This is all (mostly all) my opinion, but...

Extended service intervals (or no service intervals) are as much a marketing ploy as based on sound engineering.

Just reading a UK car mag the other day and the MINI Cooper came in for a real high rating by the public, even though it has build quality problems and other shortcomings. The reason? The public likes the "free" service during the warranty of the vehicle.

More and more car makers are both extending service intervals (or eliminating then altogether) and offering free scheduled maintenance in an attempt to soften the blow of higher car prices.

Car mags are contributing to this trend by praising or noting in a favorable tone cars (long termers) that have extended maint. intervals and commenting unfavorably on those cars that require early services.

OTOH, some used car buyers guides downgrade used cars that have received only recommended services at recommended service intervals, the feeling is these are too far apart and do not constitute good car maintenance. The recommendation is to find a used car that has received more frequent services.

Now, sure oils have improved. But the demands on oils have increased.

Studies show USA drivers are spending more time in their cars, commutes times are getting longer, commuting speeds are declining as well.

Engines run hotter (to help reduce emissions) and have to power more parasitic loads, fancier climate systems, etc. Rings have moved higher up on the piston closer to the combustion chamber again to reduce emissions. Engine speeds are going up to help peak HP output.

Many parts of the USA see elevated temperatures (and high levels of airborne particles (dust mainly from agri sources -- although I note it is estimated that by LA (the city) taking quite a bit of water from the Owens valley millions of dust every year are picked up by winds there from the now dry lake beds and this dust is carried far and wide, but not to LA..., and the central valley is finding big increases in air-borne particulate matter) and as a consequence should be considered harsher environments for vehicles and therefore require more frequent services.

I bought my Boxster in Merriam KS (just south/west of KC Mo). I bought my VW Golf TDi from a VW dealer right across the freeway from the Porsche dealer. The VW dealer posted a notice that VW considered the area to be worthy of more frequent services due to the climate/environmental conditions prevalent in the area. There was no comment from Porshce...

Are 5000 mile oil/filter services overkill? Perhaps, in my case because I drive quite a bit and car sees very few short hops.

I note however, that just the other day I changed the oil and noted quite a bit of moisture under the oil filler cap. Even my avoidance of short trips, and extending driving cycles where engine gets fully up to temperature still sees water accumulating under filler cap and this water can only come from the oil and the oil gets it from combustion blowby. (Engine does not show any signs of any coolant leaks nor head gasket leaks, so the water's not a sign of trouble.)

Ideally, I would like to have a good oil pressure gage and use it to note when its time to change the oil. That is, when the oil pressure changes because oil is no longer being routed through the filter, but around it, thus indicating the filter's full and ready to replace, along with the oil. Of course, I'd pay close attention to the oil pressure at other times and if I saw, for instance, oil pressure at hot idle lower and steadily lower by some amount, I'd assume oil contaminated enough with water and unburned fuel that its viscosity was compromised and change oil/filter even if filter wasn't full.

My car is my car and I'll service it as and when I see fit. Don't mean this to sound harsh or mean -- it is not intended to be.

Just my clumsy way of leading up to my point and that is your (that is anybody reading this) car is your car and you can -- of course -- service it as and when you see fit. At least you should attempt to stick with the *recommended* service intervals.

When I buy a car I plan on keeping the car a long time -- though of course sometimes, most of the time, I get rid of the car long before its time simply because I tire of a car or my needs/wants/desires change.

As a result of this initial intention to keep the car a long time, I try to follow an agressive service schedule -- at least an oil (and other vital fluids), oil filter, air filter schedule -- this helping me to feel confident that the car and its engine/drivetrain will still be in good shape should I actually stay with the car for a long time.

Given I change oil so frequently, synthetic oil may be overkill. However, I'm reluctant to change to non-synthetic oil.

Did read of a motorcycle rider in the UK that puts several thousand miles or more on his motorcycle every week (he's a courier) and he changes the engine oil every week and he uses not the expensive "motorcycle" oil but the cheaper "automobile" oil (quality brand but not synthetic and he uses the recommended viscosity/grade -- 10w-40 IIRC) and his motorcycle engines do not seem to suffer -- he's getting sometimes hundreds of thousands of miles out of his motorcycle engines -- IIRC one Honda VFR V4 went 800,000 miles! -- before retiring the motorcycle and buying a new one.

