matt777

I think I was agreeing with that

dryadsdad

...and I'll do the change at winter lay up even though I'm sure it's not needed

Archilla

Quinn/CAT, the heavy equipment guys, also do oil analysis. Most of their business is commercial fleets of land moving equipment and such, but they'll test anything. I used to go with Stavelely as recommended by Charles Navarro, but I have a Quinn location close to me, so it is easy to pick up the kits. They are also a little cheaper than Staveley, their results come back sooner in my experiernce, and their analysis kits come with a prepaid mailer and the tube to draw the sample, so there is nothing else to worry about.

http://www.quinncompany.com/parts-se...fluid-analysis

I've done virgin samples of the same oil at both places and the results are consistent, so I think either is a good choice.

I'm no expert on oil, so I'd be curious to hear from Charles or Steve W on this, but there are so many variables in usage that I would assume that periodic oil samples are the best way to figure out what a comfortable change interval is for each person's use. High temperature use (i.e. track days, etc.) can accelerate deterioration of the oil, but infrequent use and/or short drives on a regular basis can contribute to water contamination from condensation, so I think whether you use mileage or time depends a lot on how the car is used. No one answer fits everyone. Porsche's long intervals probably make sense if you use full synth and drive the car on a daily basis and get the car fully up to temp every time, but cars that are tracked, garage queens that go out infrequently, or cars that only ever see short trips which don't get the car fully warm probably require different treatment.

FWIW, I change somewhere around 4k miles or 1 year, the car gets used weekly and sees a handful of track days per year. I've done a number of analysis samples on previous fills, and what I found (with the Brad Penn) is that after an initial drop in the TBN and viscosity, things stay pretty stable and don't drop off much until I change the oil. I've never seen deterioration of the TBN to the point that Charles would consider a problem, and that includes a lot of hard driving.

-Ruben

dryadsdad

@Ruben,

I don't think daily use makes any difference. It's usage type. an engine which isn't used regularly but when used it used in a light duty manner (longer trips but no racing) will demand larger oil change intervals.

Canyon56

Here's my most recent one (it's from my AMG, but people can get the idea)

Archilla

Maybe. Anyway, my point there was mainly regarding whether miles or time is the appropriate measure. 15k miles might make sense if the car is driven every day, but for some people here 15k miles might be 5 years worth of driving or more. In 5 or more years of light usage, I would definitely consider the impact of condensation in the sump tank on the oil condition, if for no reason other than seasonal temperature change, so time is probably a more important measure than miles for occasionally driven cars, regardless of usage type. For any kind of use, periodic oil analysis can answer a lot of questions about the condition of the oil for each particular person without speculation.

Regardless of how they are driven when they are run, very occasionally used engines tend to develop oil leaks and other issues as well. Forgetting about oil change intervals, engines used more frequently tend to be happier. Their owners too.


-Ruben

black ice

I can't answer the survey. 8^(

Change every 10K miles. Daily driver with 145K, using only 1qt between changes.


dave

IXLR8

Thanks! I'll print it out and see what comments I'll get from our labs.

I'm just surprised that the Blackstone Lab report does not list equipment used and its calibration date.

95 NC 993

5,000 miles or one year, whichever comes first. It doesn't seem excessive and it certainly isn't hurting anything with 'average' type driving.

dryadsdad

I think you have sound points about condensation in the sump, however I'm skeptical about the oil leaks on little used engines. Yes, they do develop leaks but an oil change won't make a difference. It's the museum car issue instead.

A car little used or not used (museum) dries out. All the seals shrink and this is what causes the leaks. Many folks bought the pristine examples when Harrah sold off its cars only to find they bought rolling junk - at least as far as running was concerned. They looked new (fresh resto) but they didn't run for squat. They had turned from automobiles into statues. Changing the oil would have made no difference. These are cars - they NEED to be used or they die.

I am all for periodic oil analysis. Given how much we put into these cars in care and money, this is VERY cheap to add.

Archilla

Yeah, we are saying the same thing. I was not speaking clearly if I gave the impression that I think oil changes will prevent oil leaks in garage queens. Cars driven infrequently will tend to develop leaks, and as a separate comment entirely, they will need oil changes based on time rather than mileage.

In any case, everyone looks at the same information (from Porsche, independent mechanics, and other owners) and comes to their own conclusion on what they feel comfortable with doing for oil change intervals.

These engines are pretty stout. As long as someone uses a good quality oil, chooses a reasonable interval based on their usage habits and changes both filters at the same time, and runs the engine regularly and properly, everything will be fine.

-Ruben

matt777

Why? Are you auditing them? What do you expect for $25?

dryadsdad

Now we can start a thread on what is 'good quality oil'

Ed Burdell

Looking at the sample Blackstone report, I take it we're primarily interested in the section labeled "Properties" when assessing how the oil is holding up?

dryadsdad

Thsi thread gave me an itch. I just scheduled an oil change for our 993....