minuit997

I just changed the oil a week ago and stupidly forgot to use the oil analysis kit that I’m now intending to do at every change. How long should I drive the car before changing it again to give a meaningful sample? My normal oil change interval to keep results consistent?

BillB128

Keeping the normal interval makes the most sense to me. That way you get an accurate baseline going forward.

Bruce In Philly

2009 C2S 194K miles

How many miles a year do you drive and how many miles between changes? If you put few miles on your car, then every change, otherwise you will be waiting years for any trend. Less often or you will tossing money away IMO. I do it ... oh I dunno... every two years? every 1.5 years? I do it when I need entertainment.

.1 more often.... .2 not often as it really does not need it. For a .2, I think there was only one person here who learned anything and that was ID'ng a bad injector and they had other symptoms too.

This is a good question as I never thought that hard about it.... come to think about it, if I had a .1, I would do it every oil change and be doing frequent oil changes as I had two of these engines blow.

Peace
Bruce in Philly (now Atlanta)

minuit997

.1 with 70k miles and I drive it maybe 7500 miles a year. Am switching to Driven oil next oil change and adding magnetic filter and plug. The bore scoring threads have made me worried. But it’s showing no signs. No ticking or smoke or extra carbon on the exhaust. Because it’s a .1 I change every 3000 or so (roughly six months).

MrMoose

I've never done regular oil analyses on any car I've owned. Not really sure of the point: I've never heard of any significant difference between high-quality oils. And if oil analysis does show a big issue all of a sudden, what exactly are you going to do? Pre-emptively tear down the engine?

My advice is to just use oil that meets the A40 spec with some sort of a reasonable oil change interval and think about it less.

Aubergine 73

Bore scoring and potentially deteriorating engine condition is the reason to do it

Petza914

Based on 7,500-8,000 miles per year, make your change interval 4,000 miles and go that far on this oil before submitting your first sample.

steveP911

Oh. Can't figure out why anyone would skip a regular UOA, especially when their car is a not so cheap Porsche. Do you get a blood test during your annual physical? I do, because like the results from a UOA, it can tell you what you should be doing differently or what you should be prepared for. Changing from an A40 additive-limited Mobil One to something more appropriate for a 15 to 20 year-old car is one outcome. Having your fuel injectors cleaned and spray tested is another if there are signs of fuel dilution. Using a periodic injector cleaner additive to your tank. Much can be done short of tearing down the engine. Many others here far more competent than me to attest to why a UOA is valuable. The firm I use - SpeeDiagnostix - keeps track of your past UOA's on the sheet so you (and they) can see any trends of concern.

Were you really serious?

Petza914

Lots of reasons:

1. will alert you to potential intake system leaks if silicon values increase or that you're air filter needs to be changed
2. looking at viscosity numbers, TAN & TBN values, and metal wear numbers, you can determine what the appropriate oil change interval for that particular engine driven the way it's driven in. For example, on my supercharged 997 that's driven harder than my wife's car, my UOA reports on that one look very similar at 4,000 miles to what hers looks like at 5,000 miles, On my car I do 3,000 mile changes (never more than 4,000) and on hers I do 4,000 mile intervals (never more than 5,000).
3. Can tell you whether the oil you're using is doing a good job at protecting various parts of the engine. For example, Mobil 1 and Liqui-Moly have higher copper and lead wear than Driven which means the bearings are wearing more with that oil than with Driven oil.
4. These engines don't have a lot of iron in them so if you see a spike in iron content, it's probably the ball bearings in the IMS and you need to replace it before failure that makes the rebuild much more expensive.
5. Also can pick up coolant content to show if there's a head gasket or oil cooler problem.
6. Fuel dilution so you can see if an injector is leaking or not spraying properly. Fuel dilution is very dangerous as it prevents the oil from protecting the cylinder walls which then results in bore scoring.

I do UOA reports on every oil change from 7 Porsches, an Audi Q5, a GMC pickup, and my wakeboat so I can see what's going on inside the engines and if I have a problem I can address before it results in engine damage.

silver_tt

Spot on. My father and I always joke about how UOA and blood tests (he is a health nut) are basically the same.....

BHMav8r

997.1 82,xxx miles here, change oil every 5,000 miles and send in a sample. Used to do it every 10,000 miles, but as the mileage gets higher . . .

MrMoose

Look, if it makes you happy, go for it. But I stand by my statement that it's unnecessary.

You're not racing F1, these are just normal cars. They're rather nice cars, but still just cars. Yes, your engine is going to wear, but none of these cars are going to end up in a museum and playing in the noise of iron wear rate data or whatever isn't necessary. You use an oil that meets the specs and do regular maintenance and your car is probably going to be fine. And if it isn't and something fails I sincerely doubt that not using Driven instead of A40 or changing the oil every 6K instead of 4K is the reason. The majority of folks out there probably treat their cars like crap, lol.

There's this weird duality here between "Porsches are the best engineered cars ever made!" and "If you even look at a Porsche funny or don't use magic motor oil it will explode!". When you work on your own cars a lot you learn the truth is somewhere in the middle.

Anyway, drive more, analyze less is my advice.

Aubergine 73

You’re just going to totally ignore the bore scoring issue?

Petza914

Your car - you can do whatever you want with it, obviously. Since I keep every car I've ever bought until my son is going to take them over in 30 years, anything I can to do mitigate internal engine wear I'm going to do so Ihe and can enjoy them for decades, If 9 ppm of metal wear is fine, then 3 ppm is 3x as fine and the engine will go 3x as far before it has a wear issue.

If a better lubricant with more film strength keeps the pistons away from thy cylinder walls so scoring never starts, that's better than the alternative.

MrMoose

Pretty much, yeah: I think it's overhyped and not fully understood, and that people are kidding themselves if they think that even a once a year oil analysis is going to catch that in time to do something about it. If it scores it scores and then you're pretty screwed.

If you're worried about fuel wash causing scoring you'd be better served by just checking your fuel trims once a month or something. Again, that once-a-year oil analysis isn't going to catch it in time. As for me I just use A40 oil, good gas, let it warm up before I flog it, and throw in a bottle of Techron now and again.

So, yeah, that's exactly what I mean by playing in the measurement noise. As for me, even my daily only does like 5-6K a year, my other cars do like 2K. Thirty years on my Porsche is, what, 150-180K? I'm pretty confident most modern engines can make it to that with any oil that meets factory specs if you just change it regularly and stay on top of the maintenance.

Hell, even my '91 Alfa has 130K on it, has never had any internal work, and still has good compression and low oil consumption. I assure you I'm not using any magic oil, just Mobil1. You really think a modern Porsche with better tolerances, materials, and design is going to do worse?