McCulla

We're having near record temps here in N. Florida. "Logic" leads me to wonder if I should be using a 5W-50 instead of my usual 0W-40 Mobil-1 in this weather. Daily driver, 25 mile round trip commute, 05 C2. What do you think? (I am a frequent oil changer, 2500 miles or so...so it's always fresh!) My car uses no oil between changes and I use the A/C, so it gets up to temp on my commute. The temp guage on the hottest day reads around 220. I know many of you live in areas that have temps that are routinely much hotter than we see here, so let me know what you do. Thanks!!

Macster

If you change the oil every 2500 miles I think the engine will be just fine with what you have in there.

But if you want to switch over to 5w-50 there's probably no harm. It is an approved oil.

In fact, I recently I switched the Turbo over to 5w-50 Mobil 1 and the Boxster got Mobil 1 0w-40 (but will get same oil as Turbo next oil change: don't ask... long story).

But both cars will (probably) run Mobil 1 5w-50 oil from here on out. Why? I don't know actually. But Mobil 1 5w-50 oil is an approved oil and well just seems 'better' somehow. And in my driving I often encounter high temps: 119F one late June a few years ago returning from Palo Alto and a Concourse and 118F last summer on I-40 from AZ TO CA and a few years ago in my Boxster in southern AZ when I encountered miles and miles (all day in fact) of 116F heat. In this case the coolant temp reached 226F and stayed there, the intake temp got to 135F and stayed there and I have no idea what the oil temp reached. But the engine suffered not one whit from the experience. Fresh (1K) Mobil 1 0w-40 oil.

As a side note, before I had this oil changed I drove from KC MO to Bend OR and in very hot temps and at high (ahem) speeds in some areas and even though the oil had (by the time I reached Bend) over 5K miles the engine was just fine even though I couldn't get the oil changed in Bend like I planned but instead after stopping at Eugene (for a folding bike) I finally got the oil changed at Niello Porsche in Sacramento.)

Might point out that I encounter cold temps as well... One year left CA on a nice and sunny day and spent the night in Flagstaff where nighttime temps dropped to 19F. Last late Nov. left CA in reasonably warm weather (hot in fact in the central valley) and a day later driving the Turbo through a blinding snowstorm on I-40 between Calico Corners and Santa Rosa (NM).

BTW, if you run with the A/C on chances are the engine runs cooler than it would if you ran with the A/C off. The A/C on turns on the radiator fans all the time and this tends to keep the engine's coolant temp a bit lower than it would be otherwise.

Sincerely,

Macster.

McCulla

Thanks Macster! That is reassuring. On a side note, I have read in a couple of places some suggestion that a bit higher viscosity (like going from 0W to 5W) could be somewhat protective of the original, more failure prone IMS bearing like the one that my car has. Honestly, I cannot remember what their rationale was.

mdrums

For hotter weather 0w40 is the same viscosity as 5w40. If you can find 5w50 Mobil 1 and it makes you feel better you can run that because this viscosity is appoved for your engine.

Porsche has very low recomend oil change intervals based off your driving habbits. For me personally they are too long. I change my oil more frequently because I track my car a lot. I'll go either 3-4 track days max and change the oil not matter what mileage I do on the street. If it is summer when I am not normally tracking the car and just doing street driving I'll go 5k max miles and change the oil.

The synthetic oil can take much higher temps and more of a beating than conventional non-sythentic oil.

Macster

While I do not know what the primary failure mode of the IMS bearing is I suspect that it is the failure of the seal. The seal is compromised not by the viscosity of the oil but by the level of contamination the oil has. When the engine is shut off the oil immediately begins to stratify/separate.

This is similar to what happens when one stops shaking a bottle of vinegar and oil.

Anyhow, every bit of oil, from a puddle to that in the oil sump/tank does this separation.

At some point where the percentage of water is highest the corrosive effects of this water and its build up of acidic compounds will be highest.

What this can mean is if oil puddles and partially or completely submerges the IMS bearing seal the seal gets attacked by acid wherever this layer of acid water is concentrated.

Over time this compromises the seal to the point it lets oil in and this washes the grease out and in this case -- if I'm right of course -- the oil's viscosity plays I believe a minor role.

Sincerely,

Macster.

jhbrennan

Central Texas - still using Mobil 1 0W-40 - no oil consumption and oil temps are just fine.

McCulla

Thanks Macster! That explanation sounds completely plausible. I'm pretty certain that what I have read is that the failure is indeed preceeded by the seal failure. I'm not wishing myself any ill, but I cut open my filter on every oil change and delude myself into believing that if I don't see any obvious metal filings/fragments that I am still OK. Fortunately, I come down on the side of this issue being of small enough likelihood that I'm not worried about it. The best thing to know, for me, is that there is an apparently well thought out replacement/upgrade if I were to need it.

DGrayling

Some engine rebuilders have observed etching of 911 crankshaft journals from acid in the oil . . . another plus for frequent oil changes.

Macster

Over the last couple of years it has become my belief (though to some it may be common knowledge or pure hokum) that the majority of engine wear is not from metal to metal contact (except in cases of oil, oil system, or cooling system failure) but instead from corrosion.

The oil becomes corrosive and this eats away the metal matrix and over time the violence of the oil tears away tiny particles of metal.

It is like one were to walk up to say an exposed boulder and rub his hand over the thing. His hand's relatively soft skin will remove some of the material from the boulder this material's grip on the material under it, next to it, weakened by the corrosive effects of the air and rain water.

Thus my belief is that reasonably frequent oil changes keep the corrosive effects of the oil low and this corrosive wear is much reduced, enough so that the wear is pretty much nil.

