I have a 91 420SEL with approximately 98,000 Miles on it. I have tried three different independent mechanics and have received 3 different answers regarding the how often to perform a oil/filter change. One say every 5000 Mi and refers to the maintenence schedule in the owner's manual. One say every 3000 miles. The third say every 3750 miles. What is the recommended milage between oil changes?

If you plan on having the car forever, change it every 3,000-3,500 miles or every 3-4 months. Everyone is a little different, and many change theirs at 5,000 miles. I, along with most everyon on this forum, agree that 3,000 miles is a good distance to go between oil changes.

But if you do a search, you will find a ton of info. Oil is a hot topic around here!! Good luck.

Change Oil
 

Bill! I would keep the oil clean and change it every 3000 miles. Good Luck Gary

There's one thing about oil change frequency that will get little argument(although there are those who will argue with me on this), and that is you just won't hurt anything changing it TOO often.

Oil and filters are CHEAP! Engines are NOT! Especially MB engines.

Change oil hot and change oil often,

Changing it too often is horrible. It causes all kinds of stuff to seize. The oil never gets "broken in".

My mechanic said that as hot as a topic as this is, the only cars he has ever seen have oil related trouble are from those people who DON'T change oil and those who change it like every 1,000-2,000 miles. I trust him, he's a 6 time MB Master Guild technician and currently the Shop Foreman at the biggest dealership in the southeast.

Change conventional at no more than 5,000.

Synthetic between 7,500-10,000.

No offense Larry, just disagree with you strongly here (yet VERY respectfully :) ).

Are you really serious?

Now that's something I've never heard of... makes me curious.... very curious!

BTW, check out this short post!

http://www.peachparts.com/shopforum/featured-cars/18607-i-saw-1990-420-sel-462k-miles.html

[Edited by David C Klasse on 05-30-2001 at 04:37 PM]

David, where do find these guys?

Let's see 3000/14 = 215mi per day or so. Living in and around L.A. that's not out of the question...

But the point you made earlier is one most don't focus on and that's time! If your car is sitting around in a garage it's still collecting moisture inside the engine. I like the 3-4month rule and live by it myself!

Ed,
Of course that's not out of the question, but I'm sure that only a VERY small percentage of the population (even in LA) drive over 200 miles per day. That is a LONG commute. Sure it's possible, but not likely.
I average 2,000 + miles per month, probably more, but I try and not put on more than 500 miles per week, and I drive a lot.

So Ed, sure it's possible to drive over 200 miles per day, but I don't really think many peopl do.

New oil is better than old oil.

Synthetics are better than conventional.

Changing more often is better than not often enough.

Don't get weird.

George Stephenson

I knew a guy who lived in Palmdale and commuted to Santa Monica every day. He said it actually took him less time than if he lived in Glendale or Pasadena or Burbank. He drove a little econobox Suzuki Swift and I never once heard him mention that it was in the shop.

Anyway back to oil, I find it hard to believe that oil breaks in. Breaks down maybe, but in? I'm willing to give this one a good listen. I always though breaking in was a process where contact surfaces smooth out and form a sort of symbiotic relationship with each other :)

Kuan

That "break-in" I referred to applies to conventionals only. Sorry for the confusion.

Breaking in oil?????? Oh come on. Never seen an engine wear out because of clean oil. I think there was something lost in the translation somewhere.

David,

I wasn't only talking about the every two week guy, what about the break in the oil guy?

Gimme a break! Pun intended ;)

I say change it as often as you see fit.

If you want to change it every 2 weeks, go for it, its your dime. If you want to change it every 3-4 months, go for it!, if you want to change it at 2k, 3k, 4k miles, do, just remember to do it on a regular schedule, and do what makes you feel comfortable.

If you feel comfortable changing it every 3k then do it, if you feel comfortable doing it at 4k then fine, if you feel comfortable doing it at 1k then thats fine too, or at 2 weeks, its all good.

Just don't forget to change it.

I myself have also never heard of oil needing to break in. If thats the case, then why would you want to put in new oil, wouldn't the oil then come pre broken in from the manufacturer?

