Edgy01

Change the oil, and have a good warranty.

Lubrecon

Changing the oil, no matter how frequently, would not have any impact on the overheating condition that Hartech documents.

Quadcammer

Care to explain why you think a 15w-50, which has the same viscosity as a 5w-50 at operating temperature, would be better for track work?

Fahrer

At operating temperatre, the two lubess should have the same/similar viscosities. The 15W-, however uses a higher viscosity base stock than the 0W- or 5W- and, therefore, uses less VI Improver ( polymer) to achieve the viscosity rating at the higher temperature. These polymers are more shear stable than in the past but the viscosity is likely to be a bit less stable than one that uses a higher vis. base stock. The superior lubrication at lower temps (20-40F) are a good reason the use the 0W- or 5W lubes.

Quadcammer

going from a 5 or 15 to a 50 is quite the difference regardless. I haven't seen much evidence of increased shear in a 5w vs a 15.

Lubrecon

Any discussion of cross graded, or so called mulit-viscosity oils, needs to be defined by either mineral oils or "synthetic" oils. Mineral oils that achieve a cross graded status do so by the addition of VI improvers as mentioned by Fahrer in the above post. Even though the VI(viscosity index) of the base stock may be high, as with some Group II or Group III oils, to achieve the wide range, 5W-40 or 50, a VI improver must be used. Today, again as previously mentioned, these VI improvers are very shear stable, meaning they will not lose viscosity to the oil shear that happens in various parts of the engine. That is, they will stay in grade, in most cases until the next drain interval. Of course high speed operation or high load conditions could cause an out of grade condition prematurely.

In the case of "synthetic" oils, which are really not synthetic, such as Mobil 1, the base oil has a naturally high VI, and as such, a wide range product such as a 0W-40, or 5W-50, and be achieved with little or no VI improver as compared to a mineral oil based product. This is because you can start with a higher viscosity base oil, a polyalphaolefin (PAO), with a high VI, and still have the low temp performance in addition to the high end protection. You cannot do this with straight mineral oils, although the Group III oils do approximate a PAO with respect to VI and saturates content. However, not much Group III base oil is used to manufacture a wide range cross graded motor oil because of the expense.

With respect to Quadcammer's comment, you should not notice, or see, oil shear affect any quality product on the market today. either mineral or "synthetic".

I don't want to bore those here with long winded discussion oil engine oils, but most here would be surprised to learn what is and what is not actually a "synthetic" when it comes to oils, either engine or otherwise.

cello

^ No, please do. Its nice to have an expert chime in..

I have used the 15/50 on high temp track days, out of necessity - needed to change it out and could not score the 0/40 locally.

So, any harm in so doing?

stevepow

+1, bore us to tears or until we say uncle. Anyone can choose to stop reading if they get full.

Sean in Texas

Excellent link. Thank you.

pissedpuppy

no way

pabafree95

I agree that a PPI wouldnt pick up a scored cylinder (unless you get comp&leak down) however listen to this clip of the actual sound. I think a PPI would at least identify this as being abnormal.

http://www.youtube.com/watch?v=i9EF96fnujM

Lubrecon

Most here probably use Mobil 1 or Castrol Syntec engine oils I would guess, but there are others "synthetics" available as well. Neither Mobil 1 or Syntec, or any other readily available "synthetic" engine oils are actually synthetic. A true synthetic is a product that does not derive from a hydrocarbon. They are esters, diester, polyol, or other esters, even some vegetable oils . There are other synthetics also, but none widely commercially available in the market place. The "synthetics" on the market today are either a polyalphaolefin(PAO) or a Group III basestock. Mobil 1, and all PAOs, are derived from ethylene, a gas, and a hydrocarbon. The building block for a PAO is decene, a 10 carbon molecule, there is also 12 carbon molecule, dodecene, but enough of the chemistry. The correct terminology, instead of "synthetic" is synthesized hydrocarbon(SHC) and Mobil tried to use that moniker early in the commercialization of the initial engine oil, Delvac SHC. The commercial need for that product came from the Alaskan pipeline, and the desire to not to have to run the engines in the equipment 24 hours a day. It was aimed at the diesels in heavy equipment, thus the name Delvac SHC. Because of the low temperature fluidity of a PAO, very high VI, it was a market home run. The high temp benefits were a second thought because of the climate. However, as it turned out the product was head and shoulders above any mineral oil ever formulated and was easier and cheaper to produce than any true synthetic. That all happened in the early to mid '70s.

