Is Putting Synthetic Motor Oil Worth It? - BMW Forum - BimmerWerkz.com
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#1 (permalink) Old 11-08-2004, 02:09 AM
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Just got a 1990 525i. Has about 130k miles on it

First oil change coming up, is it worth it to go with synthetic or just get regular stuff?
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#2 (permalink) Old 11-08-2004, 03:57 AM
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I think my car had regular oil in it when i bought it. But I changed to synthetic. No problems so far. Secondly, synthetic works better in winter, so i heard.

Sry didnt really answer your Q.

Couple Qs for Techies:
1) How frequently should u change synthetic oil?
2) Can you switch back and forth between syn and reg?

For 1)----> Opinion A: You can go for 6K miles with synthetic..no probs
Opinion B: I would rather change it every 3K miles or 3 months no matter what kind

For 2)----> Opinion A: Yes, you can as long as you flush your engine.
Opinion B: No, once you go synthetic, you stay synthetic.


Another random opnion: For high mileage cars, you should use high mileage oil. It has additives which stops leaks coz of wear and tear.

What if I had oil pan gasket, axle seals changed recently? Do i still need high mileage oil?
---------It works on ur piston rings too. (really?)

All your opnions and answers are welcome and respected. Thanks for your time reading this.

Best,
TheHire

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#3 (permalink) Old 11-10-2004, 06:51 PM
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I've written many times regarding synthetic oil. I have discussed the topic at length with other mechanical engineers & lubrication engineers (at SAE meetings) and seen test data/charts and here is the deal:

1) Up to the SF/SJ (or is it SH?) standard, there is very little difference between the synthetic and conventional. One of the tests considers the oil's ability to lubricate over time in specified conditions.
2) As soon as the standard is exceeded (time/mileage/temperature), the oils diverge almost immediately, with conventional oil going "South" rather quickly, whereas synthetic shows a much more linear degradation. Oil additives (brand-specific) have a lot to do with oil's long-term stability too.
3) Synthetic blends behave only slightly better than conventional, and exhibit the same accelerated degradation of conventional as soon as the standard is exceeded. So you don't get much benefit with them.
4) Mobil engineers presented a project where they obtained a brand new 3-series BMW, filled it with Mobil-1 and then drove it 1,000,000 (one million) miles and then took the engine apart and mic'd all bearings and ciritcal dimensions - all were still within NEW specs (not just service limit) (!)
5) When Mobil-1 was first introduced it was claimed to be good for 25K miles between changes. This brought a lot of heat to Mobil from auto manufacturers and consumers over warranty claims (customers didn't follow specified change interval, which was written for conventional, but then when there was a warranty claim having nothing to do with oil, manf tried to get out of warranty coverage).
6) Its best to start with synthetic when the car is new and stick with it - cars that are "used to" conventional may burn more oil when switched to synthetic. In that case try going up a weight (from 5W-X to 10W-X)

Conclusions?
1) If drive in basically "normal" conditions & you insist on changing oil every 3K to 5K miles (and you NEVER exceed 3K), then you are just as well off using conventional oil because you are not really stressing the oil
2) if you drive in harsh conditions, or need to go longer between oil changes, then synthetic's more linear properties AT THE SPEC LIMITS AND BEYOND give you added insurance. My policy is to use synthetic & aim for 7K between changes, but feel it's OK to go 10K on occasion if you must (and 25K is probably still fine, but I'm not going to try it). I drove my 1994 Legend 189,000 miles following this policy and it burned not a drop of oil between changes, even on the day I sold it.

Note that some engines may be designed with local hot spots or with certain high-temp features (e.g. turbochargers) that make synthetic mandatory regardless. On my BMW, I plan to run either Mobil-1 0W-40 or Syntec 5W-50 and go about 7K between changes as described above.

So that's MY 2 cents. Sorry so windy, but this is such a misunderstood topic.

Oh, and if you switch back-and-forth, that's OK, just remember that there's still a little bit of the "old" oil left in there at every change.

