Oil weight

[rawavr4]

Stealthee, where did you get 20w-50? I cant find i anywhere.

[GordonRamsey]

The walmart I go to doesnt have it.

[stealthee]

Stealthee, where did you get 20w-50? I cant find i anywhere.

I dont use Rotella 20w50 if thats what you are asking. I just run cheap ass oil as I have 190k miles on my car. Well theres about 120k+ on the engine, but between what it leaks and the little it burns it would be wasteful for me to use anything else.

[rawavr4]

No, i was just wondering where in to get it in general. No places around Easton sell it that I know of.

[stealthee]

Every place I've ever bought oil from has 20W50.

[blindmist]

I know Aimsoil is real good. But I cant find much of anything anywhere. Pep boys was where I was at today, and even they had a small section.

You have to find an Amsoil dealer. There is really no store that sells it. Not like Autozone.

Also, I just went to my Walmart in Lubbock, Texas, I could not find and 20w, highest I could find was 15w.

[Mean Green]

Rotella at walmart is only about 11$ for the big jug. No sense in running Amsoil unless your car is boosted and you beat the shit out of it. Royal Purple is really good as well but I have always run Rotella in every car I've ever owned.

Rotella 15-40 w/ Purolator Pure One oil filter FTW.

[GordonRamsey]

^ thats exactly what I got.

[bluemax_1]

Wow... talk about some ridiculous and terrible so-called 'information' in this thread. Any tribologist would cringe.

OK, the topic is oil weight so listen up (read up?)

Oil weight is a measure of its viscosity or flow rate at a given temperature. Multi grade/viscosity oils like 5w30 or 20w50 are labeled as such from flow rates measured at 2 different temperatures, a cold flow rate and a hot flow rate.

These measurements are referred to in 2 commonly used units of measurement:
- centipoise (cP or mathematically, mPa.s) called the dynamic viscosity or simple viscosity

and the other unit of measurement (which is more commonly referred to in the US)

- centistokes (cSt or mathematically, mm squared/s)

- There is a 3rd unit of measurement, which is SUS (Saybolt Universal Seconds) where they measure how long it takes for 60 milliliters of a fluid to flow through a calibrated orifice in a Saybolt viscometer.


These measurements are made using a viscometer. The hot flow rates were initially measured at 210f in the original SAE J300 rating system in 1911, and later revised to 100c/212f in 1926. In 1952, they added the Winter (cold flow) rating, to address the difference in protection/properties between oils refined from black Gulf Crude vs. amber Pennsylvania crude. The amber Pennsylvania crude gave better cold protection (had better/lower cold viscosity) than oils refined from the black Gulf crude and the SAE began measuring cold flow viscosities at 0f to label the cold/Winter flow properties. The measured flow rates of a specific oil formulation are then labeled according to the viscosity range the SAE has spec'ed for a certain oil weight (i.e. a cold viscosity of 0, 5, 10 or 20, and a hot viscosity of 20, 30, 40, 50 or 60).

There are 2 other measurements that most folks aren't aware of or concerned with. These are the HTHS (High Temperature, High Shear) measurement, taken at 150c, and the cold cranking and pumping dynamic viscosities. The HTHS indicates the oil's performance under harsh conditions and its hydrodynamic fluid film strength (very important for highly loaded engines). The cold cranking and pumping measurements show the oil's viscosity at temps below 0c.

Understand that because the 2 numbers in a multigrade oil are taken at different temperatures, they CANNOT be compared to each other. What a 10w30 rating means is simply, "This oil flows like a 10 weight mineral oil at 0f, and flows like a 30 weight mineral oil at 212f".

These are the SAE determined hot viscosity ranges (at 100c):
SAE 20 = 5.6 - <9.3 cSt
SAE 30 = 9.3 - <12.5 cSt
SAE 40 = 12.5 - <16.3 cSt
SAE 50 = 16.3 - <21.9 cSt
SAE 60 = 21.9 - <26.1 cSt

A 10w30 oil has a viscosity of about 90 - 110 cSt at 40c(104f), and at operating temperature of about 212f, it should have a viscosity between 9.3 - 12.4 cSt. BUT at 0f, a 10w30 can have a viscosity of over 500cSt!!!

Just for reference here are some common kinematic viscosities:
Water at 20c = 1 cSt
Milk = ~4.3 cSt
Tomato juice = ~220 cSt
Honey = ~2200 cSt (about the flow rate of Lucas oil additive near 32f ).

So now you know what the oil weights are and what the viscosities are like at different temperatures. But what does it all mean?

