Road & Track on oil changes

In the new R & T the question is raised by a reader of whether you should change your oil more frequently than the recommended 15K with the synthetic oil used in BMWs. The response was that essentially you are wasting your money as synthetics do not break down like regular oil and the filters are also designed to last for 15K. They go on to say that engine failure is rarely the cause of why people get rid of their cars or the source of major expense with a car. They also note that the primary cause of premature engine failure is driving the car hard when it is cold and not allowing the oil to fully circulate before running at high RPMs.

I think in some respects BMW is putting its money where its mouth is in this regard as they are offering the maintenance and warranty to 100K. Other companies are also offering warranties to 100K and my Honda Pilot extended warranty to 6 YRS 100K cost me $1100 so they are not figuring that I will need an engine rebuild before that time.

My thought is that perhaps since we love our cars so much we are going a bit too far in some instances and we have to recognize that part of a well made car is that it is going to last. I think that people will eventually realize that BMW is a great car and you can pay the same price as a Mercedes and not have any service or maintenance costs.

Maybe it is a waste of money to do more periodic oil/filter changes.

But it's really not a LOT of money, and as long as there is debate on the subject, I figure more periodic oil/filter changes can't hurt. I'd rather err on the side of caution.



And besides, I wouldn't trust R&T to advise me on this.

Originally Posted by jerrykdc

I think in some respects BMW is putting its money where its mouth is in this regard as they are offering the maintenance and warranty to 100K. Other companies are also offering warranties to 100K and my Honda Pilot extended warranty to 6 YRS 100K cost me $1100 so they are not figuring that I will need an engine rebuild before that time.

Warranties are just like insurance. Let me give an example. Lets say 10% (1 of ten) of the cars, following manufactuer's recommendations, will need a new $5000 engine after 100k, and they charge $1000 per car for the warranty. On average, they collect $10k (ten cars worth) for every $5k engine. Hence, they make $5k, and the deal makes sense to them.

However, would you do something to your car if it had a 10% chance of not making it to 100k? I view oil changes (I plan to do my BMW at 7500 mile intervals or six month which ever comes first) as cheap insurance as oil degradation. Just because the oil passes spec at 15k miles doesn't mean its as good as it could be.

I'll agree that major engine failure is rarely the reason we get rid of a car. Heck, generally when we send a car to the junk pile in the sky it is because of an accident or because swapping out the alternator costs more than the car is worth.

That's why these people that change their oil very frequently are kidding themselves when they think it will mean a more reliable car. While the engine may benefit some, the internals are incredibly durable. Oil changes don't help prevent the 99.9% of problems we see, and that happen to be unrelated to engine internals.

Originally Posted by Plaz

Maybe it is a waste of money to do more periodic oil/filter changes.

But it's really not a LOT of money, and as long as there is debate on the subject, I figure more periodic oil/filter changes can't hurt. I'd rather err on the side of caution.



And besides, I wouldn't trust R&T to advise me on this.

If R&T is correct that engine failure is not a result of engine oil breakdown rather it is primarily caused by poor cold engine driving habits, then the 10% or 5% engine failure which could occur prematurely can be avoided by following their recommendation by driving conservatively until the engine is at operating temperature, so there is no need for the extended warranty, at least so far as engine failure is concerned. There are many other parts of the car which can go bad prematurely and make the warranty worthwhile, but engine failure may not be a justification for spending the money. The extended warranty for my car is around $2000, and if we put the engine aside, what is the likelihood of incurring $2000 in expenses for other items needing repair? I don't know the answer to the question but I don't believe it is obvious.

Originally Posted by Plaz

Maybe it is a waste of money to do more periodic oil/filter changes.

But it's really not a LOT of money, and as long as there is debate on the subject, I figure more periodic oil/filter changes can't hurt. I'd rather err on the side of caution.



And besides, I wouldn't trust R&T to advise me on this.

I agree that it is more for piece of mind than anything else. I know conventional oil lasts far longer than the 3,000 miles suggested. I have asked around and found the same to be true with the BMW synth oil. Those I asked said it was good until 15K, but if I felt better to change it earlier. Does it hurt? Nope. Is it necessary. I don't think so.

