When To Change Oil

[donv]

There is (or at least was) an incentive for car companies to set longer oil change intervals, from the EPA or similar forces in governments everywhere. Back when we had effective CAFE regulations and the like, there was great pressure to reduce the amount of not just gas but also oil consumed. An easy way to do this was lengthen change intervals. The same folks that figured out it was cheaper to not fix the Pinto gas tank problem probably also were able to model when the engine would fail, on average, at change interval x+y%, so the car company execs could please the EPA. I'm sure it was/is targeted to be at some comfortable point past the factory warrany period.

I experienced this the hard way with my first "bought new" car... an '84 Honda CRX. Factory change interval (just extended at the time) on that was said to be 5K miles (conventional oil). I had previously always changed at 3K on all the used cars I'd owned before, with good long engine life. Following the 5K on the Honda got me a smoker by the time it hit ~70K miles.

I'm back to a religious 3K interval on my conventional oil cars since and they've all lasted well past 100K with no oil consumption. I'm doing every 10K or min. yearly on the Boxster with M1. With the oil being recycled now, I'm not worried that I'm ruining the planet with this practice - quite the opposite. By having the car last longer, that is one less vehicle that needs to be made as long as it lasts, saving energy and other resources consumed in the mfg. process. And of course, fewer steep new car depreciation cycles for my wallet, too.

[Brucelee]

Conventional DINO oil IS shot at 3K.

I use M1 in my wife's Subaru and change it at 5K.

Seems to work fine.

Originally Posted by donv

There is (or at least was) an incentive for car companies to set longer oil change intervals, from the EPA or similar forces in governments everywhere. Back when we had effective CAFE regulations and the like, there was great pressure to reduce the amount of not just gas but also oil consumed. An easy way to do this was lengthen change intervals. The same folks that figured out it was cheaper to not fix the Pinto gas tank problem probably also were able to model when the engine would fail, on average, at change interval x+y%, so the car company execs could please the EPA. I'm sure it was/is targeted to be at some comfortable point past the factory warrany period.

I experienced this the hard way with my first "bought new" car... an '84 Honda CRX. Factory change interval (just extended at the time) on that was said to be 5K miles (conventional oil). I had previously always changed at 3K on all the used cars I'd owned before, with good long engine life. Following the 5K on the Honda got me a smoker by the time it hit ~70K miles.

I'm back to a religious 3K interval on my conventional oil cars since and they've all lasted well past 100K with no oil consumption. I'm doing every 10K or min. yearly on the Boxster with M1. With the oil being recycled now, I'm not worried that I'm ruining the planet with this practice - quite the opposite. By having the car last longer, that is one less vehicle that needs to be made as long as it lasts, saving energy and other resources consumed in the mfg. process. And of course, fewer steep new car depreciation cycles for my wallet, too.

[MNBoxster]

Hi,

There is some pretty good evidence that changing the oil at the 3k mi. interval actually increases wear to the Engine and it's internals.

I know this seems counter-intuitive, but Engine wear actually decreases as oil ages. This has been substantiated in testing conducted by Ford Motor Co., ConocoPhillips, and reported in SAE Technical Paper 2003-01-3119.

What this means is that compulsive oil changers are actually causing more engine wear than the people who let their engine's oil get some age on it.

To add some perspective to this, I agree with the 10k mi. or annual (if less than 10k mi.) oil and filter change. Additionally, most of the dirt and particles which pass thorugh your Air Filter end up in your oil. If you live in (or have driven extensively through) dusty areas, or use a K&N Type oiled Filter, you should shorten the change interval. Hope this helps...

Happy Motoring!...Jim'99

[Brucelee]

Jim 99 is dead on with his post.

I too have seen this research on engine wear right after an oil change.

[mjw930]

Regarding the factory run-in of the motors Yes, Porsche runs every motor on an engine dyno prior to installing it in a car. As for the number of miles, that's unknown but they do run it through a computerized "break-in" then make power pulls to confirm output. The oil is then drained and replenished when it's finally installed in a car.

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.

[Brucelee]

" generated in this test of around five minutes' duration."



With all due respect, the text reads like a PR piece from Porsche. Having seen the metal shavings from a 1000 mile oil change, I would keep doing them.

5 minutes? Give me a break!

[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.