boomboomthump

I knew this thread was going to go sideways as soon as someone mentioned their oil viscosity du jour.

Since this has already gone there... there is nothing wrong with 5w50 oil. It is a 50W oil at operating temperature. It is 5w when completely cold. Your motor is most at risk during start up when your is ask thick as maple syrup. Arguing that you should have higher viscosity oil at start up is nonsensical (5w50 vs 20w50). If you live in warm temperatures year round, sure maybe you don't care. If you don't, there is no question there is benefit in the first few seconds and minutes of start-up and oil warming that it takes for your 5w startup viscosity to reach 20w and then 50w at operating temperature. This has to be one of the most grossly misrepresented topics around.

Lastly, I'll add (since someone is sure to quote the owner's manual). Oil viscosity ranges 25years ago did not have a very large spread. 10w40, 20w50 had 30w spreads between startup and operating viscosities. Technological advancements have been made to increase those weight ranges to 35, 40, 45 and even greater spreads. So if your car normally needs "50w" oil at operating temperature and you can find 5w50 oil of course there are cold start benefits over 20w50 oil. You don't need to continue to use oil spec'd on availability decades ago. You certainly can continue to do so. But again, this argument over the "starting" or "cold" weight is illogical.

Holger3.2

... did somebody mentioned already the 'needed' zinc contend ...

nothingbutgt3

0w40 and 5w50 synthetic oils have the same operating conditions at cold starts, and so does the 5w50, which has an higher hot viscosity, and so I prefer to use this one, because it has a bit higher lubricant stability when overcoming the 90°C temperature, which happens while driving the car on the track for time attack sessions (I am very careful and I cool down any time the situation asks to do it).
I never used the 10w50 and 10w60 so far, because it can happen that one or two times I can take the car out from the garage, and start it at night exiting from a restaurant when it is maybe 0 degrees, and for this reason the 5w will be the right choice on the silver 993, which later on, when the limoncella will be ready, will be used only for road, more versatile situations, while the yellow will have the 10w50 or the 10w60 because she will never experience a cold start situations where temperatures are below zero, but only track day situations.

it is not when I take the car out from the garage to worry me, since in the garage temp is never below 10°C, but it is when using the car for meeting with friends, parking the car outside in the cold, with temp might be 1 or 2 grades below 0, who knows.
The 5w is good also in this situations, while the 10w I don't think is adviceable to try the luck.

Quadcammer

Interesting. So the fact that air cooled cars run a much larger p/w clearance than water cooled stuff wouldnt have any impact on cold viscosity choice?

Next up, you think oil actually transitions from a 5w to a 20 and then to a 50? you realize, i hope that oil doesnt get thicker as it warms and that there are different scales, hence the w for winter

Perhaps you shouldnt comment going forward about what is a misrepresentation

abiazis

What is TRULY amazing is that I paid $200 to have my oil changed in 1999 and still pay the same $200 in 2020 at quality indy shops..........the one ongoing annual maintenance service that has not increased for 20 years!!

I have lived in Georgia, NC, Maryland and New Jersey and used multiple garages for service.......

Edward

OK, here goes ...need I remind folks that this is a well-worn subject and there is lots in the archives on this; not to mention read up to one's heart's content. So I'll just throw in a few reminders, if I may:

1. The 993 and its engine design --and thus, tolerances-- were executed these many decades ago. This is indisputable and short of a rebuild using different --tighter perhaps?-- tolerances, the old flat six is engineered for the expansion/contraction of the air-cool medium and overall operating parameters. Use a thinner viscosity if you like, that's personal prerogative. But to opine using "modern data" without considering original build specification is not entirely the best method for drawing conclusions.

2. That cold start is essential to consider as the internals are at their most vulnerable. Given the aircooled engine's tolerances (eg. bearings, p/c, rings, entire valvetrain, etc.) are "baked in" with consideration of the oil of "that day," why one thinks they can infuse "opinion" into the equation of design parameters is genuinely beyond me. I am not arguing that one uses 30-year-old oil; I am simply arguing viscosity, as one additional design element, is an integral part of the entire "system" if you will. And this not only for the engine, but for the trans/diff as well. Anyone gonna put in a light-weight trans oil because today's oil is so much better?!! And indisputably, today's oil is far better than yesteryear's dino fill. I am arguing viscosity in this regard. If you like 0w or 5w for the engine under your own rationale, by all means apply the same logic to your trans and diff. Or will you really?