But I've gone this long using Mobil 1 0w-40 (though I've used Mobil 1 15w-50 and Mobil 5w-40 Truck/SUV oil and once Mobil 1 5w-40 oil the dealer used for an oil change), that I'm not about to change now.

Sincerely,

Macster.

 

OK, I get the "Its my football and I'll play with it how, and when, I want", that kind of goes without saying. I was simply asking the question to see what opinions are, not really as an attack or anything.

The main reason I ask the question is that, if you look at this from the standpoint of basic chemistry, it simply doesn't make sense to carry over conventional thinking from one to the other.....

Conventional oils are highly suseptable to oxidation and thermal breakdown. This thickens the oil, blocks the filter, and releases sulfides and free hydrocarbons which can then bond with metal surfaces and coat or corode them. In an engine, this is Nasty, Nasty, Nasty. This actually happens a lot faster than you might think, so the 3000 mile oil change was born. Even this isn't anything more than a line of compromise, a generally accepted "norm." In actuality, your filter probably became ineffective in half that time.

Fully synthetic motor oils like Mobil 1, on the other hand, are formulated with non-conventional, high-performance fluids. These fluids are FAR, FAR less suseptable to oxidation and thermal breakdown as they were designed to be so. They contain little or no sulfides or "loose" hydrocarbons to come out of suspension and bond to metal surfaces to cause problems. They provide FAR more stable viscosity at temprature, and react much faster when cold. This significantly reduces engine wear at startup - the point when 90% of the normal wear on the engine's critical surfaces occurs. Conventional "oil" thinking simply doesn't apply when using these fluids. It is like comparing paper to plastic.....they are materials so different that trying to compare them is almost silly.

Mobil recommends 15K or 1 year change intervals. So does Porsche. You can safely bet your pink slip that those published intervals are AT LEAST 20% more conservative than the validation data indicated.

We tend to be uncomfortable with change, especially when it flies in the face of what we have always been taught to understand. I just think that we "gearheads" tend to carry over conventional oil thinking to the synthetic oils, and it really doesn't apply. I would make an educated bet that 10K mile oil changes are probably in the neighborhood of 55-60% of what the actual test data would show the change interval needs to be, under normal driving conditions.

It's just really hard to get your arms around a number that's more than 3x what your used to believing is the right thing to do.......

 

Didn't want to quote your whole message... but I'll try to address the points as best I can..

I haven't checked in a while, but most if not all oil makers simply parrot to use whatever change intervals the car maker recommends.

I can understand why: No way an oil maker wants to be liable for any extended service problems by recommending oil change intervals beyond what the auto makers recommend. (Look at what Toyota's facing with all the sludged engines. Imagine an oil company having to foot that bill?)

While oils like Mobil 1 are less sensitive to breakdown from heat, they still have to deal with the byproducts of combustion chamber getting into the oil. (With the ever increasing desire to reduce engine friction ring packages with ever lower wall tension are being used which means more combustion products will get into the oil.)

From this contamination, oil will experience a viscosity loss -- thinning -- due to excessive amounts of unburned fuel and water contamination, which is not breakdown per se, but will lead to the same troubles nonetheless.

Anyhow, the unburned gasoline contains quite a bit of sulphur. This with water will form sulphuric acid. (Other components of the gas and air will combine to produce other acids as well.) Sure there are additive packages in the oil that combat this but I wonder for how long?

Side note: And how can one say 15,000 miles between oil changes be a good viable number for everyone? Many UK car mags note the differences between auto usage in the UK and especially in Germany vs. the USA. The differences in driving -- more high speed driving over there -- less congestion, more temperate climes, even higher octane (and lower sulphur content) gasolines available.

Anyhow, I believe with modern oils and engines most engine wear arises not from mechanical/metal to metal contact per se, which seldom occurs even for engines that aren't used very often, but from the acid that builds up in the oil.

