as thin as possible and as thick as necessary". Similar to what is posted above. The concept is to not run an oil thicker than necessary to achieve the correct oil pressure for your engine. I wouldn't assign an absolute value to it (like 75 psi @ 6,000 rpm), but I would check your engine's service manual.
Originally Posted By: Dlauth
Higher grade increases oil pressure, while lower grade lowers psi.
I think that statement is generally true.
 
Joined
May 8, 2011
Messages
820
Location
Sacramento CA
Originally Posted By: Concours14
shrug What's your owner's manual say? That's the bible, the gospel, the ultimate Truth and Wisdom. Especially under warranty. horse
Agree. Its just too easy for some to follow. We waste a lot of time splitting hairs.
 
Last edited:
Joined
Oct 16, 2010
Messages
2,093
Location
.
The essence of the article you cite is "as thin as possible, as thick as necessary". And that's where the arguments begin. Saying any oil is fine as long as it provides 75 psi is probably wrong as each engine and generation of engines have different requirements. If you want to follow the thin/thick guidance I'd suggest starting with your owners' manual recommendations. If it specs, for example, a 10w-30, check the 100C cSt and HTHS value of a major maker product (Mobil, Shell,etc.). If you want to find a suitable 0w-30, first make sure its cSt and HTHS values are close to these values. If they are, it should be a good match. This will mean that, if your engine is spec'd for 5w-30, a 5w-20 or 0w-20 won't be appropriate as they will not be as thick as your car's manufacturer thinks is necessary.
 
Top