If it makes one feel better/safer/etc/etc/etc to chanage the oil AND FILTER more frequently than the manufacturer recommends, then that is what you should do, just don't got to absurd extremes.

I think that the oil is probably good for something close to the 15K under "normal" driving conditions, but what is "normal" and how often are we driving that way? I worry more about the filter breaking down and letting all that grit circulate through the engine. The first round of BMW long life filters were known to not last a full 15K... who would've paid for the reduction in engine life because of that??????? Certainly not BMW

Of course, you shouldn't listen to anyone about how (in)frequently to do it, but take samples of your oil every now and then and have them analyzed and then go by that to figure out the frequency of oil changes.

I would guess that the cooling system (pump/fan/radiator/fluid) is the cause of more engine failures than how often you change the oil.

Not to mention a engine failure is the least of your worries when owning a car.

Originally Posted by operknockity

take samples of your oil every now and then and have them analyzed

Honestly, I think only the most devout geeky gearheads do the Blackstone thing for their personal daily driver. Before reading this board, I'd never heard of anyone sending their used motor oil to be analyzed. I mean really, that's pretty over-the-top. (Not that there's anything wrong with that)

full synthetic mobil 1 oil change (5w-30) 30$ at WALMART

worth every penny for me to have done every 5000 miles.. probably the reason i got 270,000 miles out of my 535is before i sold it.. i still see it around.. has well over 300,000 on it now.

Sure synth oil won't break down as rapidly - but contaminents and such build up just the same and these can cause extra friction as well as gunky buildup and such. And 15K under ideal circumstances...if you drive hard and in dusty areas etc etc and if your engine has hot spots that can break even synthetic oil down prematurely...you just never know. I'm just not comfortable going 15K+ without changing out the oil - regardless. Its a peace of mind thing. Have 6700 miles on the Bimmer and already changed the oil/filter once. I change the oil in the Audi approx every 4-6K miles.

Originally Posted by Plaz

Honestly, I think only the most devout geeky gearheads do the Blackstone thing for their personal daily driver. Before reading this board, I'd never heard of anyone sending their used motor oil to be analyzed. I mean really, that's pretty over-the-top. (Not that there's anything wrong with that)

I honestly don't fall into that category (I don't think ) yet send my oil to Blackstone at every oil change. (Used to get a TBN number every time, now I don't need it)

I had heard about these labs, before reading it on this board, from friends that are pilots/airplane owners. See, you can't just pull over and stop the engine in an airplane. Besides pulling plugs and checking their condition, oil is analyzed as well.

As for changing oil before the recommended 15k interval, unless you have it analyzed and know it's condition, then you are simply shooting in the dark and have no clue if the oil is still of use or not.

That said, with my car with my driving habits, oil can go up to a max of about 8k miles before it's basically useless.

Originally Posted by SergioK

I honestly don't fall into that category (I don't think ) yet send my oil to Blackstone at every oil change. (Used to get a TBN number every time, now I don't need it)

I had heard about these labs, before reading it on this board, from friends that are pilots/airplane owners. See, you can't just pull over and stop the engine in an airplane. Besides pulling plugs and checking their condition, oil is analyzed as well.

As for changing oil before the recommended 15k interval, unless you have it analyzed and know it's condition, then you are simply shooting in the dark and have no clue if the oil is still of use or not.

That said, with my car with my driving habits, oil can go up to a max of about 8k miles before it's basically useless.

Well, you're definitely a gearhead... I'll leave the geeky characterization to others to determine. (Raffi?)

It's also different because you track your car regularly... there's more justification to see what punishment you're doling out on your powerplant and your oil.

You're right, it's shooting in the dark. I have no clue... but 7500 seems as good an educated guess as any.

Attached is the discussed segment of the February edition of Road&Track:

This is a great question we cannot answer definitively on a mechanical basis. It’s not from a lack of research, but rather the limited data available and the large number of variables involved simply won’t allow putting this question to rest.

