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the truth about oil change milage.
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03-10-2009, 04:52 PM | #1 |
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the truth about oil change milage.
i always read that people think the oil change is based on certain amount of miles, but this might prove different. got a flyer in the mail today with some cool tips and this is always a topic on here.
"not based on time interval but on how you drive"
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03-10-2009, 05:11 PM | #2 |
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ok so the computer calculates it based on a certain set of threshold parameters. Who says those parameters are adequate technically or were they backed into by financial analysis? Ie calculate the longest possible interval, given an everage bmw driver, that we can run the oil for, given that it costs BMW X dollars per oil change and the cost of not changing the oil is Y dollars of waranty work/vehicle repair (ie the concequences of not chaning oil to often).
Since the consequences of not changing your oil often enough occur into the future, typically to the latter end of a car's useful life, when present valued, that amount would be small when compared to the incremental costs in the short term that BMW has to pay to change your oil more frequently, assuming a certain % of problems or engine failures. In the end, it probably works fine for most average drivers |
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03-10-2009, 05:13 PM | #3 |
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That surprises me, because mine didnt say anything until 1k miles before the 15k service was required...Seems on par with the documented schedule, at least.... However, this concept is a cool idea if it did, infact, actually work that way.
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03-10-2009, 05:16 PM | #4 | |
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03-10-2009, 05:18 PM | #5 | |
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03-10-2009, 05:58 PM | #6 |
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LOL - never mind - thats how an engineer who is now in finance thinks
basically, what is cheaper in the long run for BMW? A) Cost of changing oil frequently but fewer warranty repairs in the future due to poor oil changes B) Cost of less frequent oil changes but more warranty repairs in the future Obviously there are other factors involved, this is a simplification. But in general terms, since the warantee repairs occur in the future, when BMW calculates what this cost would be today, it may be that its lower than the cost of doing a series of oil changes in the short term. Also, not all engines will fail due to poor oil (or can be proven to fail due to it), so assign a lower probability to that number and the present value shrinks even more. I would love to believe that a room full of bmw engineers cranked out the threshold numbers that the ECU uses. Engineers, by nature, over design many things. Once the finance folks get a hold of it, it becomes, lets say more economical or never "flies" |
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03-10-2009, 09:12 PM | #7 |
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There are several things that the DME looks at to calculate the oil life. Miles driven, how hard those miles are driven, how much fuel is used, freeway vs in town, cold engine vs hot, and also the condition of the oil (using a condition sensor built into the level sensor), and probably other stuff that I'm forgetting right now.
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03-11-2009, 02:47 PM | #8 |
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so.... changing according to their interval safe or no!?!
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03-12-2009, 03:32 AM | #10 | |
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That said, I'm not a 'BMW engineer' and my car is leased, so whatever. I'm sticking with the OEM recommended service intervals and calling it a day |
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03-13-2009, 03:36 AM | #11 |
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Yes, Nick is pretty close to the mark. I have access to an oil analysis laboratory through work and get mine checked regularly.
Basically, engine oil wears out which is based on environmental conditions, fuel burnt and mode of driving - obviously the oil quality itself has a bearing on the matter as well. I change mine every 5,000K's which is based on our humidity and the way I drive. If you have doubt, take your oil to a lab and get an IR analysis done on it to see what components are failing in your oil for the amount of K's you do. Fritzables. |
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03-13-2009, 10:18 AM | #12 |
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Not if you plan to keep the car after the warranty expires. All BMW cares about is getting these cars past warranty at the lowest possible cost. The "free maintenance" is essentially a marketing gimmick.
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03-13-2009, 04:47 PM | #14 | |
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03-13-2009, 06:20 PM | #15 | |
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03-13-2009, 06:28 PM | #16 |
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interesting
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03-13-2009, 07:15 PM | #17 | |
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03-13-2009, 11:29 PM | #18 | |
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03-14-2009, 06:29 AM | #19 | |
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So to say that the system monitors the condition of the oil is not the same as saying that the system can determine if the actual oil still meets all of its specs. |
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03-14-2009, 10:55 AM | #20 | |
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From (a lot more on BMW's service interval on this page): http://www.bobistheoilguy.com/forums...095774&fpart=1 * The condition of the engine oil is monitored by a sensor in the oil pan. This sensor obtains the requisite information by measuring the electrical properties of the oil, which change as wear progresses and the additives in the oil become depleted. From a GM forum: * Oil condition sensors in some BMW and Mercedes products are useful, also. They have their limitations, though, as they can be blind to some contaminates and can, themselves, be contaminated by certain markers or constituents of certain engine oils. Oil condition sensors can only react to the specific oil at that moment and they add complexity, cost and another potential item to fail. One other beauty of the GM oil life monitor is that it is all software and does not add any mechanical complexity, mass, wiring or potential failure mechanism. |
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03-14-2009, 04:35 PM | #21 |
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So this is the 20 millionth thread on this subject. I think I am the only one I've read that has actually followed the oil service schedule on my BMWs. I have a 1989 E30 with 293K miles; 12,000 mile oil change intervals. 120,000 miles was on non-synthetic oil (but with BG additive early on). I switched to Mobil 1 at about 130K miles. The motor is still running fine. I also have a 1997 Z3. Oil changes average also about 12,000 mile intervals. The car has 140K miles. The engine runs perfect. My E90 has 75K miles, motor is strong as the day I bought it. I've averaged about 17,500 miles between changes. I am the original owner of all three cars.
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03-14-2009, 05:54 PM | #22 | |
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I change my oil at every 20kmls. BMW system might tell you 40k will do, to me degrading oil will cause accelerated wear which typically starts to show itself way after the warranty period. I (now) run my cars for 4-5 years, 120-150 kmls total, and to me the additional oil changes is peanuts compared the knowledge of having good oil This thread is only on what the ECU calculates, and at least I learned a thing or two. But I'll still change my oil at 20k as there's loads of other factors, and certainly with EGR on diesels. |
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