Some comments on oil change frequency

Chatting with my independent P car mechanic on oil change intervals, he recommended change intervals of 7- 8 k and expressed the following thoughts: 1. If it was his car, cheap insurance etc. etc. etc. 2. Laughs at factory intervals as he says their only concern is to get thru warranty period. Long fluid change intervals (of all types) also help manufacturer meet EPA type targets on volume of fluid disposal. This helps to explain why manufacturers that don't offer a free maintenance period (like Porsche) are stretching intervals much like BMW has. 3. Drivers that take numerous short trips need to change more frequently (nothing new there) but, interestingly, the larger oil capacity of 911's can exacerbate this issue as it takes longer to bring a higher volume of oil up to temp sufficient to burn off the contaminants. If you mostly reach full temp on your trips then the large oil volume is more of an advantage than a hindrance. 4. Observed that he is now seeing a good number of later model BMW's disabled by sludge (oil / water mix in engine) that lose oil pressure due to long intervals. These cases are out of warranty and can sometimes be fixed by a few oil flushes but some are terminal. 5. An interesting theory is that cars that are now fittted with plastic valve covers (read: BMW) are seeing faster sludge formation as the water vapor condenses faster when the plastic engine parts cool in cooler weather. I'm not sure I fully understand the implications of this but in all metal engines the heat is retained and the whole motor cools down more ratably. I assume that in an in-line or V, the air in the motor is trapped directly under these fast cooling plastic parts thereby allowing the water to condense more quickly then settle at the bottom of the engine promoting sludge formation. He claimed that BMW agrees with this off the record. Bottom line - I doubt I will go 15k on changes, more like 8 or 9k. Hope this helps and is interesting to eveyone.

Upgrading to a 996 on Monday from a BeeM 330d - which is going over 20k between services, it just doesn't feel right and although the manufacturer says it is the above is really interesting. One question - getting a Porsche dealer to change the oil is kinda expensive, does getting it done by an independent mechanic invalidate the warranty in any way. If it's ok then I'll certainly be going for every 7.5k. Also I know this thread must have happened a million times, but is Mobil One the best choice? Interesting to see even Porsche have gone to 20k with the 997

Recently spoke with a certified porsche mechanic at a dealership who proposes that the reason my 2002 C2 burns oil at the rate of 1 quart every 600 miles, is because the oil is changed to often. Go figure??? I find that if I drive the car hard, which is more often then not,(4-5000 rpm range) I burn oil at the rate of 1 quart in 600 miles. If I take a trip running at fairly low rpm levels, I get about 1 quart in 1000 miles. Of all the vehicles that I have, my porsche is the worst as far as oil consumption. Why it even out does my old 1939 Ford 9N tractor! I use to be somewhat concerned about the oil consumption, but seeing no smoke, and the fact that the engine is very strong, I have sort of given up on the oil consumption issue. I think I will be changing my oil at 7500 mile intervals. Tom L 2002 C2

The best way to find out if the factory interval is right for your type of driving is to have the oil tested to see how it is holding up. A good place to have this done is at Blackstone Laboratories . I have had all of my cars oil tested there after changing it out at the factory interval, and found that the oil's physical properties were well within their specifications and that contaminants such as fuel, antifreeze or other insolubles were well within tolerances. Because of that, I have kept my oil change interval at 15K on the 996. Here are the things that the oil is tested for. The test is only $20 and will help you establish a solid baseline for the useful life of the engine oil in your car and for your driving situation.

For the past 7 years or so, I have rarely driven the mileage recommended for a change in the year's time that lapses between service intervals (assumes no other issues)....so I just go in on the anniversary date of the delivery of the vehicle and have it done (annual service, need it or not). The '99 got more mileage than the '04 does now, but I was at 7500 miles at year 1 and had it done then. Got a parts hauler now that I drive 2 days a week or so, and the mileage is even lower now on the C4S Cab. I'll just go in once a year for the annual service. As for the comment on saving money on epa regs and oil disposal, they charge those fees to the customer anyway. I'd think the service depts would want you to have more frequent oil changes (especially at $200 or more per pop!). But to each his/her own. I think if you drive the car often enough, you will hopefully recognize problems as they creep up. Common sense maintenance means getting things done when they are needed, not necessarily when a book tells you to. Just my two quarts, er, uh, cents.

I read a tech article in Excellence about a year ago on this subject and they insisted that the recommended 15k oil & filter is adequate. However, like most I feel that is too infrequent and at least change the oil at 7500 and leave the filter for the usual interval. The article specifically referenced that the filter does not filter the finer impurities until it has been in the system for a while. I also change the oil more frequently , 7500 m as well, in my M5 BMW, which is recommended 20k, and bought a reset tool for the car computer so it will not remind me constantly with a SES light. Will

My car gets fresh oil every 8,000 Kms, or for my American friends every 5,000 miles, My dealer thinks i nuts but hey I drive it hard..