Sincerely,

Macster.

NAM VET

While no fluid engineer, I have been interested in engine oiling for over four decades, and have some experience in various sports cars re: temps and pressures. Oil pressure is a function of flow volume/flow resistance. On my previous car, a race prepped Superformance Cobra, with a bored/stroked Windsor, i had two oil temp gages, and used various oil pumps and oil viscosities. I found that 10-40 gave me higher oil pressure and slightly lower temps than thicker 20-50, Redline oil. At some point, the relief valve shunts excessive pressure away from the engine anyway. On my 997C1S, I have 4+ bars at cruise, hot oil, so see no need for a higher viscosity than the 10-40. I have not run any 20-50 yet, and perhaps it would give a lower pressure, per my previous experience in other motors. Getting my first change tomorrow, about 5.5K miles on this fill, at about 18K miles. No consumption at all at this 5.5K duration. Can't comment on "corrosion", but my 997 has 9 quarts in the system, nearly twice most cars. So it can hold more contaminants anyway. But I'll stay with about 5K changes, plus I add a little Redline supplement too, to put the Mobil 1 to about 1500 parts of antiwear

Better to slowly hinder the cat's, than wear the cylinders.

I am going up to Hendrick in Charlotte, i want to see if there is a way to put a shift lite on the dash.

All the best.....

bdoviack

Unless you're tracking your car, I think changing your oil at 2500 miles may be excessive and possibly even causing more harm than good. Don't forget that after each oil change, you're essentially starting your car with no oil (until it gets put back into the filter, oil lines, etc.).

I spoke with Tony Callas (former lead mechanic for a few Porsche racing teams) and is now a technical contributor to "Excellence" Magazine and also has his own high-end Porsche shop (Callas Rennsport). He recommends every 5,000 miles with a good quality synthetic.

Don't forget the "gold standard" of 3,000 miles was done when engines were built and finished by hand and there was no synthetic oil. Today the technology has improved so much in both engines and lubricants that at 3,000 miles, the oil is still quite good.

I think frequent oil changes are a good thing but all in moderation. Brushing your teeth frequently is also good but if you did it 5 times a day, most of us would agree that is also a bit much.

Alan C.

NAM VET,

Do you use the Redline break in oil as you P/Zn additive?

As you, I'd rather stay with a 40 wt. max. I've read of a few people blending a 50/50 mix of Mobil 1 4T 10w40 motorcycle oil with Mobil 1 0w40. It would bump the P/Zn and have a little gentler cleaning package. Might be good for those that track a lot.

Where were you stationed?

McCulla

bdoviack, here is my token attempt to reduce the perceived harm done to my engine by changing the oil every 2500 miles. First, I'm guessing that at least a very thin film of this expensive synthetic oil is on some of the internals after draining, because I always run the car to operating temp before I pull the plug. So in the 20 minutes or so that it takes to drain, I'm hoping that there is more oil film remaining on the stuff that needs lubrication than on cold start in the morning....(?) Second, I always fill the filter cannister before I replace the filter/cannister. Third, even though I don't know the path that the oil takes when I pour it into the filler neck, I assume it's touching something along it's way to the sump (??). Anyhow, I never get even a hint of clatter at start up, and my oil pressure guage goes up to approx 50-60% of the max reading (at idle) nearly instantly on start up. This may be completely delusional, but that works for me!

mdrums

If you run an oil that is thicker than what is recomended the Vario-Cam sytem in your engine could not properly operate.

Stick with 0w40, 5w40 or 5w50. I use the factory fill 0w40. I tried 2 oil changes of Castrol Syntec 5w50 last year and did not notice any difference in oil temps or pressure at the track.

NAM VET

Alan, was District Senior Advisor, ie, with one SFC on my team, Teams 80 and 84, Kien Phong and then AnXuyen Province, in IV Corps. In the latter, way down on that tiny hook at the end of the country, at the edge of the U Minh Forest, sometimes i was sure I was the southernmost American in the whole country. '71-'72. Son, my interpreter was in the chopper than in '68 picked up Nick Roe, the author of "Five Years to Freedom", captured with later MOH Rocky Versace. Kahn, my other interpreter, stepped on a mine and blew his legs off. I still speak some Vietnamese. My picture is with a full auto M2 Carbine, along the edge of the U Minh.

Tour was a year, did 366 days in country, as '72 was leap year, hence the extra day. Chose to spend my whole year out in the field, as I could live on ten bucks a month, no R&R, as I was then carrying a slide rule and chemistry book in my rucksack, doing chemistry problems out in the field, intending to use my GI bill for medical school. Sit on a mud berm, M16 in my lap, working out problems. Later, back in the "land of the big PX", was CO, A/1/5, Fifth SF, for 18 months, with further worldwide adventures. Was Desert Storm, too, Chief of Staff of a very busy hospital 300 miles out in the desert. I fly my Flag every day, in honor and memory of my friends in SEA who never came back. My best friend went missing, they never did recover him.

Had my oil changed at Hendrick in Charlotte today. Mobil 1 0-40. I'll add about three oz of Redline supplment. Bring the Zinc/Phosporus up to about 1500 or so. I ran Redline always in my Cobra. Talked with the service manager, he is an old friend, we have tracked together. He has put in shift lites in some cars, a green/orange/red diode small thing, out of Australia. I had a shift lite in my Cobra, that way you can keep your eyes on the road and just catch the light blink for an upshift. Stay off the revlimiter that way. He discussed the first gear balkiness with the short shifter.

My tire warranty is putting a new rear Rosso on for me, had a nail this past weekend down at Charleston. A bit of a saga, that experience.

All the best...