Alon

What is clear to me in this discussion of motor oil is that it can quickly fly off in the direction of the mythological. I really believe that deep down we are all looking for that magic bullet, the snake oil that will be the eighth wonder of the world, a miracle. Not unlike the quest for meaning in this life. Did I just go off the deep end? :D
Thom

Ed,

I lost you.... that must have gone over my head.

I guess most people realize that I am opinionated. But, I think that my saying that the breaking in of oil is as ridiculous as anything I've ever heard, is not opinion. No, I take that back. The breaking in of oil IS DEFINITELY the most ridiculous thing I've ever heard.

Let's get real here!

I'm not here to cause any friction over the use of oil. Perhaps there IS a certain benefit to be gained from slight breakdown in oil. I really, really, am, open to this suggestion. However, I'm not so sure that even if the oil does break in, that the limited time where the oil exhibits enhanced lubricating properties, will justify leaving it in the engine for a longer period of time.

Kuan

I agree with Larry
 

I have never heard of "breaking" in of oil and have always been most successful by changing it every 3k miles. The last engine I tore into I had changed the oil every 3k miles and the inside was spotless with the original cross hatching showing in the cylinders and it had 125k miles on it.
Jim

Keeping Metal From Contacting Metal
 

I've never heard of oil needing to be broken in. This is why you change oil in the first place, to keep it fresh, clean and new. Oil is designed to keep friction and metal to metal contact at a minimum. After you change the oil in your Benz and start the engine, the oil starts to break down.....slowly but it eventually does break down.

I change the oil in my 240D every 1500 miles with Mobil Delvac 1300....Maybe changed too often but I believe in removing all the soot and impurities from inside the engine as much as possible to have the engine operate in the cleanest oil possible. I change it hot and often per Larry's motto.

If oil needed to be broken in, we would never change our oil.

Herb
'82 240D
114,000 miles

Jim,

What is that cross hatching thing?
I would assume that it's some very thin lines or whatever inside the cylinders but what are they for?

/Daniel

Cross-hatch is the name of the pattern created when you run a honing device on the inside of cylinder walls. This device consists of three pieces stone mounted in a spiderlike fashion so they exert pressure against the inside cylinder wall.

Once again, back to oil, and of course coming from me this is unrelated. Chinese restaurants often save some old oil to mix in with fresh oil when stir frying your food. This is a part of the wok flavor we so desire when we have a hankering for shrimp fried rice.

Kuan

Well, I guess I will dive in. I changed my oil last time at 5K and it still looked quite clean. I am going to 6K on the next one. Admittedly, my type of service is very easy on oil. I commute 150 miles a day round trip and it is almost all highway. Lately, I have been mixing four quarts of regular oil (10W40, whatever is on special) and one quart of Walmart house brand synthetic, which they seem to have stopped carrying for some reason. Probably so I will have to buy the higher priced, heavily advertised name brands. I think most people can go at least 4K and 5K would probably be fine. Changing very often doesn't hurt anything, it just uses up more oil and money. Oil "breaking in" should go into the oil mythology hall of fame along with "can't mix synthetic and conventional" and "can't mix brands". The major impediment in pushing drain intervals for me is psychological: I start to get real antsy to change after about 4500 miles. Lubricants are very high quality these days. Also, cleaner fuels such as low sulphur diesel and unleaded gas help greatly to extend intervals by reducing oil contamination.

The concept of "breaking in oil" is clearly preposterous. The only thing that happens to new motor oil when run in your engine is that it begins to break DOWN. This is simple chemistry. Let's embrace reality here. Change it HOT and OFTEN!

Wok oil vs. MB engine oil? APPLES and ORANGES!

IMHO

Primo

I would like to add something else here to what Primo said. Oil begins to break down from the get-go, as he said. But, oil also begins to get dirty from the get-go. Actually, probably the most important reason for changing oil is that it's the only way to clean the crankcase. By-products of combustion deposit all kinds of nasty things in the crankcase including acids, moisture and other contaminants. Unless you have a little miniature man with a scrub brush that you can put to work in the crankcase, draining the old and pouring in new is the ONLY way you can clean the crankcase of all these nasty contaminants.