<span style='colorurple'>Eric S.</span>
2006 Honda Odyssey EXL-RES
2006 Honda Accord V6 EX-L Sedan
1999 BMW 540i 6-Speed (Sold to M3UOND on 9/21/06)
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#4 (permalink) Old 11-10-2004, 06:53 PM
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Oh, and yes, synthetic does have much better cold-flow characteristics. So if you live in, say, upstate NY and store your car outdoors, then I'd HIGHLY recommend using a 0W or 5W synthetic.

<span style='colorurple'>Eric S.</span>
2006 Honda Odyssey EXL-RES
2006 Honda Accord V6 EX-L Sedan
1999 BMW 540i 6-Speed (Sold to M3UOND on 9/21/06)
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#5 (permalink) Old 11-10-2004, 08:10 PM
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If we assume start up and heat are the most important factors to look after in oil changes; one would think additives and foaming can be less relevant as major factors if we change our oil on a regular basis. That is refreshing our engines with fresh oil when the old oil has been degraded in its very chemical properties alas ERIC S.
Having said that (got myself in trouble I suspect) Let me pose and ask you the following to lubricate my thought in sythetics:

1. Is it true that many chemical properties of synthetic oils such as Pour Point, Flash Point, Evaporation are similar in all synthetic oils?
2. Is it true BMW synthetic was made by Valvoline or Mobile (they have their own Mobile 1) for the 40W grade; and now Castrol make the BMW 30W after the Mclearn F1? If so why not mention it on the Qrt. by a patent name?
3. Is this why the High Performance BMW synthetic oil is still PATENT PENDING? Look at the buttom of the gray qrt.

For start ups?
Can I argue (safely though) that my crank bearings and rocker shafts and cam lobes and rocker scuffs get more wear during my 8 dry starts (oil change every 3.000miles=1 dry start) than an engine in Iraq getting an oil change in 24.000 (1 dry start) miles interval? Think trade offs here!!

Switching back and forth? umm
If we talking transmission then I'll take the fifth on this one because synthetic fluids can make a big difference and hense the life-time stuff was covered in details in another post.

regards
billb
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#6 (permalink) Old 11-10-2004, 09:23 PM
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some people have experienced problems (leaks) when switching from regular to synth. at such high miles.

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#7 (permalink) Old 11-11-2004, 01:54 AM
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Yeah, the Mobil guys did admit that synthetic, thanks to its slipperiness (technical term ) would leak past some gaskets where conventional didn't.

TO answer Bill B's musings - The data I saw was presented by Mobil engineers, who we must acknowledge up front are likely biased. But since this was a technical society presentation, from engineers to engineers, I would hope the bias wouldn't skew things too much. That said, they emphasized that since additives are pretty much proprietary and govern oil's long-term stability, they claimed Mobil-1 as superior to most other synthetics. However the data they showed looked to me like there wasn't a lot of difference between synthetics, at least nothing near the difference between synthetic and conventional. Regarding the individual characteristics, I think they addressed that, but I don't recall the outcome (I was and am using Mobil-1 anyway, so once I had the smug assurance I was using a good product I didn't pay attention to such detail, sorry).

Regarding BMW-specific oil, I plead the 5th, as didn't previously know there was such a thing, so I am Sgt. Schultz on that topic.

The start-up issue is a big one. Yes, that crank is just sitting flat on that bearing when it isn't turning, but once it gets spinning it starts riding on that film of oil, not touching the bearing at all (or so goes the sutomotive engineering chapter on the subject). So while start-up wear is undeniable, I must point out that every time I've looked at engine bearings on used engines (I'm not a pro mechanic so the number of times I've done this is about 5 to 10 times), I've always seen oil coating 100% of the surface. So my instinct tells me you get "some" benefit at start-up from this entrapped oil, the Q is how much.

I guess I should have pleaded the 5th before I started typing this. Sorry so wordy...

<span style='colorurple'>Eric S.</span>
2006 Honda Odyssey EXL-RES
2006 Honda Accord V6 EX-L Sedan
1999 BMW 540i 6-Speed (Sold to M3UOND on 9/21/06)
1991 Honda Civic Si - Occasional Beater
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#8 (permalink) Old 11-13-2004, 04:31 AM
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all great answers, thanks a lot guys
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