When To Change Oil

[MNBoxster]

Originally Posted by mjw930

...That would pretty much eliminate the need for a 1000 mile oil change.

BTW, if a motor doesn't make it's spec rated HP it's torn down to analyze why. Because of this continuing analysis they have very few motors that don't make the grade.

Here's a quote directly from the Porsche website:

The following hot test is the final step in the engine production process. The engines are first of all heated up to operating temperature and then subjected to a functional test including full-throttle testing. Information in the form of up to 220 parameters is generated in this test of around five minutes' duration.

This ensures that Porsche's high quality standards are also met in the area of engine construction.

Hi,

You'll excuse me if I'm somwhat underwhelmed. Porsche may in fact run up their engines to confirm performance specs.

Too bad they don't also perform Quality and Durability tests, especially with respect to the RMS and Intermediate Shafts. These persistent Quality failures (prevelant through the entire 986, 996 model runs, with no apparent improvement through the years) are unconscionable for a Company with the past reputation for reliability. I mean, even Kia got this one right!

Happy Motoring!... Jim'99

[mjw930]

Originally Posted by MNBoxster

Hi,

You'll excuse me if I'm somwhat underwhelmed. Porsche may in fact run up their engines to confirm performance specs.

Too bad they don't also perform Quality and Durability tests, especially with respect to the RMS and Intermediate Shafts. These persistent Quality failures (prevelant through the entire 986, 996 model runs, with no apparent improvement through the years) are unconscionable for a Company with the past reputation for reliability. I mean, even Kia got this one right!

Happy Motoring!... Jim'99

Jim,

I'm not saying that they don't have their problems and I don't want to get into a pissing contest regarding Porsche's QC.

The question at hand was regarding factory specified oil change intervals and the discussion surrounding the factory's run-in proceedure. Here there can be no question, Porsche specifies the oil change intervals, including the initial change, based on their analysis of test data. If you choose to deviate from that formula then you do so at your own risk. As evidenced by some published scientific data more (sooner) is not always better.

I personally never bought into the 3000 mile change intervals. Those have been engrained on the population by the Jiffy Lubes of the world for the sole purpose of boosting their bottom line. No major engine manufacturer ever specified those intervals for normal driving conditions.

I think if you were to get access to the engineering data within Porsche you would find that even with the 15,000 oil change interval the oil's ability to protect the engine is well within spec. I wouldn't doubt if their data shows acceptable wear well past 20K intervals. Rest assured that they are not going to specify longer intervals at the risk of higher warranty claims.

Oh, and one more thing regarding the "5 minute" dyno runs. That is the portion of the run after the initial warm up phase that puts the engine through it's paces. On a modern computer controlled engine dyno you can properly break in an engine in a matter of minutes. Again, more is not always better.

[Brucelee]

"I personally never bought into the 3000 mile change intervals. Those have been engrained on the population by the Jiffy Lubes of the world for the sole purpose of boosting their bottom line. No major engine manufacturer ever specified those intervals for normal driving conditions."

Actually, the 3K change with DINO oil was not a bad thing. DINO oil performance drops off VERY QUICKLY as it wears, SYN does not. The hard analysis that I have seen on DINO would support the 3-5K changes with DINO, not SYN of course.

"I think if you were to get access to the engineering data within Porsche you would find that even with the 15,000 oil change interval the oil's ability to protect the engine is well within spec. I wouldn't doubt if their data shows acceptable wear well past 20K intervals. Rest assured that they are not going to specify longer intervals at the risk of higher warranty claims."

I have never seen data (even from AMSOIL) that would support 15 to 20 K changes UNLESS the oil filter was changed at about 12,500 or so.

M1 is pretty much shot at 11-12K without an oil filter change.

I would be ASTONISHED if Porsche had hard data that showed that m1 could run 20 K without an oil filter change and be up to snuff.

In fact, M1 extended perf oil is only claimed to be good to 15K. AMSOIL will guarantee 25K IF you change the filter about half way.


"Oh, and one more thing regarding the "5 minute" dyno runs. That is the portion of the run after the initial warm up phase that puts the engine through it's paces. On a modern computer controlled engine dyno you can properly break in an engine in a matter of minutes. Again, more is not always better."

I would love to see some back up for this statement. Break in has to do with bearings, metal to metal, and ring seating. How does the computer speed up that process?