Well, an engine (when new) is designed to be lubricated by oil of a certain viscosity range within a specific flow rate (vs rpms) at optimal temperatures. At higher temperatures, the oil thins out more, so at higher temperatures, you need a thicker oil to maintain the appropriate viscosity range to adequately protect the engine. There are also limits to the maximum viscosity the engine can pump and lubricate properly at (especially when cold) so you can't go too thick either (especially the colder it gets). This is why Mitsu specified 10w30 for most use and 20w50 in very hot temps. These recommendations are based on dino oils though (because they're aware that some folks prefer putting the cheapest thing they can find in the car).

Some newer cars, (as others have mentioned) spec thinner oils because they're designed with tighter tolerances (and potentially lower loads). Many of these new vehicles spec 0w20 oil because the thinner oil increases fuel economy (thinner viscosity = less fluid drag = better efficiency). If the engines are properly designed for it, there's no problem. Granted, there have been some folks who've had problems with using 0w20 in vehicles spec'ed for it, because the manufacturer spec'ed the oil mostly for fuel economy to allow higher mpg ratings, but the oil doesn't provide enough protection under more severe use, so folks driving harder blew their engines.

Anyway, to get back on track, the appropriate viscosity range oil for a particular car is dependent on the engine's tolerances (bearing clearances, power output, redline, oil pump flow etc.), operating conditions and temperature range. You need thinner oil for lower temps and tighter bearing clearances. Thicker oil for higher temps and greater bearing clearances. A high HTHS is important for highly loaded engines (turbo and especially modded turbo folks). Contrary to what folks might think, higher power does not necessarily automatically dictate a super thick oil. Generally, if you can run a thinner oil at higher flow rates, you're better off than a thicker oil at lower flow rates, however, the hydrodynamic fluid film strength is critical and the HTHS is an indicator of that. Why do I like Red Line so much? It has one of the highest HTHS ratings available for a given weight oil.

The 6G72 engine is designed for an optimal viscosity of about 10cSt at proper operating engine temperature (as are many other vehicles) at normal loads and ambient temperatures.

In practice, the theory is simply. You want the oil viscosity to be as close to 10 cSt as possible at ALL times, regardless of whether it's 40 below in Canada or 130f in Death Valley. If there was an oil with good lubrication properties that stayed at 10 cSt no matter the temperature, there would be no reason to ever buy anything else. Unfortunately such a fluid doesn't exist, which is why there are multigrade oils. The idea is to have an oil that is thinner at low temperatures so you don't see the insanely high viscosities (and therefore reduced flow) on cold startup, but one that doesn't thin out too much when the engine gets up to its normal operating temps.

With dino oils, they start with a lower viscosity base oil and use a combination of VII's (Viscosity Index Improvers) and PPD's (Pour Point Depressants) to achieve a decent multigrade. For example, a 10w30 dino may be made from 20 weight base stock with VII's added to stop it thinning out more than an SAE 30 weight at 100c, and PPD's to produce decent flow rates like a 10 weight at lower temps. VII's are long chain polymers. At lower temperatures, they remain coiled, at higher temperatures, they uncoil but to a limited amount, thereby limiting how much the viscosity thins out. The problem is, these polymer chains can be sheared, mechanically or chemically. When these VII's permanently shear, they can no longer inhibit the oil thinning out at higher temperatures and you now have the protection of a 20 weight oil at operating temps (or less at higher temps). I can tell you that this sure as hell isn't enough for a 6G72TT. Could you get away with it on an NA? I don't know. If driven very lightly and carefully (like the nutters putting Regular gas in these cars), you might be able to save some pennies (cheaper gas + better fuel economy from thinner oil). My advise though, would be to get a Kia.


Max

*** post too long, continued below

P.S. This post wa originally posted at about 10p.m. EST 10/18/10, don't know why it appears in the middle of the thread as posted at 2:55P.M.

[bluemax_1]

continued...

The reason I dropped Mobil 1 0w40 like a hot rock is because this damn oil sheared to about a 20 weight in a very short time in my VR4, and this was with normal street driving. I hadn't even tracked the car yet when I did the UOA out of curiosity, which I'm glad of, because I discovered that there are a couple of people who've spun a bearing roadracing a 3/s with Mobil 1 0w40. Based on how fast the oil sheared in my engine, I think that a BPU (or higher) car could shear this particular oil within 3-4 flat out laps on a roadcourse. After that, a spun bearing is just a matter of time.

The thing is, even a 0w oil is too thick at 70f, much less 0f, so optimally if we could find a 0w30 oil (0 weight is the lowest cold viscosity oil available) that didn't shear/thin out, this would be absolutely ideal for a like new 6G72 engine with factory power output, driven in ambient temperatures around 65f - 80f that isn't run too hard. Problem is, not all oils are created equal (and some engines are harder on oils than others). Just about ANY 0wXX oil uses some VII's and PPD's. And the problem with VII's as I've mentioned, is that if/when they shear, you're left with the viscosity of whatever base oil it is they were using in the formulation.

