BruceP

At lot of the time that seems to be the case. But the meltdowns and the refusal to substantiate claims always leave me a bit uncomfortable. I think he could probably be a very valuable resource, but I can't get past the attitude.

pongobaz

just to throw a little more oil on the fire (pun intended). Isn't this really irrelevant since the are literally dozens of oils (viscosities and brands) on the latest Porsche approved engine oil bulletin? I see 5W50 Mobil 1 listed as approved, and I don't see it mentioned where 0W40 is the "preferred" grade. I trust my tech who for the last 20 years builds & preps race engines along with maintaining dozens of street driven Porsches all day long and if he tells me to run 5W50 in the summer, I'm gonna listen to him.

Benjamin Choi

The 5w-50 is more viscous than 0w-40 at lower temps and higher temps.

Mobil 1 5w-50 and 0w-40 are both listed in Porsche's approved oils list.

What some of us are not understanding is 1999Porsche's "tenacity" in his claim that the 0w-40 is the inferior oil to the other oil weights listed:

And I quote:

"why would you use a lower quality oil like 0W40 when there are plenty of better oils on the Porsche approved list? Even if you have not seen enough evidence or opinions against the use of 0W40 to convince you, why would you risk using it when there are so many unanswered questions about it?"

He has no evidence to support his claims that 0w-40 is a lower quality oil than the other approved oils, again, listed on Porsches approved oils bulletin.

Tbred911

if your using the 0W-40 oil 1999Porsche is correct... it doesn't have the film strength of other oils... which for me since I use that oil means that on startup after 4 seconds I give the engine a quick blip 2-3 times to 2-3000 rpm to get things flowing in there... since the 0W40 is thinner it will move and lubricate faster with a little help... where as a 5W50... the film strength practically guarantees a film will be on the metal parts so you don't have to use it.... I think though the 0W40 oil makes the car faster because it allows variocam to come in sooner and has less friction than the 5W50 oil....

perryinva

OK, I'm not claiming to be a tribology god, but I've taken some courses on it, and I have to tell you, unless there is something very new here, there is little to no relationship between viscosity and film (shear) strength. That is drilled into your head early on because "common sense" tells you that it must be so....and it is not. To put it another way, why on earth would you think that going to a slower flowing oil automatically provides better protection? The clearances between bearing surfaces are designed to allow the correct film thickness to exist, for the viscosity designed for. What happens, is that the real world manufacturing may not yield the exact results of what the design is. I have never read anything regarding shear that leads me to believe that 0W-40 offers inferior protection to 5W-40. It really depends on your particular vehicles actual manufacturing tolerances.

The difference between the flowability of 0W vs 5W at 50F for is pretty small. Both are 40 weight at high temperatures so should behave the same. What pongobaz says is correct..if it's on the approved list and neither is specifiaclly listed as the more correct oil over the other, then use what you want. In the summer whether it is 0W or 5W is irrelevant..they both flow the same fro a cold start, provide the same protection and shear strength. On the track, under high temp, the 50 weight will be thicker than the 40. Period. I have yet to read about anyone having an oil analysis done on the 996 engines, where the amount of metals was compared between 2 grades over 5000 miles. That is the ONLY (non-destructive) way to prove wear, that I am aware of. What a thicker oil will do, and it is easily observed by anyone with a 996, is change the oil pressure at the measured sensor location. Cruise at 2500 RPM (with what I assume is 0W-40 in my car) with cold oil and you'll be at 5 bar...15 minutes later you're at 3.4 bar. I assume that if you run 5W-50, you will (should) see a higher pressure when warmed up. Is that better? Maybe, maybe not. Depends totally on where the sensor is measuring relative to the pump, and if that higher pressure means you are flowing less oil through the ports due to that higher viscosity. Less flow is normally bad. Oil provides cooling as much as lubrication. Unfortunately, I do not have the oil piping path memorized yet, so I connot comment on this.

Personally, I am VERY surprised that Porsche "recommends" such a wide range of viscosities...the majority of the autos I have owned over the last 20 years have been very specific for the duty use. They have determined the flow vs pressure vs shear fil balance (among others) and have tested for what is better. Many times they change as the engine matures and a better combinatiun is found, not usually do you see "pretty much any syntheic oil between 0W -50, as long as it's 10W or less" tha ti son the approved list. If there is anything NOT annecdotal pertaining to Mobil 1 0W-40 being inferior, everyone on this (and a bunch of other) board(s) would want to know ASAP, as it has definitely been list and targeted as the "new" preferred oil on many posts. Viscosity is only ONE component of an oils design, and without measured proof that one is superior over the other, then it is all conjecture and posturing, plain & simple. I'm sending my oil out this week. I supposedly have Mobil 1 0W-40, but the 30k was done at an indie about 2k miles ago, and unless a dealer or I put the oil in, then I can't assume anything.

Benjamin Choi

i like the post perry!

i just don't get why 1999porsche is so adamant about 0w-40 being an inferior oil.... especially to the 15w that he recommends over it which is not on porsche's current approved oils list.

Palting

He probably has caseloads of it, and is looking to unload it .

Tippy

perryinva - love the post.....bravo........best insight I have read on oils