Lubricants have advanced drastically, and not only the great synthetics, but the dino oil as well. The base stock in the dino oil is much the same, but the additives, and the particular blends of all these great additives have taken a quantum leap in recent years. These improved blends do indeed allow you to run the oil a little longer than in years past. But, keep in mind that to keep the engine purged of all these corrosive contaminants, you must drain the oil. The more often you drain it, the less nasty contaminants are down there working 24 hours a day, trying to eat everything up.

I'm very glad to see that I'm not the only one here who believes that the idea of breaking in oil is "preposterous".

Have a great day,

some things to consider...
 

most of you already know and will agree that oil changes are probably the most important maintenance procedure there is for a car.

that having been said, i see this issue of "breaking-in" oil a couple of ways. but first, let's look at the function of the oil in order to provide everyone with some background info that not all people may be aware of.

crankcase oil serves several purposes. it lubricates, cleans and cools the engine. it has been said that oil in an engine is the equivalent to blood in the human body. as you all know, blood's pretty important.

on the lubricating end, oil provides a protective layer between the moving parts to prevent/reduce wear. with the extremely tight tolerances produced by today's machining methods, this becomes more critical than in engines of a few decades ago because the amount of space between parts has been reduced from say .012" to in the neightbourhood of .003".

oil also operates as a medium in which particles in the engine can be suspended and kept away from the critical moving surfaces. this is why it is important to change the oil hot. by running the engine to operating temp, not only does it make the oil flow easier, but it allows all the dirt and sediment to be suspended within the oil as opposed to being stuck at the bottom of the oil pan where it doesn't get removed from the engine and just contaminates the new oil.

remember when new cars needed to be "broken in"? this meant initially driving at slower speeds and gradually working your way up over a period of 5,000-10,000 miles. if you'll all recall, the first oil change was usually around 1,000-1,500 miles. that's how it was with my jeep.
because the degree of precision was less then than it is now, the components needed to wear against each other in order to seat properly. this is why oil changes during the break in period was so crucial. the particles that had worn off needed to be removed from the engine.

now that is not as neccessary. as can be witnessed by manufacturers claims that one could drive up to 10,000, or in some cases 20,000 miles before needing to change the oil.

the key factor with oil is its viscosity. that's why there are different grades available for different times of year. summer grade is usually 20-50 and winter grade is 10-30, and we all know that 20-50 is noticably thicker.

thermal breakdown of oil begins immediately. and thermal breakdown is not a good thing. it reduces the oil's ability to lubricate the engine and also reduces the oil's ability to cool the engine because the thinner oil will heat up faster. this is just basic thermodynamics.

the other downfall to waiting too long is the buildup of particles being suspended within the oil. at some point, the ratio of particles to the volume of oil reaches a level where it becomes destructive and could actually result in faster wear of critical components.

on the basis of the function of the oil in relation to the engine, it's better to change the oil more frequently than less. however, you have to balance the need of changing the oil with the cost. it's pointless to change the oil every 1,500 or 2,000 miles because the oil hasn't broken down to the point of being useless and you wind up just wasting your time and money.

by the same token, pushing your oil beyond 5,000 miles is not good either because of the level of breakdown that has occurred.

every 3,000 miles is generally accepted as the best interval at which to change the oil and filter.

now, with regards to breaking in oil. probably the only argument in favor of this is that if you choose a grade that is too thick, you can do damage to your engine as well. thicker oil takes longer to heat up and moves more slowly, so, in a cold start situation, the oil takes longer to circulate through the entire engine on startup leaving some parts unlubricated for a longer period of time. it's also more strain on the oil pump, and other components to deal with the thicker and heavier oil. which is why you should always follow the manufacturer's recommendation for the grade of oil that you use.

as far as synthetics go, they are advantageous because they don't break down as quickly as conventional oils so you could go longer with a synth before it breaksdown completely. BUT, remember what i said about suspending particles and the number of particles per volume of oil? that still applies. although synthetics reduce wear and hence the number of particles over a given period of time than the conventional oils, clean oil is every biut as important as oil that has maintained its viscosity.