These acids that form over time, if left in the engine long enough, will slowly but surely attack engine's internal components and of course dissolve or partially dissolve and thus weaken these components on their exposed surfaces.

Now exposed surfaces like the insides of the piston skirts are of little consequence but bearing surfaces, rings, piston and cylinder wall surfaces, etc., are of great consequence. These see abrasion not only from possible (though one hopes rare, very rare) metal to metal contact but also from the oil.

Oil film pressures are high - which is how a thin (less than 0.001" thick perhaps) wedge of oil can keep a crank main bearing and its surrounding bearing shell from making metal to metal contact at any RPM, let alone at elevated RPMs -- and oil at these high pressures will exert no little friction against the surfaces it comes in contact with. Oil friction is real, which is why more and more auto makers are recommending lighter and lighter oils. And why using too heavy an oil can actually cause oil temperatures to go up because the oil gains heat from the friction of its large molecules.

This friction will scrub/tear away material that is weakened by this acid action. Thus wear occurs, clearances increase, because of this.

The engine thus rots away by prolonged exposure to oil that has developed critical levels of acid that has overwhelmed the oil's additive package that is intended to neutralize this.

I'm not afraid of change. I'm afraid of extended oil schedule changes that every indication is that are driven more by marketing than prolonged engine longevity.

Sincerely,

Macster.

 

I've only had my 2000S for 36K miles but only one repair to date, throttle body $350.
The big expense with the car is the high cost of maintenance and replacement parts and labor.
But you have to understand that this is a small production German car that requires specialized labor.
Personally I see this car as not just a transportation but part of my "life style/entertaintment" budget.
I've met allot of people I never would have met, taken part of driving events most people who own sports cars will never attend, etc. Somehow I think once you have purchased one Pcar you will probably always have plans for another. At the momment I'm hard pressed to think of another car that would be a step up in the roadster department. I'd have to consider another category of sports car altogether and I'm not really thrilled about sitting in a tin top on a gorgeous day.

 

Macster, I guess we just come from different perspectives on this one.

I agree that you can't say that x miles is the right change interval for everyone, that's just common sense. How you drive, fuels used, type of miles driven, environmental conditions, engine condition, and a dozen other things affect that. Manufacturers just establish a base line which is reflective of "normal driving conditions", or an estimated average. What else could they be expected to do?

I think if you have that much unburned fuel residue blowing by your rings, and enough condensation or other water contamination in your oil, at 3000 mile intervals, then you have far more serious issues than an oil change will take care of. The friction argument you make is actually more of a case for the synthetic lubricants, since they are more viscosity stable. The surface tension of a synthetic oil (NOT a blend mind you) and an organic oil are quite different at a given viscosity. The synthetic fluid is "slicker." An old racers trick used to be to LOWER the oil pressure but increase the oil volume to maximize horsepower. Why? To reduce the drag you referred to.

Anyway, I'll agree to disagree. You could go on forever with this one. Cheers.

 

Doesn't Porsche recommend that the oil filter be replaced every 30,000 miles?

 

At a Parade tech session a factory rep said they tested a 996 turbo in the US on regular gas for 100,000 miles and never changed the oil or filter. A teardown discovered no issues.

 

The M96 motors, with locasil coatings, will out-last the older motors by a wide margin - if, as you note, they dont blow up first. But wait, dont panic. History says that someone with a major gripe tells 7-15 people, while people without one rarely mention it. So the "self selection bias" over-states the problem by 15:1. Good for fuel-air mixture, but little else.

Next, how much is a 911 rebuild? And how often do they occur? $5-10K Good for 75-100k miles? 993s need head work more frequently than that, all too often.

A new/rebuilt (factory) M96 motor is about $10,000 (not $5-7 as below, I dont believe). Those motors are, it appears, "better than new", sicne they have all the updates.

There's also lots of chatter about RMS failures as terrible things. Jeesh. Its a little oil leak.

Early cars had some high failure rates from slipped sleeves and porous blocks - both manufacturing defects. Most have been replaced. If they have gone 50-75k - they are probably never going to fail, except gradually due to old age.