I do think the "bashing" you refer to is valid. If Porsche specifies 20K on the oil, it would have more credibility if it had many less failures to explain.

PS- I love Porsche but am not blind to their blindness on certain issues.

[gRed04]

Originally Posted by Brucelee

"Oh, and one more thing regarding the "5 minute" dyno runs. That is the portion of the run after the initial warm up phase that puts the engine through it's paces. On a modern computer controlled engine dyno you can properly break in an engine in a matter of minutes. Again, more is not always better."

I would love to see some back up for this statement. Break in has to do with bearings, metal to metal, and ring seating. How does the computer speed up that process?

I do think the "bashing" you refer to is valid. If Porsche specifies 20K on the oil, it would have more credibility if it had many less failures to explain.

PS- I love Porsche but am not blind to their blindness on certain issues.

I think they mean a engine, out of the car, being dyno'd with a computer.

I have heard previously that the majority of any ill-fitting metal parts can be seated in a manner of mintues on a new engine. Not sure about 5 minutes but I read somewhere it happens pretty quick.

[Brucelee]

"I have heard previously that the majority of any ill-fitting metal parts can be seated in a manner of mintues on a new engine. Not sure about 5 minutes but I read somewhere it happens pretty quick."

This is an interesting angle of inquiry. I will play with Google and see if I can find more on the topic!

[mjw930]

Brucelee,

I'm not blind to them either I love Porsche cars, I bought my first one in 1977. I also know that they aren't perfect BUT, nothing else out there is either.

Oil issues on the car and motorcycle boards are almost like talking about religion, always heated and always many different opinions. No one wins in these discussions, trust me.

As for the computerized dyno break in, I'm referring to a computer controlled dyno. The Porsche engine dynos have some of the most rigorous and torturous models on the planet. They can do things to motors that we would never think of in the real world. They aren't the only manufacturer to have this level of sophistication but theye are the only one I have some first hand knowledge about. They have one model called the Stuttgart to Dusseldorf ( I think ) run. It's been known to break motors in less than 10 hours. For a motor's design to pass muster it must be able to be run in that simulation for over 500 hours none stop without failure.

Anyway, back to how you can break a motor in in 5 minutes. With modern metalurgy the only thing that really has to seat are the rings. There's no "wearing" of parts to match each other any more. Rings don't wear to the cyclinder walls, rod and crank journals don't wear the bearing surfaces and valves don't wear their seats as part of the break in (of course those parts wear but not as a function of break in). All that really occurs is the rings wear to match the ring lands in the pistons (i.e. seating the rings). This is required so they don't bind but still seal properly (hot exhaust gasses actually must pass over the top of the ring and into the land to push the ring tight up against the cylinder). If the ring is not properly seated in the land that process can't occur and you end up with all kinds of problems, the most notable ones being blow by and oil consumption. The single biggest thing that does damage during an engine's break in is heat. The maximum heat, heat cycles and average heat must be maintained within a certain range to prevent damage and allow the rings to seat properly. In addition, the force applied to the rings must be a combination of accleration (high top side pressure) and deceleration (high bottom side pressure) for them to work their way around in the land and seat properly. The break in and testing models that Porsche (and many other professional engine builders) use takes all of that into account. The first 5 minutes will make or break a motor, after that most of the dyno time is spent dialing in the fuel injection or carburation.

Don't trust me, go find a world class engine builder (not someone who rebuilds motors in the back of their shop, someone who builds competition motors in the top tier of their sport) and ask them if I'm right or wrong.

Now, when do I change my oil...... Since my P-Cars aren't typically daily drivers (anymore) and when they do get out they are driven fairly hard I follow a 5000 mile or 6 month interval schedule. The initial change is done at 5000 or 6 months also. If they were daily drivers I would still follow the 6 month rule but up the mileage to 7500. (so much for me following what Porsche says )

[Brucelee]

A very interesting site for actual test data on engine oil.


http://neptune.spacebears.com/cars/stories/mobil1.html

[Brucelee]

BTW-

For those determined to go 20K on an oil change I would suggest the following:

1-Start with either AMSOIL or M1 Extended Peformance oil-the 15 K stuff

2-Change the oil filter at 10K. Also make sure you use either OEM or M1 filter or similar long life filter.

If you do not need to add oil frequently during the 20K period (lucky for you), reconsider this whole 20K strategy!

As you know, I don't recommend the above but if you are determined, the above should keep you in good stead!