sjfehr

I know nobody wants to see science or reason in a discussion about oil, but why would you think oil pressure within Porsche's recommended pressure range and using one of Porsche's recommended oils is a problem to be solved with higher viscosity oils? Do you understand what engine oil pressure actually represents and why it matters? Switching to a thicker oil because it's harder to push thicker oil through small holes may make your pressure read higher, but it isn't going to help push more oil through small holes.

Alexandrius

SCIENCE

Macster

Good point.

Oil pressure is important to a point but oil flow is just as important. Oil has to flow to the bearings and out again. All the pressure in the world won't be any good if the oil flow isn't there.

The bearing clearances are on the order of 0.001" or thereabouts. Thinner than a piece of paper is thick. Imagine. Just that thin a film of oil is able to resist the considerable forces from the crank and rods.

The oil has to flow in but also has to flow out just as readily as the oil absorbs heat from friction generated by the spinning of the bearing journal inclosed that thin film of oil. Too thick of an oil can deliver impressive oil pressure and miserable even engine threatening low oil flow volumes.

To those that worry about "1 bar" of hot oil oil pressure, you have to realize you are using a pretty crummy measuring tool. The oil gage in the car is not that accurate. It is pretty much designed to read ok, not too low, but not too high, all the time. Like the coolant temp gage. And as with coolant temperature the same with oil pressure. The time to worry is when the warning light comes on. 'course with oil by the time the light comes on generally the engine's toast. Thankfully these engines do not suffer from catastrophic loss of oil and oil pressure that often. The gage is there mainly for show.

Besides the oil pressure is measured at about the furtherest point from the oil pump. For my Boxster the oil pressure is taken at the lifter oil galley. 1 bar there is probably a bar or two more at the mains/rods.

For my Turbo engine the oil pressure sensor is also located a distance away from the oil pump but I can't find specifically where it is located. (I recall when talking over oil pressure and such with the techs they telling me the Turbo oil pressure sensor is likewise located at one of the camshaft covers and takes its reading from a lifter oil galley.)

Also, it is quite normal -- I'd be worried if it didn't happen -- for an engine to get quieter with fresh oil in it. I would notice this every time I changed the oil in my cars. Before the change listening to the engine idle then upon start up after the change with fresh oil noting how quiet the engine was -- even after letting the engine idle enough the oil was up to temperature which didn't take too long as the engine was of course hot when the new oil was poured in.

Like new tires quiets the car new oil really quiets the engine.

But with my cars after 5K miles with either 0w-40 or 5w-50 oil in the engine the engine is noisy again. Not scary noisy, just a bit more noisier than when the oil is fresh. Hot idle oil pressure is down but not much, just a needle's width or so down from what it was when the oil was fresh. There is some variation too depending upon the ambient temperature. The engine's operating temperature varies some, staying a bit lower in cooler temperatures while climbing some in hotter temperatures. And this affects oil pressure at "hot" idle.

Kind of funny but in another car forum to quiet noisy/clickity/clackity engines (the noise is primarily valve train noise) owners are switching to Mobil 1 0w-40 oil with possibly some guidance from the factory. The justification is the engine becomes quieter than with the original factory oil recommendation (IIRC 5w-20!) but also at some level because it is the oil Porsche recommends in its engines...

However I have no problem with a Porsche owner switching away from Mobil 1 0w-40 oil as long as weather conditions where he lives/drives doesn't require a 0w oil, -25C (-13F) or lower.

But -- as an aside -- I would think if temps are down to 0F 0w-40 is probably the preferred oil. However, I have to admit I did spend some time last winter in my 996 Turbo driving around in single digit temps with 5w-50 oil in the engine with the engine apparently suffering not one whit but I was quite mindful of the cold temperatures and the oil and let the engine idle a while before heading out and I kept RPMs down even when the engine was up to temperature. It would have been a bit more less stressful had 0w-40 been in the engine but I really didn't expect temperatures to be that cold where I was heading.

But barring weather conditions, extremely cold temps, if an owner wants to run a 5w-40 oil or even a 5w-50 oil -- as I have elected to do given where I live and (mostly) drive is quite mild in the winter -- seldom dropping to freezing let alone any lower -- and yet can see summer time high temps 100F or higher (107F to 111F for instance back in late June of 2009, shortly after I bought my car) -- I have no problem with that.