3. Back to cold startup, it's not only the oil's "hot" viscosity that is important but also its film left on all those aforementioned internals that are stone cold and static. The heavier "film" --for lack of a better term-- is what these air-cooled engines need to mitigate wear at this cold-start state where oil flow is nil. Again, if one feels good about running a light-weight oil at this cold state --again, where tolerances are designed for a higher weight-- then go at it.

4. All here can read and study on this subject on their own, clearly, drawing your own conclusions that make you feel good. I chose not only to do my own reading, but also heed the pro wrenches that have been at this air-cooled engine thing for decades, who have seen the guts of these particular beasts for decades, and all together, I draw my own conclusions.

5. And as an anecdotal piece, I will add that a year ago when my car was getting worked on (timing chain cover seals) and my shop did the oil change (where I have done every single oil change since 2001), he put in the "good stuff" which IIRC was a maybe a Redline 5w-something synthetic that he swears by (as his shop works on plenty of F-cars, current P-cars, and my lowly 993 was the "cheapest" in the shop, lol ...but he's a good guy and I like him). That said, that "good stuff" ended up with my oil-press light flashing intermittently at idle, and would go away as soon as I applied throttle! I turned right around, like never even got home and went bee-line back. He said, hmm, ok, I'll change it to a 10w (the expensive Castrol synthetic that he uses on "older" F-cars according to him). OK, so that solved my oil-press blinky light. But this absolutely confirmed all of my thoughts about this air-cooled design being a different animal entirely. And this on my 176k mile 993 that has never had its engine opened beyond valve covers, and uses approx 1qt oil per 2500 miles or so. And this with my car avidly tracked the first 3-4 years of ownership, in SoCal where 100+ degree temps at the track are norms in the summer, and my car neither melted nor even blinked hard.

Just sayin ...do as you will, all. I know what I'm doing

Edward

sdm100

15-50w Mobil 1 no issues also good for the seals

fsa

Slippery and well worn...always when the word "oil" appears in a thread.
Steve Weiner- on record multiple times here that our air cooled, dry sump engines should not have oil lower than 10-viscosity- unless or if operating in extremely cold environments.
Rothsport- uses 15-40 in my car. Cars heavily tracked or raced may require different spreads of viscosity.

Quadcammer

Another thing to note is that many oils with a spread of 40 or more from winter to operating temp utilize friction modifiers. This can result in the oil shearing out of grade quickly, as can happen with 0w40. So there is nothing wrong with using "old tech" oils with a small spread if it works for your application, as a 15w50 does with ours

BobbyT

nothingbutgt3:

Gbos1's avatar is one of the reasons I hang around this forum--it brings some sunshine into my day, and to those who rely on visual aids, it helps define the importance of model differentiation, specifically as it applies to the S. It is a rennlist icon, and the poster is a person of wisdom and taste.

stevensivak

What does the manual say?

Gbos1

nothingbutgt3

Oh man, seriously? Do I really have to say I was kidding?

​​​​​I wasn't criticizing his avatar, but the crazy world we are living in, a world, the USA I don't know way are Champs in that, but these obscure time is arriving here in Italy as well, where such images are considered assaulting, when they are just the expression of our own and legit taste.

No, we will be available to express ourselves only if the way we use is considered decent by someone invisible, that if we do other, will erase us.

​​​​​I hope you understand I like Gbos picture almost more for going against such cow style way of thinking instead of for the picture itself... probably Gbos chose it for many other reason than this, but thank you to the Gbos that put nice bottoms in face of the possible present women and omosexuals. (without any kind of second meaning)

BobbyT

nothingbutgt3,

Sorry for misunderstanding. I join you in defense of our right to enjoy the finer things in life!

rdad993

This is from my '98 owners manual.