Quote:
Originally Posted by MetroMPG
Do the problems exist in both synthetic and mineral oils? I don't know enough about the separation issue, but synthetics seem to have resolved the viscosity problem for cold weather/cold start performance.
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No, but still sort of...
Sorry! Engineers never answer in clear yes/no.
Synthetics contain no paraffin, so they don't need pour point depressants. So, they don't have the separation problems. Also, they tend to have dramatically lower pour points, period. That is, they stay liquid at much lower temps than conventional petroleum motor oils.
But there are some downsides. For example, although the oil itself doesn't tend to break down into individual components, lots of the crud it can be carrying does. And since the synthetic oil doesn't thicken with temp, you can get something called 'thermal collection'. Basically, if it is cold enough, the gunk can fuse into bigger, nastier hunks of gunk.
If you use synthetic to greatly extend intervals between changes, this can be a real concern on some engines. In that case, the obvious answer is use synthetic for the low temp viscosity, but still do regular oil changes to keep the system clear of excess gunk.
If it wasn't clear above, I'm not really disagreeing with your basic point. I'm just stressing that prevention is a lot easier on engines than recovery.
I'm also thinking about my daughter. Having a car sit outside in the coldest part of winter in Minn. undriven for 4-5 weeks is a very real possibility. A jump and a block heater may get it started, but I've already changed out one cyl and would prefer not to do another any time soon - so I lean towards over cautious.
-jjf