Someone, don't remember who, had the great idea to make an automotive product for the public, and Mobil 1 SHC, was introduced in the northern states at first, and then nation wide as the high temp benefit of the oil became better understood and appreciated. The public tended to call the product a synthetic and the SHC was finally dropped from the product name. What the heck, it just added to mystic of such a product that could do so much, so Mobil rename Delvac SHC, Delvac 1, and of course Mobil 1 became the paradigm of engine oils and the premier "synthetic" in the market place....still is BTW. You will still find the SHC label on some of Mobil's commercial and industrial products, they did not stick a 1 on everything.

Now Castrol Syntec. It is neither a synthetic or a PAO. Far from it, it is a Group III basestock, that won the right to be called "synthetic", because of a refining process, hydrotreating, that produced a product with similar specs as a PAO with respect to VI(viscosity index), saturate levels and sulful levels. This happened when Mobil disputed Castrol's calling a refined product "synthetic" and went before the NAD of the BBB with a protest. Well, as they say, the rest is history. Castrol won the dispute because of the similarities of a PAO and a hydro finished Group III oil, and the right to call their product Syntec a "synthetic", just like Mobil 1. I won't argue that the two base oils are close in specs, but Mobil 1 always beats Syntec in all side by side evaluations. Worse, the general public is none the wiser. But the big rub, IMO, is the fact that a Group III basestock is cheaper to manufacture than a PAO, but Castrol does not reflect that in the cost to the consumer. In fact, I have seen Syntec higher priced than Mobil 1. Which of course means that the public is getting ripped off and Castrol makes more money of their product than does Mobil(sorry, ExxonMobil), all because some dorks on some division of the BBB decided it was ok to allow Castrol to use the term "synthetic" on a refined hydrocarbon!!!

As Paul Harvey would say, "And now you know the rest of the story". Or maybe in this case, just the story!!

vexed

Thanks for the info

cbzzoom

I am by no means an oil expert. I've gathered my information from reading at "bob is the oil guy" and other sources. I'm happy to see lubrecon giving us more info.

The short answer is because not all 50 weights are the same, there's a lot more to an oil than its high temp viscosity rating. In general a smaller viscosity range is a stronger oil. This is not true if comparing dino to synthetic, but dino vs dino or synth vs synth seems to be true. My superstition is that you get the best oil performance by using an oil with the narrowest viscosity range that works for your climate and usage.

Also note that "synthetic" has about as much meaning as "organic" - it's a watered down label that doesn't really tell you much; for example it may be hydrocracked dino oil.

Basically under heavy track use, oils do shear, which lowers their effective viscosity, so eg. a 50w becomes a 40w. Under road use this might take 10-20k miles, but on track it can happen in 1k miles. Certainly old wide-range dino oils were very prone to losing viscosity under heavy use, because the viscosity-modifier package would break down.

Of particular note, the Bobit guys really don't think much of Mobil 1 0w-40 , they say it's very shear unstable and rapidly turns into a 30 weight. Apparently our large sump helps with this somewhat - the worst problems are in small oil capacity engines. There is some controversy on whether this actually matters or not. Some think that M1 0w40 is intentionally designed to shear, so that over its very long lifetime it is compensated by oxidative thickening.

You should be able to see oil breakdown yourself if you pay close attention to your oil pressure gauge. As the oil shears, the pressure will drop, so if you take readings right after an oil change, and then readings again after a few track sessions, you have a rough idea of whether the oil is maintaining its viscosity or not.

Really this is only something that people who do hard tracking need to worry about, and they should really be using UOA and oil pressures to make their decisions, not hearsay.

I do believe that the early Porsche recommended OCI of 20k miles was a mistake (which they seem to have realized as they revised it downward over the years).

edit : BTW I don't mean to imply anywhere that oil type is significantly related to Paba's problem at all, just an amusing sidebar.

stevepow

OK, so with the choice of 0w-40 or 5w-50 for most of us living above -13F, which would do better and why?