What I have a problem with, and really it is not my problem but the problem of the car owner who does this, is when one ventures away from an approved oil.

KLS

When I changed to Motul 5-40 from Mobile 0-40 the difference was significant. I wouldn't say it ran any cooler, quieter or smoother, but my confidence soared and isn't that about all a person can expect from a new oil?

jhbrennan

Confidence in what?

Lvt19672

Mobil one 0w-40 and motul xcess 5w-40 are both approved by Porsche for use in our vehicles, whichever you choose is up to you. It's great we have so many options.

Ericson38

Good points. Thick oil results in higher pressure at the pump output, but the mass flow rate is down, and therefore heat transfer is down. That, and the startup to build films in the journals will take longer.

For these comparisons, does MOTUL have a 0w-40 formulation, or are we comparing the two weights of two different motor oils? A thicker blend will quiet down an engine, like it does on our 428 CJ Ford with a solid 270S compcams grind, but I run 10W-30 in it (high zinc) instead of 20w-50 (high zinc), since we aren't racing it on the salt flats, and I don't want 90 psi at 3000 rpm. Flow and heat transfer is also important.

gpjli2

What I have a problem with, and really it is not my problem but the problem of the car owner who does this, is when one ventures away from an approved oil.[/QUOTE]

Just to be clear here there is a list of Porsche approved oils. I am not aware of anyone advocating the use of a non approved oil. Likewise there are numerous viscosity charts which show the there is no difference between a 0 and a 5 lower range until you reach -10 or less F (as you noted).

There is however a difference in the ability of a pure synthetic to maintain its viscosity in the extreme heat generated in an engine. This is probably more of a factor in keeping oil pressure high at running temps than "thick oil". Both oils start out with higher pressures upon startup. Motul shows less loss in oil pressure over a wider range of temps.

Excellence magazine has come out for Motul over Mobile time and again. You might better ask your dealer why he continues to use Mobil in the face of some pretty intensive research done by folks like Hartech and others. I'll wager there is a financial benefit reaped by the dealer to continue with Mobil.

As for folks on the board, there also seems to be more than a bit of resistance to change. There is a lot of information out there and I have done my homework. If others do not or decide it's not an issue worth investing time and $$ on, well it's their 9 nine quarts of oil.

Cheers.

Team Plutonium

LOL!

+1. This.

KLS

That my engine won't fail due to inadequate oil.

Alexandrius

just changed from pennzoil ultra ferrari and porsche approved euro formula 5w40 to regular old mobile 1 0w40 as recommeneded by porsche...

Engine failed, caused fire, burned own my garage.

Lesson learned dont change to mobile 1 ow40.

NAM VET

I have a different engine, the Mezgar, in my GT3. I just had the oil changed from the prior fill of 0-40 Mobil 1, to Redline 5-40. My car always pegs the pressure no matter what the oil or ambient temps, at anything over about 2.5 -3K RPM. But I did note a slight increase in my idle pressure, was 1.5 BAR, now nearly 2 BAR. I presume this is due to shear of the viscosity compared to the fresh Redline. A higher Idle oil pressure is not terribly important, as there is no load on the motor. Actually, I run a variety of Redline oils, which are ester based, in everything I have that has a gas engine. I have a source from a used NASCAR parts place up in NC, so not much more cost than other oils. I am of the opinion that all modern oils are superlative lubricants, and synthetics are even better.

Remember, Oil is cheap, engines are expensive.

All the best...

cvtbenhogan

Wow. Lots of forum feedback regarding oil pressure at idle and oil quality. Even a post from quadcammer.

As an update, warm bar at idle dropped to 2.75 yesterday after 2 hours of driving. New M1 had around 2.5 bar at idle and fell off from there to 1.5 after 3500 miles. I thought it was shearing of out grade.

The car seems to rev smoother with Motul and found the gauge slipping past 4k more often prior to shifts. I tend to rely on the added motor vibration/noise in the upper 3s to signal an up shift. Clearly not science and the oil is new. Will be interesting to see the blackstone test on Motul later on.

I've got no issues with M1 and will still use it in my other cars. That said, I don't think that M1 has kept pace with oil technology. It's price also seems to reflect this.

workhurts

Thanks for the reminder on he rebate and you were right, the rollback price is $23. Gonna buy another one today before the rebate runs out.

Lvt19672

Gotta love WallyWorld.