bgiere

Unless you are doing used oil analysis tests all you are doing is speculating...it is that simple...."because my mechanic said so", "because the previous owner...", "because it is hot",etc,etc is all worthless worry and conjecture....I'm not trying to be a smart@$%, but unless you test it you cannot make a statement about oil and its efect on your engine. It's really that simple!!

texas911

I thought my 997 took 10 quarts of oil.

ceboyd

...heck, even my boxster S takes 9.5 quarts of oil IIRC

geolab

Please keep in mind that the wider the viscosity spread, the better the oil is, ALWAYS.
In english, a 5W-50 oil is far more better than a 10W-50 or a 15W-50.
so a 10W-30 is of lesser quality than a 15W-40. the first has a spread of 20 points, the latter 25pts.
if u have the same spread with different grades, that is, 5W-30 and 15W-40, then you should consider the time of the year in which the car will run. The lower W figure for cold.

The largest spread on the market today is 50 points.
We can find competition grade oils with such viscosity as the CASTROL RS 10W-60.
these are good for old engines. the viscosity stays dense at high temperatures, and of course for racing.
If you use it on a good engine, you might see your pressure gauge stay high. Some sellers use the trick, but these oils are the best.
A 5W-50 oil? I think this is excellent two.
As to the brand I don't bother much (knowing this is going to bother some who stuck a lifetime with the same brand). Since these oils with such viscosities are forcefully 100% synthetic, they are all good.
Only difference between brands are the additives, but as Porsche preconize, the less additives the better.
When is the real WEAR your engine takes most? when is the friction the most killing?
the moment you turn it on . . .

the first few seconds of cold run are the most criminal.

this is why we still need less viscous oils in cold start and viscous in warm.
that is, the best scenario would be a 0W-60 but for this we have to wait.

conclusion to me, if you run your car normal, go for the widest spread that you find everywhere in stores.
If you push it, go for higher viscosity spread. Thus 10W-60 where you find this oil at special stores.

0W-40 will be consumed faster than a 15W-50 on a race track? OF COURSE. at constant high engine temperatures, the 0W-40 is thinner and less viscous than 0W-50.
But for everyday use, the 0W-40 will lubticate the engine faster the few seconds of starting the engine, thus less wear.

george


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'97 carrera S 100% original

ceboyd

thanks... so can I safely conclude that I'd be o.k. to mix my 6 quart pack with 4 more quarts of say valvoline synthetic 20w50 ..... or even castrol synthetic 5w50? ....because it seems mixing brands isn't a big issue.


I'd feel better staying away from the 'more additive' gold cap even though many of you are telling me it's superior and just find for my 993. I'd rather go with less additives (more towards race oil) and change the oil more frequently. (I guess that's just me)

Flying Finn

So how did you test your oil and came to a conclusion that 0w-40 is better than 15w-50? And in which way was 0w-40 better, what are the benefits?

Or are you simply saying so because Porsche is saying (main reason being hydraulic lifters) so?

I'm using the thicker 15w50 since I drive at the track often and in general, temperaturs here are prtty much always warm, if not hot.

geolab

First, I would never mix oils, even if they are produced at the same refinery (AT THE END). Different brand oils have different additives compositions and might clog. The reason behind that is for example one oil uses ceramic as additive, and the other metal hybrid. the ceramic will clog with the metal hybrib.
I personnally use mobil1 5W-40, I find it everywhere here in europe and price is reasonable. The engine consumes one quart per 1000kms and its totally normal.
Last year, I travelled from Paris to south of Turkey with the car, so before, I changed the oil and filters, and I used a 10W-60. The car ran for 36 hours with a stop in between for about 4 hours only. Distance crossed was 4000 kms and the car only consumed 1 quart. Did that because I knew the car was going to run at around 5000-6000 rpm constantly whenever possible. (practically no speed limits from germany to turkey)

All this to conclude that the more cold-starts, the less viscous the oil should be or less .W figure. The more track, the more viscous the oil should be and thus the higher the second figure should be.

