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How often do you change your oil?

Started by michaeld, 31 March 2006, 10:44 PM

michaeld

Well, boys, it's that time of the year to change my oil (or is it?).

I've had the mantra, "every six months or 3,000 miles, whichever comes first" drummed into my head.  But usually I've at least reached the former milestone before the latter.  Nowadays I'm even hearing "every 3 months" bandied about.  Like many of you, I've had another (albeit less fun) "ride," and so my 450SEL has only racked up 2,100 miles in the last 6 months.  That and the fact that the 450SEL has a 50% larger oil capacity than anything I've ever owned as well as a more expensive filter has me wondering: when should I REALLY change my oil?

If my memory serves correctly (and, being that I are a genius it usually does ;)), the oil change interval in my factory owner's manual is 12,500 miles and at least once a year.  Was Mercedes smoking funny-weed back then?

I personally would NEVER let my girl go that many miles between changes, but howabouts that "at least once a year" part?

On the "change often" side, I hear that water vapors build up in the pan (particularly if your driving is characterized by short trips), and that frequent changes provide cheap insurance against engine-killing sludge build-up.  On the "poop on that silly notion" side, I hear that frequent oil changes are nothing more than the result of a marketing campaign on the part of oil companies and Quikie Lube stations, that oils are better made with more conditioners than previously, and that you are only wasting your time and money if you change oil so often.

So what side are you on?  How do you decide it's time to change the oil?

Denis

Hello gentlemen

Six months or 6000 km, whatever comes first using Mobil 1 synthetic and adding NOTHING ELSE :  no goblin elixir, no dragon breath , and certainly no PTFE products (clogs up the strainer on the oil pickup in the sump  :o

My engine is very, very clean and quiet : no varnish anywhere under the valve covers.

Rebuilding an engine (something I have done several times) is NOT my idea of enjoying a car.

I also believe that sustained high speeds are necessary for a healthy engine. I can always find a place where I can drive over 140 kph or more - BTW french roads are superb for this kind of thing and policemen NEVER work on sundays  8)

Denis

Paris, France

Des

I change oil and oil filters on my cars every 6 months, regardless if they have set in the shed and done 50k's or done 4,000-5,000k's

I also take any cars that are sitting around for a 10-20k spin once a month and operate all accessories to keep all the parts operational and working.

From experience and talking to friends and mechanics cars hate sitting around doing nothing as they do being driven under harse conditions.




michaeld

Well, gentlemen, my "problem" has been solved - at least this time around.  I brought my car in for an oil change, tire rotation, and alignment today.

It turns out I are NOT such a genius after all.  "When in doubt, consult the manual"; the manual actually says oil should be changed every 6,000 miles or six months (which is a little more realistic than 12,500 mi, isn't it?).  If you have subjected your car to hard driving, you should change it every 3,000 miles.  You can do everything according to spec and still have problems; you can put off doing any maintenance at all and not have any problems.  But why fool around and take chances?

I'm one of those, "Do what the manual says because they've got to know more than me" people.  But I've come across several people with mechanics-training who do NOT believe in frequent oil changes (particularly with synthetics).  They boast that they've been ruinning the same oil for 100,000 miles without mechanical breakdowns. 

I changed my oil on the theory that water condensation can build up over six months - regardless of how many miles you drive or how hard (or gently) you drive.  So even though I've had 2,100 mostly freeway miles I needed to change oil.  Does water condensation really build up in motor oil?  I have no idea; there doesn't seem to be the same problem with transmission fluid (or is there?).  When I (more carefully) read my owner's manual, it mentions 30,000 mile service intervals with no mention of any time intervals for transmission fluid.  So, does condensation really build up in motor oil, or is that just an "old mechanics" tale to get more work?  I really don't know, but I aint takin' no chances!






Denis

Well michaeld  and friends of the web

Quoteyou can put off doing any maintenance at all and not have any problems

...for the time being, :P

Engines process fuel into energy and create combustion by-products (acids, sulfur, etc...) and oil, any oil, is not going to "neutralize" that stuff. It just adds up into an exotic fluid product. If you had some kind of "separator", you might be able to filter Mobil 1 and use it another 10 000km...but there is no such chemical device on the market. And as if this not enough, there is the question of oil oxydation just by being in contact with air...

I am afraid that the "just drive it until it fails" idea is an American old-wives tale originating in the primitive, underworked cast iron V-8s of 40 years ago.

Denis

Paris, France

Captain Spalding

Greetings all,

I am a member of several car-related forums, and the issue of oil-change interval is always a hotly debated topic. What I have to say comes from a background in air-cooled Volkswagens. Aficionados of air-cooled VWs are in many ways less sophisticated than your average Benz owner, but, as air-cooled engines tend to put stresses on motor oil unlike those in any other motor, VW owners tend to be somewhat more sophisticated and even obsessive on the  topic of oil change intervals. Because the role of oil in temperature regulation is so much greater in air-cooled engines, they subject the oil to much wider ranges of temperature than do our beloved 116s, and the filtration system is downright neolithic by comparison (the "filter" consists of a stack of metal screens which are cleaned at each oil change.) Combined with the relatively short lifespan of VW motors (80-100k) air-cooled VW owners are rather fanatic about doing whatever it takes to increase the time-between-overhaul. A stock air-cooled VW motor is one of the few that, in practical terms, routinely demands a 3000 mile oil change.