If you’ll let us put forth our hunch, however, our guess is the extra oil change will not yield extended engine life. Assuming a proper oil level, operating conditions play a greater role in engine longevity compared with what we’ll assume is a minor amount of dirt or a somewhat depleted additive package in the oil.

Let’s consider your well-driven, well-cared-for BMW. Because synthetic oil is so stable at high temperatures, it does not so easily cook into uselessness like mineral oil, which is where the extended oil change intervals mainly come from. Assuming a serviceable, un-punctured, not over-loaded air filter, tight engine sealing and paved roads — some of us still motor over dirt driveways or roads — then the oil filter ought to trap what harmful particles come its way for 15,000 miles. Given that, typical use should not allow much wear of the bearings or cylinder wall environment (piston and rings) or the valves and their guides.

Allow dirt into the system via cracked seals or an overloaded air filter, and engine wear will accelerate because of dirty oil. Then, of course, frequent oil changes help.

But the real disaster is no oil, and not just from low oil level on the dipstick. Winging the engine to redline and holding it there, especially on a cold engine, might pump most of the oil into the valve cover before it can drain back enough to keep up with the oil pump’s demands. Then you have real engine wear. Hard, sustained cornering can force oil away from the oil pump pickup in the pan, accomplishing the same thing.

Furthermore, consider that most engines go out of service for reasons unrelated to oiling. Very often the rest of the car wears out first; cracked dashboard padding, leaking weatherstripping, faded paint, crash damage or even plain old boredom on the owner’s part has sent more modern engines down the road than wiped-out bearings or scuffed pistons. And if the engine does fail, often it is the highly stressed valvetrain that gives up first.

Our guess is that sticking to BMW’s official oil change recommendation and scrupulously maintaining all other aspects of the engine will return maximum engine life. As for your Honda experience, those engines use very fine screens on their oil pump pickups, along with mineral oil. Gunked-up oil doesn’t flow well through those tightly meshed screens, so extra diligence in the oil change department pays off with those engines.

Oil is the engines garbage can, by products of anything that goes on, from combustion to particles of what have you from friction and wear end up here. The Synthetic may very well out last the regular – from a molecular point of view - but, the cleanliness of the oil (or lack there of) is what is going to kill your engine.

If the cars were outfitted with both an oil temperature gauge (so I can tell if the oil is being over heated), and a differential pressure gauge on the oil filter (so I can tell how clogged the filter is), I would be more able to accept the “super long” service intervals if I was able to check on these items myself.

In the early days, car engines were maintained on an “hours run” clock. People prefer to read odometers, enough said.

Lets consider that some bearings (be they roller or bronze) in heavy equipment are only designed for 3500 hours, if one does some math for a typical car based on 3500 hours life with respect to km driven (ignoring all the stuff a real engineer would consider):

3500 hours at 60 kph = 210000 km driven

Say we are driving on the highway (with a little speeding… lets be honest):

3500 hours at 120 kph = 420000 km driven

24000 km between oil services, average speed being driven is 60 kph = 400 hours.
Roughly 8-9 oil changes before the service life of the bearing has expired (statistically).
8000 km between oil services, average speed being driven is 60 kph = 133 hours.
Roughly 26 oil changes before the service life of the bearing has expired (statistically).

I would hazard to guess that most people don’t drive their cars till 210000 km, and when I think about it, 3500 hours sitting in a car, my commute is 1.5 hours total each day, for 2333 days, or 6.4 years. I don’t know if I will be around in 6.4 years!

I also think that the oil change intervals probably make little difference in the overall lifespan of the car. There are so many other things that can and do go wrong before the engine starts to be a problem. That being said, I think we latch on to it as a way to feel like we have some control over the reliability of the car. Other components that are a nuisance and sometimes costly to replace will fail many times before the engine will (window regs, subframe tears, various sensors, cooling system, etc)

Why do people do frequent oil changes?... it makes them feel better. Almost noone here can say for a fact that double or tripling the recommend oil change will extend the life of a BMW inline 6.