Imagine the frying oil at home. When the oil is cold, it is thick. When you heat it up, it is very liquid.

The scenario in an engine should be the exact OPPOSITE.
Cold engine oil should be liquid to lubricate the engine fast at cold start, and thick when oil and engine is hot, to still lubricate and stick on metal.

0W-40 better than 15W-50? quality wise (technically speaking) it is. The viscosity spread is larger, 40 points with the first.
If I want to drive my car on a track? I will use 15W-50 because the oil stays viscous at higher temps than the 0w-40, and I will be cold-starting my car less.


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'97 carrera S 100% original

Edward

Exactly.

And on viscosity choices, one should "weigh" one's use, driving habits, and climate; not the dealer's party-line-recommendation ...they have NO options as they recommend only what they sell. Recall that 5 and 10 weight synthetics were widely available back at the inception of the 993 in 1994. So arguing that this "new" grade is beneficial misses the point entirely. Choosing viscosity depends on your needs. Brands and formulas aside, the "better" oil is the one that suits your particular use.

And remember, too, that an air/oil-cooled car has markedly different rates of metal expansion than a water-cooled engine which enjoys a narrower operating temp range.

All just food for thought ...choose as you will.

Edward

Bull

OF COURSE!

bgiere

Flying Finn, i noticed a decrease in Copper and Aluminum after running 0w40 in both my 964 and 944 race cars compared to the 15w50...in the 964 i had lower oil temps in 30 minute sprint races....for the 944 we do not have an oil temp gauge so i do not know if that is the case or not. Both samples were run at Blackstone labs. My last sample was a 5w40 Mobil 1 and the test came back showing fuel dilution (i had a bad injector) so the results were diluted and metals were elevated. That was a case where a higher viscosity may have been helful if i conitnued to run with this bad injector. The oil had sheared to a 30 weight...I don't think i had any long term damage done but i will sample it again after 10 hours of running time. I am not towing the company line at all, it's just that my personal experience and testing backs what Porsche has recommended. I wouldn't see any reason for an engine manufacturer to recommend the wrong lubricants.... Imagine the warranty costs they would incur. Your experience may differ, but you will not know for sure unless you send in a few samples. A test costs $20 with interpretation from the lab.

Flying Finn

Thanks Brant,

This kind of answer I was hoping (and actually expecting) for. I've been thinking of doing a testr and wanted to hear first hand experoience on this, especially when driven at track.

Thanks for the info, very much appreciated.

bgiere

No problem...i went through all kinds of different oil strategies/beliefs and finally found peace after some oil analysis!

ceboyd

o.k. then no mixing brands for me then! thanks much!



...what about mixing viscosity?

can I use my 6 pack of mobil 1 15w50 red cap with 4 quarts of mobil 1 0w40???

anyone?

geolab

I couldn't help but include some interesting literature to the averts:

Porsche reply on the 993 engine:

The viscosity grade is the concern of the original engine manufacturer and designer. Porsche tested the 993 engine on a 40 grade oil and recommend such. A 50 grade doesn't go down well with the hydraulic tappets. Also generally a more viscous grade causes a greater temp increase in the working areas of the bearings which is undesirable.

Bob Cord (development engineer/ Cosworth):

the oil continues to get runnier as it heats up further and further. If you run a max temp in the gallery of 130 you will probably see 150 in the big ends (somewhere in between for the mains). A 0W40 oil thins less with temp than a 15W40. Therefore at 150°C the 0W40 will have a higher viscosity and provide a thicker bearing film event though they have the same visc at 100°C.