The purpose of oil is three-fold. First, it is a lubricant. Second, it removes contaminants and combustion by-products and holds those too fine to be filtered in suspension, and third, it helps to carry heat away from the hottest parts of the engine. The detergent additives in the oil help the oil to hold the impurities in suspension and keep them from being deposited as sludge and varnish on various parts of the engine. In a properly maintained motor, and by that I mean one in which the proper amount of oil is maintained and which runs within the proper temperature range, oil should easily remain effective well beyond 3000 miles. The 3000 mile oil change should be reserved for situations of "severe" duty. That is, dusty climates, or where the majority of driving is short distance, where the oil doesn't get up to temperature long enough for the moisture accumulation to burn off. Extremely high temperatures can cause the oil to loose its lubricating properties, and the detergent additives to loose their ability to hold the impurities in suspension. Darkened oil is not necessarily a sign that the oil needs to be changed. It needs to be changed when it becomes saturated and can hold no more impurities in suspension. These impurities are not abrasive to the engine, but if they are not held in suspension, then sludge deposits begin to form.

So, when to change the oil then? It varies depending on the vehicle and driving conditions. I went the oil-analysis route. It cost me $90 to have 3 analyses done. The first was on virgin oil with zero miles on it, right out of the bottle - a baseline. Then one at 3000 miles. The results of that test indicated that the oil had plenty of life left. Then another analysis at 6000 miles. That analysis indicated that the oil was still performing as it should. The lab indicated that I could probably continue driving under similar conditions until 7500 miles with no undue wear, but stated that the manufacture recommendations, if less, should supercede their advice. So, in Southern California, with my particular mix of city and highway driving, I change my oil at 6000 miles.

Some other notes:

Oil analysis will show an increase in metal particles which can predict the failure of a bearing or other component, which allows for corrective action before more costly damage can occur.

Also, more and more I read that folks are using fluid evacuators to suck the old oil out through the dipstick tube. This is a bad idea, as it can leave sludge in the pan that would otherwise be removed by draining the oil out through the oil-pan drain hole.

Finally, most wear occurs in the motor between the time it is started and the time the oil reaches a temperature that allows it to be properly distributed through the motor. At least as important as proper oil change interval is allowing the car to sit at idle for a minute, two if the weather is cold, to let the oil properly circulate before putting the engine under load. Air-cooled VW guys routinely extend the life of their car's engine by 15 to 25 percent by adhering to this simple practice.

Don't take my word for it. Have your oil analysed. It's emprical. It's easy. It's even fun!  ;D

Humbly submitted,

Spalding

Captain Spalding

Quote from: styria on 02 April 2006, 04:25 AM
Hi Captain Spalding, what an excellent contribution and good to know that you are still in the land of the living. Would be great to hearfrom you more often and it would be better again if you gave us details of your 6.9 and some of your experiences, likes and dislikes. Best regards, Styria
Thanks, Styria, for the welcoming words. I have only had my 6.9 for about 9 months. It has been in my family for years, though. It was my father's, and owing to health issues he found that he needed a car that is easier to drive and to get in and out of. Because of some poor vehicular judgements earlier in my life, my father is reticent to let me touch any of his cars. I have been accident and ticket free for more than 15 years. That man has a memory like an elephant! :P As a result, though the car has been in the family for well over a decade, it is very new to me. So, mostly I have been lurking, as the information I have to offer tends to be of a more general nature and not specific to 6.9s or the 116.

My father put European bumpers on the car the moment he got it. He did this before the advent of the internet, and considers himself to be the inventor of the idea. As I received the car gratis, I am happy to humor him on this. He found the original metallic brown color to be uninspiring, and had the car painted a very lively maroon - a Rolls Royce color. It needs a repaint, and I am inclined to keep it the color he chose. The car also has steel wheels and hubcaps, rather than alloy bundt wheels. I haven't decided what to do there. The derth of properly sized/rated tires has me wondering about moving to 15 inch wheels, but on that car, perhaps more than many others, wheels seem so much to dictate its personality. I've heard tell that there are 15" bundt wheels floating around out there. I've kept my eye peeled on ebay for them, but have so far come up short. I have half-heartedly considered going with a slightly newer vintage Mercedes wheel, but unless I find those 15 inch bundts, I think I'll stick with what I have and pay the premium for the Michelin XWXs.

