Pagoda SL Group
W113 Pagoda SL Group => Drive train, fuel, suspension, steering & brakes => Topic started by: Theo on March 04, 2011, 16:21:13
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There have been different view on synthetics over the last few years. One is that the modern detergent qualities of Mobil 1 can impair gaskets and seals and that the additional lubricity (?) of a synthetic is unnecessary for a 1963-71 engine. The opposite view is that additional lubricity is always good, always reduces friction, heat and wear, and that that the tendency to leak can be overcome by using higher viscosity ie 20W-50, as long as not in a cold climate area. Which view is correct?
Theo Benz
1966 230SL
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Theo,
we had numerous discussions about synthetic oils.
Here are a few of them for your reading pleasure:
http://www.sl113.org/forums/index.php?topic=10753.0
http://www.sl113.org/forums/index.php?topic=8522.0
http://www.sl113.org/forums/index.php?topic=2800.0
Let us know what you conclude? ;)
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The views on synthetics are all over the board. My gloss: for a newly rebuilt engine with all new seals and gaskets its better to use synthetic. For an apparently original 45 yr old engine like mine its a risk, difficult to quantify. The additional lubrication of a synthetic reduces wear, friction & heat, I haven't seen anyone deny that, subject to the zinc issue, which is not a synthetic/non-synthetic issue--the % of ZDP/zinc additives is (?) independent of whether the oil is synthetic.
Rather, the risk to 45yr old engines from synthetics seems to arise from two related factors: synthetics may not be as good at preserving all seals, including valve stem, and especially old gaskets. 2. The greater detergent qualities in synthetics may excessively cleanse built up deposits around seals and gaskets that serve to minimize leakage.
As a risk-taker (otherwise who would buy a 45 yr old beauty with unknown engine history?) I am tempted to try Mobil 1 but only 15W-50 because the more viscous, the less leakage, always--and also it seems the silver cap normal rather than the gold cap extended life, because the latter apparently has higher detergent qualities due to it being intended to last 15k miles.
Theo Benz
66 230SL-she's a beauty
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Detergency in oils isn't like a bar of soap. It won't scrub your engine clean of all deposits leaving it sparkling clean. At best, it might remove anything that's loose but it shouldn't create new leaks. It could make an existing leak worse but that would depend on where the leak was and how bad it was leaking before the change. I don't think engine oil viscosity will have much impact on on leaking. Hot oil will leak out where ever there's a place that isn't sealed up properly.
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My understanding of detergents in oil is that they do not necessarily clean what is already stuck on the engine, but rather suspend the particles in the oil for the filter to trap. Non-detergent oil allows the particles to drop to the bottom of the reservoir.
That is why you use NON-detergent oil for engines without filters (lawn mowers, compressors, very old cars etc...) . You don't want the particles floating around in the oil. You want them to fall out in a sump and manually clean it out.