Yes, its too bad that there have been intermediate shaft failures nad some valve train failures. But I wonder how many of those are due to harsh treatment and neglect, too.

Grant

 

First, its nice to see disagreement with civility - so often missing on forums. Kudos to both of you.

I thought I'd add a few comments on things that I read in both of your posts.

One was around synthetic being overkill given frequent oil changes. not so, especially on an M96 motor. Synthetic not only holds up better - but performs better from new. Specifically, its almost impossible for a dino oil to meet porsche's and ACEA A3s requirements for:

- good low temp flow
- good high temp stability
- high VI
- high shear strength

Unless the bas stock is exception one or more of these must be compromised. I wont get into the details - there are places to read up on lubrication technology ( like BITOG), but suffice it to say that only a fee synthetics balance all these well. ACEA A3 is quite a stringent standard, I have found.

Next, the SAE and API - referenced by all domestic manufacturers and most imports - clearly stipulates that drain intervals should be specified for both normal and severe service. They define both. You will find that pretty much anything you do -- except cruise the freeway at 60 mph fully warm, but not hot - is severe service. Every owners manual I have ever read says to half the drain interval for severe service. Yes, the Boxster manual says this.

Several manufacturers have had to eat their words. Both VW and Toyota got into big sludge problems due to extended drain intervals. They both had to cut back to 5000 miles for some motors and applications. TSBs exist for both. Toyota changes their going forward policy. VW has been more circumspect. Now i don't suggest we need to change our Mobil1 0W40 every 5k miles - but 7500 (1/2 the suggested interval) might be very reasonable.

Finally, additives deplete fairly linearly. So arguments about whether "X" or "Y" is the critical change interval miss the point. Over time oil will clean a little less well, foam a little more easily, and in the case of crummy oils with Viscosity Improvers added (I would not use one of these in the first place), they will maintain viscosity more poorly in the face of temperature changes.

Finally, you can change oil too late and have consequences. But you can't really change it too early. So on which side should you err?

Grant

 

Our engines have twice as much oil as an Audi or VW for about the same sized motor, so why shouldn't our change intervals be doubled?

 

Good question, and yea, maybe, except that ratio isnt true.

My Audi takes 8.3 qts. My 986 takes 9.25. Close enough for government work.

Not sure who you are replying to, but if it is mine, then I made points based on fractions of manufacturers' recommendations, and the proper drain interval ratio of normal to severe service usage. Porsche's normal recommendation is 15k. According to the API, ***and porsche*** (RTFM) for severe service, which we all incur, that should be 7,500. QED.

Large oil capacity is a good thing, as you point out. But it does not ameliorate all the ways oil deteriorates, either. Many, maybe.

Grant

 

Thanks for the compliment, I know what you mean.

Good point on the synthetic being overkill at short change intervals counter argument. Hadn't really thought about it from that perspective, only cost and breakdown, but as you say, synthetic holds up better and performs better from the start. I agree.

7500 miles as a "norm", or base, interval seems much more reasonable to me. This is actually the answer to what my original post was driving at.


I agree that you can't really change the oil too early from a "least evil" standpoint. My point was more that it just drives up the maintenance cost unnecessarily. If you drive a lot of miles per year, 5 changes per year verses 2 changes is quite a difference in cost at ~ $65 per change (if you do it yourself.)

Of course, if you drive your Boxster 5k miles per year, it really doesn't make much difference....

 

My wife's Audi TT takes less than 5, as does every VW I've ever owned or worked on. The Audi dealer also uses dino oil not M1 for the oil changes at 10,000 miles.

 

7.x and ~8.3 qts respectively. I've done it a million times. VW also has a fairly strict list of oils that meet its various (501, 502, 505 series) oil requirements. It may be Dino, but its VW 50x approved. And ACEA A3, which rulesout many dinos.

VW and audi have retracted their 10k mileage change for someof the turbo I4 motor applications (amazing that they can retract for one app and nto another, huh?) due to sludge build up. There is a TSB out. It may or may not cover your particular model, but I bet it might.

Grant