There have been several projects in line before it, but it's almost time for the 6.9 to receive my full attention. There are some cosmetic and deferred maintenance issues to be dealt with above and beyond the paint, and I intend to deal with them and return the vehicle to its former glory. A bit of mechanical work, new seat covers, and a few pieces of chrome should do the trick.

I'm sure I'll have plenty of questions along the way, and thank everyone in advance for the helpful advice I know I'll receive here.

Spalding


michaeld

Hi Captain Spalding,
Just curious, are you a captain because you drive a big 116 "boat"? or for some more official (but not as fun) reason?

I agree with Styria.  Excellent post on oil.  I learned from it.

But I hope you come back and post one more explanation: I am specifically interested in time between changes.  Your 6,000 miles rule agrees with the Mercedes manual, but what would you do in a car that has only 2,000 miles since its last oil change 6 months ago?  Do you change it - and satisfy the 6 month principle - or do you say, "The oil is fine," and keep it until you build up mileage.

It seems to me that the effect of time is a little more nebulous than the effect of mileage.  I readily agree with Denis that as you put miles on an engine, sludge build-up begins to increasingly become an issue.  But what if you drive 30 miles twice a week?  At that rate it would take 2 years to go 6000 miles (as per Captain Spalding).  It would take nearly a year to go 3,000 miles.  In 6 months you would only have driven a little over 1500 miles.

Here is the question I have been asking: do you change your oil based on your mileage, or based on the length of time the oil is in the car?  I personally would NEVER allow my car to pile up high mileage between oil changes; I would be getting fidgety even after 3,000 miles.  But what if I'm in that 30 mile twice a week group?  How many months - NOT miles - should I wait between changes? 

The Warden

Hooray for Captain Spalding, the African Explorer... ;D

Quote from: Captain Spalding on 02 April 2006, 04:05 AMI went the oil-analysis route. It cost me $90 to have 3 analyses done.

$90 for three analyses?

Have you seen these guys? http://www.blackstone-labs.com/ They only charge $20 per analysis...and, while I haven't used them personally (I keep meaning to do an oil analysis at some point), I've heard many good things about them from other people in the Ford diesel world...

No affiliation; just thought I'd give an FYI :)

Captain Spalding

Quote from: michaeld on 02 April 2006, 11:38 PM
Hi Captain Spalding,
Just curious, are you a captain because you drive a big 116 "boat"? or for some more official (but not as fun) reason?
The Warden has it right. An homage to Groucho Marx. I adopted the moniker when I started Geocaching, then it bled onto several off-road enthusiast sites I frequent. It seems to have become universal as my online persona.

QuoteIt seems to me that the effect of time is a little more nebulous than the effect of mileage.  I readily agree with Denis that as you put miles on an engine, sludge build-up begins to increasingly become an issue.  But what if you drive 30 miles twice a week?  At that rate it would take 2 years to go 6000 miles (as per Captain Spalding).  It would take nearly a year to go 3,000 miles.  In 6 months you would only have driven a little over 1500 miles . . . what if I'm in that 30 mile twice a week group?  How many months - NOT miles - should I wait between changes? 
I agree that the effects of time are not very well documented, and my approach is somewhat seat-of-the pants. I've read a lot of chatter that oils, especially synthetics, can become more acidic over time, and, combined with moisture absorbed by the oil, more corrosive. Hence the 6 month rule. On the other hand, some synthetic oil manufacturers recommend an oil change interval of 25,000 miles. Since most people don't drive that far in a year, they must clearly be comfortable with the idea of the low-mileage oil being effective  at least that long. There are other factors besides humidity. If you have an engine that is difficult to keep in tune, it might produce an unusual amount of combustion by-products which would tend to age the oil more rapidly. Oily or burned spark plugs might be an indication that the oil has been subjected to more than the usual stress. Where does that leave you and I, the automotive obsessives? For vehicles driven less than 6000 miles a year, I feel comfortable with a once-a-year oil change. I think six months is a little excessive. If I lived somewhere tropical, where the humidity is up above 90 percent year round, I might consider changing it more often.

It would be interesting to have the oil tested based on a time interval rather than a mileage interval and see the results.

Cheers,

Spalding

Captain Spalding

Quote from: The Warden on 03 April 2006, 12:28 AM$90 for three analyses?

Have you seen these guys? http://www.blackstone-labs.com/ They only charge $20 per analysis...

They are the lab I use. As well as the standard test, I have the TBN test performed as well, at $10 per sample.

Here are a few interesting reads, just to muddy the water even more:
Motor Oil Myths and Facts
More Than You Ever Wanted to Know About Motor Oil
Oil Change Intervals

Spalding




The Warden

Oh, okay...that makes sense now :)

BTW, my uncle is also into geocaching...and he lives in the L.A. area as well...

alabbasi

I change the oil every 3000 miles on the 79 6.9 and the 73 280SEL 4.5 with Castrol GTX 20w50. On the E420 I use Mobile 1 and change it every 10,000 miles with no problems,
With best regards

Al
Dallas, TX USA.