i personally don't used synths because i change my oil every 3,000 miles and i am religious about this. and considering that synths cost almost 2x as much as conventionals i'd rather change twice as often and CLEAN the engine twice as often. than spend twice as much and letting the crud sit in my engine twice as long.

a couple of other notes regarding oil:
the molecule of a synth is considerably smaller than that of dino. this is why quite often when switching to synth, people discover oil leaks that didn't exist before.

because synth doesn't break down as fast, this is why they can make synth more of a multigrade than dino and still retain the effectiveness of the oil.

too much oil in the crankcase results in cavitation in the pan by the crankshaft. this puts too much air into the oil in the form of bubbles and results in less oil and more air being pumped through the oil journals to the bearings, etc.

*bell rings*
and that concludes today's lesson :-)

If anyone is interested, I have some "broken in" oil for sale.

Hi Yen-Hsen Liem,

Only comment from me is:

Change your oil at 5,000 and use synthetics. While changing conventional oil at 3,000 is good, it isn't as good as it could be.

I will actually go further ... change your oil at 10,000 and use synthetics ... change the filter every 5,000 ... and, this will still be better than changing convential every 1,000.

In this case, there is no substitute for technology.

George

hehe good one brian. :)

I agree that changing it ona regular basis is key, mileage will vary but regularity is what I look to do with my oil, regardlessof mileage.

If I hit 3k before I hit 3-4 months, I change it, if I hit 2k in 3-4 months (highly unlikely for me) I still change it.

I generally use thicker oil here in southern cali, because temps are usually quite warm. :)

I agree that breaking in oil is one of the strangest things I have heard, and oil has been discussed here so often, we could probably make a seperate forum just for oil. :) hehe

On another note, I agree with Larry about changing it hot and often, because it is the only way to clean the crank case without openeing up the engine.

Since I got my topsider, I will be doing the topside method most often, but will do the "let it drain overnight method" of larry's at least once a year, to get out some extra sludge.

On another note, My boat has never had frequent oil changes, but it still runs great, In fact I change the oil in it probably once a year, and in 17 years have only put 435 hours on the boat. But then again, The boat sits for several months every year, and I always change it before I take it out the first time for the year, and I will sometimes change it after the season if I have used it more often. But I generally only get to take it out 4 times during the summer anyway. I never run the boat with the oil that has been sitting for several months, and I usually change it, Drain it, and change it again before starting it up the first time to make sure I got out the crud. Of course the oil in the boat since I changed it on saturday is perfectly golden in color as it should be, and it is quite thick 15W40 I think, but you need it thick with a high revving 260 hp mercruiser engine. :)

But be rest assured if I used the boat more often, I'd change it more often. The boat does not see the same daily driving that my car does, so the car gets frequent, hot oil changes while the boat gets a yearly change.

Like I said beofre, do what makes you feel comfortable.

I feel comfortable following Larry's Advice and Recommendations for oil, methods of changing it, and frequency of change, so I will go by whatever he tells me to do about my oil. :)

One last thing, and as always, take the old broken in oil to an oil recycling place.

Alon

Some people, like searaypaul, use the broken in oil for their lawn mowers. :D How's that for recycling?

heh, Kuan :)

I don't know Kuan????
I think you may be playing around with hash oil too! ;)

Brian, is that wok oil, lawnmower oil or Mobil 1 cause I'm interested in using "good" oil!

Any shipping and handling fee?

If you needed to put oil in your car and there was no motor oil with a hundred miles, what oil would you use? Canola oil? Olive oil? Peanut oil? Soybean oil?

Worse yet, if you ran out of oil and had to fry up some chicken what would you use, synthetic or dino? I'm gonna let you guys in on a little rumor. This is only a rumor, but it's been circulating in the restaurant industry for a bit. Some establishments which rely heavily on their fryers for cooking sometimes add a little motor oil to the fryer oil in order to "extend" the life of the oil! Just a rumor.

Kuan (rumormonger) :D

What about Vitalis??

that's the consensus
 

Chenage it like the doctor ordered, every 3k miles, but every 5000 for synthetic.