So... you think you understand motor oil. Think again...

[Boostwerks.com]

Interesting read from a very knowledgeable engineer...

http://ferrarichat.com/forum/faq.php?faq=haas_articles

Enjoi

 

[bcmaxx]

How do you become a doctor of Motor oil? What school would one attend?

 

[scottmcneal]

Lube dot com...

 

[winterbeater]

Yeah, we've covered all this before. And then there is ZDDP. XJ'er don't believe the thin oil stuff anyway. Most like a 15W-50 and think it's what holds their motors together.

Try this: http://www.bobistheoilguy.com/cms/

 

[Boostwerks.com]

To sum up for those lazy enough to not read the entire article...

Pressure isn't everything (like what most motor heads will tell you). A good combination of pressure and flow is what lubes a motor. An oil should be selected for a motor that results in a nearly 1:1 ratio of 10psi per 1000rpm. This will allow the oil to flow at it's highest rate without causing the pumps bypass valve to open (wasted film strength).

For anyone that has taken a college level fluid dynamics course will agree with him 100% (me included).

According to the data i've collected from my turbo charged 4.0l, the 10W40 is way too thick for the motor. At idle I have nearly 30psi, and the pressure maxes out around 65psi past 2500 rpm. By using this data I should be able to use a 0W20 for the maximum amount of film strength in the motor

My testing with road racing cars also confirms his theory. I was using a 10w40 in my race car which see's revs in the 8-9K range for long periods of time. Even with an oil cooler the motor would start to get hot and my oil pressures would stay stagnant. After switching to a 5w30, the oil temps went down and the motor stayed cooler for longer periods of time.

 

[01grn_xj]

Good article! Definitely nice to get some of the myths out of the way.

 

[kastein]

iiiiinteresting.

Honestly, I only run 10w40 or 15w40 because it takes longer to leak out. Normally I'd throw the same 10w30 or 5w30 semi-synthetic into it that I would run in anything else.

 

[Talyn]

When the additives wear out in a synthetic oil it still has the same viscosity. It will not thin as a mineral oil.

That is incorrect. Having done oil analysis using synthetic oil on various engines the oil tends to thicken as it gets used up. I have seen this on synthetic oil, but have not done an analysis on dino oil.

The author then contradicts himself later in reference to synthetics:

It will never thin yet has the same long term problem as the mineral based oil. They both thicken with extended age.

 

[Hellbent]

there's a couple minor points where he either *almost* contradicts himself, or doesn't quite seem exactly certain as to what he's trying to say, but overall that really is an excellent article. the time spent to read it is certainly worthwhile.

 

[Boostwerks.com]

That is incorrect. Having done oil analysis using synthetic oil on various engines the oil tends to thicken as it gets used up. I have seen this on synthetic oil, but have not done an analysis on dino oil.

The author then contradicts himself later in reference to synthetics:

The way he wrote that is confusing, but what he's trying to say is that the thining affect due to the elimination of the additives over time doesn't occur in a synthetic.

BOTH oil's thin over time and eventually thicken, but the relationship of the additives to the oil doesn't have that big of an effect on the oils viscosity as it does a mineral based oil. This explains the reason for the longer change intervals for synthetics.

Synthetic oils are a whole different story. There is no VI improver added so there is nothing to wear out. The actual oil molecules never wear out. You could almost use the same oil forever. The problem is that there are other additives and they do get used up. I suppose if there was a good way to keep oil clean you could just add a can of additives every 6 months and just change the filter, never changing the oil.

 

[winkosmosis]

There's something I want to know about oil viscosity. Isn't there a benefit to an oil that has a thicker cold viscosity, because it will cling to the engine parts better between runs?

 

[Boostwerks.com]

There's something I want to know about oil viscosity. Isn't there a benefit to an oil that has a thicker cold viscosity, because it will cling to the engine parts better between runs?

He addresses that...

Some people have said they use thicker oils because they only use their cars every 2, 3 or 4 weeks. They are afraid that thin oils will fall off the engine parts and result in a lack of lubrication at startup. Think about your lawn mower over the winter. It gets gummed up solid. The oil and fuel thicken over time resulting in engine failure. Anyway, oil on the surface of parts does not lubricate. It is the FLOW of oil between parts that lubricates. Thick, old, waxy oil can only be bad.

 

[ebjones7]

Great article! lengthy but very interesting! a good hour spent reading that. haha