Synthetics on the other hand have inherent multigrade properties. True synthetics can be formulated to a 10w30 with zero VII content. They also inherently flow better at lower temperatures. Red Line and Motul 300V can both formulate 10w40 oils with little to no VII's, meaning these oils won't shear down even under hard use. Under extreme temperatures, they will thin down to a lower cSt (as all oils/fluids do at higher temps), but synthetics tend to thin out less at higher temps than dino oils do (even Grp III hydrocracked oils) which is why a synthetic 10w40 can have a higher cSt at 230f than a 20w50 dino. And without VII's to shear, at a given temp, you will have the same viscosity as when you poured the stuff in the engine (barring outside contamination like dilution from fuel or coolant).

With my VR4 specifically, after discussing the specifics with one of the chief tribologists responsible for developing Motul's current 300V formulations, the recommendation was for the 10w40. He recommended their 5w40/5w30 for daily driving and their 10w40 for track use. This is for a 6G72 that is spec'ed for:
- Rod and main bearing clearances of about .00018"
- 8000rpm redline
- ~550awhp
- oil temps of ~230f

For anyone to say that a 0 weight or 5 weight oil is too light is to demonstrate their ignorance of tribology. While it's true that I personally would never use a 0wXX in the VR4 for roadcourses, for normal driving without track use (especially if I drove it in the winter), I would consider trying a decent 0w30 or 0w40 (Red Line now has 0wXX formulations) contingent on UOA's to see how the oil holds up. I HAVE used 5w30 and 5w40 oils in the VR4 in the winter and it's been great, even with my Tommi Makinen impressions whenever there was more than 4" of snow on the roads (what can I say, I miss my amateur rallying days). The oil held up just fine in UOA's. Then again, I don't use cheap stuff either. After trying Mobil 1 0w40 years ago (will NEVER use that stuff in a VR4 again) and Royal Purple 10w40 (sheared to a low 30 weight almost a high 20 weight within ONE track visit), it's been Red Line or Motul 300V for the VR4.

Saying that so and so's car blew something BECAUSE they ran the recommended 5w30 with NO reference to what oil it was, what the OCI was, how the car was run, little to no background on the car's condition etc. is akin to saying that carrying Wrigley's chewing gum in your pocket while walking around will result in a twisted ankle because someone you knew twisted their ankle while carrying a pack of Wrigley's gum in their pocket while walking around.


Of course, oil weight is just part of the equation, the actual formulation of the oil is important because there are also boundary lubricants, EP, AW additives, ester vs. PAO vs dino vs. Grp III hydrocracked stock etc.

As far as extended OCI's (Oil Change Intervals), that greatly depends on the car, the oil and how the car is driven. All street oils contain detergents to clean the engine, and they also contain acid inhibitors. The byproducts of the combustion engine, unfortunately can eventually turn the oil acidic. Street oils are formulated to a TBN (Total Base Number) which some UOAs (Used Oil Analyses) will display. If the oil is fairly common, or something the specific company has done a VOA (Virgin Oil Analysis) of, then you will have VOA vs UOA numbers to compare. The ONLY way I would advocate anyone trying extended OCI's is WITH a UOA (otherwise, you could potentially be asking for trouble). The UOA will show if your wear metals are within decent parameters, if there is any contamination from dirt (which would increase wear), if there is fuel contamination, if the TBN is too low (for some reason, your car is using up the acid inhibitors more quickly), if the particular oil you're using has sheared to a lower viscosity etc. If all, these parameters are fine, you can certainly extend your OCI's.

That said, WITH UOA's, I've discovered that with MY VR4, I can run 7,000+ miles on a single fill of Red Line 10w40. Potentially 10,000 miles or more (WITHOUT track use). 7,500 miles is the longest OCI I've ever gone though (with 1 track day). The wear metals were a little higher than I would like, but only to be expected (and still acceptable) given the track day. TBN was still good enough and wear metals were low enough to continue using the oil though. So yes, with a good oil, you CAN potentially run long OCI's. As mentioned though, I wouldn't recommend it without performing UOA's. Any significant fuel dilution, coolant leakage/mixing with the oil, dirt contamination from inadequate air filtration or any myriad of seemingly small issues can greatly reduce the oil's usable life though, and of course, as I keep saying time and again, not all oils are created equal.

But I'll leave that for another time, since I've come to realize that there are folks who like reading my posts, but there are also some who like to take some of the information from my posts and regurgitate it to sound knowledgeable without fully understanding what it means. Makes it more fun to correct them later.


Max