A question for those of you that change your oil on your Porsche at 5K to 7.5K miles. Have you had your oil tested to see if it actually needs changing so frequently or is it one of those security blanket things, or because of urban legends? I can understand a yearly change because of moisture accumulation in low mileage engines, but I have not been able to find any empirical evidence that would support replacing the oil at such a short interval for engines that have an average duty cycle, especially synthetic oil.

I have zero evidence that the car needs it, but I'm used to feeling the oli with my fingers and smelling it. After 5 or 6k the smell is definitely different. That's not empirical by a long shot, but it takes only about an hour or two on a saturday afternoon and a 5 quart jug of Mobil one is not much more than 20 dollars at walmarket. The 50 bucks or so and the 2 hours I spend every few months make me feel better. I bought 10 filters on ebay a couple of years ago, along with the plug washers. My only problem is that the drain plug is getting a bit worn and i never remember that until i start changing it

I use amsoil 5/40 instead of mobil 1 in my 02 C2. I obtain the oil and have had musante motorsports in S windsor Ct do the changes for me. I am going 10K between changes. Seems like a good number. Not too long or short. The car uses about 1/2 to one quart over the 10K miles. I drove 25K miles last year, mostly hwy, commute is 60-75 miles day depending on where i am heading. I am very aware of trying to warm car up with easy driving for first several miles and also to not let idle at startup. I try to not use for short local drives without letting engine fully warm up. The car has been great, other then RMS, which just got the new seal about two weeks ago. This was the second repair. Car certified until 08/100K miles.

It doesn't feel right to me , Its not a security blanket thing for me, its the fact Oil can not be good after all those miles, I change it because I like the fact knowing its fresh oil. I don't care if its good or not, but it makes me feel like i am doing the right thing.

Despite the improvements in oil filters, it's hard for me to believe that after six months or around 6K miles, that the oil doesn't get dirty. Although I have no scientific basis to make this judgement, it nevertheless seems apparent to me that dirty oil does not have the same lubricating qualities as clean oil. Therefore it would seem prudent to change oil every six months or at a minimum of every 6K miles. Of course this recommendation would only apply to those who plan to keep their cars for a long time. If I were leasing and had no intention of buying the car at the end of the lease, I would abide by Porsche's recommended oil change intervals. But if I owned the car and intended to sell the car privately, I would consider changing the oil more frequently. This could be a great selling point to a perspective buyer, i.e., you not only met but exceeded Porsche's recommended oil service interval.

It's very soft metal. I went out after my last oil change and bought a new plug (about $3) and a new filter and gasket set. I put the plug in the box with the filter so that next time I'll remember (takes me 6 months to go 3k miles). I'm sure the plug will survive another extraction but not sure it will survive another insertion.

Orient is on target. Test the oil and then you can stop smelling and feeling for differences. The test also helps identify other problems with the engine (wear, poor air filtration...).

Perhaps it's time to recall the oil FAQ that has been floating around for a while: http://www.atis.net/oil_faq.html The data is probably a couple years old, but the main message that I get out of it is that synthetic oils last longer and less prone to break down. Somewhere else I read that it creates a better seal thereby reducing the amount of contaminants through the rings. I also concur that an oil test is the best way to find out how often you need to change the oil depending on your driving habits and environment. I am a bit surprised about the mentioning of sludge build up in BMWs due to plastic cam covers. Is this with conventional oil or synthetic oil? I have used synthetic oils for a while now, and I have never seen any evidence of sludge nor varnish build up in any of the engines. I have with other people's engines using conventional oils.

"Somewhere else I read that it creates a better seal thereby reducing the amount of contaminants through the rings." Actually, the synthetic oils are supposed to cause MORE seal leakage than the traditional oils, and that was my experience with my 928 S4. I've not had a problem using Mobil 1 in the 996, however. Scott

How many times is this debate going to go on? I think this guy has about the only really valid point on here. The rest is just opinions and conjecture:

A lot depends on the driving. Short trips, not warming up fully, letting car idle to warm up in the winter all deterioate the oil or add to contaminant (ie gas) Longg drives on hwy at reasonable rpms are the best. Tractor trailors go at least 20K between changes. The synthetic oils will not break down from a heat or wear standpoint, but if contaminants get in the oil, that is a different issue.

What's with everyone's car burning oil? Mine burns Nothing. It does give a distinctive stink from the engine area after driving it hard though, and have been through what 5 rms's, and a cam seal but otherwise consumption wise it has never eaten oil. My car is at 15k now about to do the change and I thought it would be maybe a little low? Nope. I think that people just don't break the car in right when the get it new and you get mass oil consumption. I know this for a fact with previous friends' cars- A cayanne turbo was the worst of the bunch- but that's what you get when you buy it and floor it from the get go, then wonder, why am I burning so much oil?

Yeah, seriously. The standard answer is that it's normal in a 911. But then how come some people don't burn oil? I drove the hell out of my C4 but I never burned more than about 1/2 qt every 10K miles!