The HTHS (high temp high shear) viscosity can vary a lot. This isn't quoted so often. A modern 0W30 such as Castrol SLX(stock Audi fill)will have a HTHS of 2.9 groats but the special oil for the RS4 (which is still classed as 0W30) is 3.5. Mobil 1 0W40 has an HTHS of 3.6 and 15W50 is 5.1. Castrol RS 10W60 is 5.7. The trade off using oils with high viscosity is that even though they protect bearings at high speed they will increase friction and sap power. Looking at the Mobil website it claims they supply Maclaren Mercedes with 0W30 racing formula. Not very thick at all.

I guess it comes down to what the designer has specified during the bearing calculations. Porsche uses 5W40
I think as long as you use a reputable synthetic oil there is no need to go above a 40 weight oil, you'll just lose power and make heat unless you have an RS or similar rated engine when the 50 wts will be over benefit. If Porsche are satisfied with 40 then I'd stick with that.

article written by John Rowland, Silkolene/Fuchs Chief R & D Chemist for 40 years.

Quote:

Costs of synthetics vary considerably. The most expensive are the “Ester” types originally only used in jet engines. These cost 6 to 10 times more than high quality mineral oils.

The cheapest synthetics are not really synthetic at all, from a chemists point of view. These are in fact specially refined light viscosity mineral oils known as “hydrocracked”. These have some advantages over equivalent mineral oils, particularly in lower viscosity motor oils such as 5w-30 or other oils with a low “W” rating such as 5w-50 etc and they cost about 1.5 times more than good quality mineral fractions. We use several different grades of this base oil, where appropriate.

This is the “synthetic” which is always used in cheap oils that are labelled “synthetic”. Yes it’s a cruel world, you get what you pay for!

Now, you may ask, why are these special mineral oils called “synthetic”?

Well, it was all sorted in a legal battle that took place in the USA about ten years ago. Sound reasons (including evidence from a Nobel Prize winning chemist) were disregarded and the final ruling was that certain mineral bases that had undergone extra chemical treatments could be called “synthetic”.

Needless to say, the marketing executives wet their knickers with pure delight! They realised that this meant, and still does, that the critical buzz-word “synthetic” could be printed on a can of cheap oil provided that the contents included a few percent of “hydrocracked” mineral oil, at a cost of quite literally a few pence.

So, the chemistry of “synthetics” is complex and so is the politics!

The economics are very simple. If you like the look of a smart well-marketed can with “synthetic” printed on it, fair enough, it will not cost you a lot; and now you know why this is the case. But, if you drive a high performance car, and you intend to keep it for several years, and maybe do the odd “track day”, then you need a genuine Ester/PAO (Poly Alpha Olefin) synthetic oil.

This oil costs more money to buy, because it costs a lot of money to make, very simply, you always get what you pay for!


unquote...

After reading this, aren't we tempted to use ester based oil ?

there are two brands I found, Silkolene Pro and the Motul 300V range

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'97 carrera S 100% original

944CS

this is not true


So does What does shearing do to your oil and engine in the long term?

When the oil film is sheared or squeezed out, then your protection is now reliant on barrier lubricant additives. Oil has 3 states of lubrication , Hydrodynamic, mixed film, and boundary(barrier). The best is Hydrodynamic which is nothing more than a flow of oil separating two mating surfaces. After a period of time shearing, the oil will lose it's ability to hold up to the same flow as before since the VI Improvers are breaking down causing the oil to thin down in grade. Once this happens, there is less film strength between the mating surfaces so it doesn't take as much for the oil to shear, therefore creating more heat which attacks the base oil even more and then starts to cause the oil to thicken up due to the excessive levels of heat and the broken down VI Improvers become a contaminant which added to the existing oil will continue to thicken and ultimately cause sludge if not changed in a reasonable time..

The higher the spread between the bottom number and the top number the more VI improvers are relied on for maintaining the viscosity. Better to keep the numbers closer.

All base oils film strength will shear under stress or pressure. The real way to help prevent wear is to maintain higher levels of antiwear additives This in conjunction with a good base stock which resists breakdown to high heat.

as read from bobistheoilguy.com