Well, I thought I'd put my two cents worth in on this synthetic oil debate.
A mechanical engineering friend of mine explained to me a few years ago that...
Regular oil in a car does a couple of things...
1. As expected, it accumulates dirt and other crud...hence the oil filter.
but more importantly,
2. As it absorbs elements of combustion (nitrous oxide and all that stuff)
it changes acidity. As this happens, it begins to break down AND attacks
the engine surfaces.
Number 2 is the reason manufacturers list both a mileage and time factor
(eg. 3 months) for recommended change intervals. This is also the
reason why you really should change the oil BEFORE putting your car into
storage for the winter. (I found out the hard way that the same is true for
brake fluid after I left my car in extended storage for a coupla years....the
master cylinder got rusted out due to moisture in fluid).
Synthetic oil apparently addresses the problem of number 2 above. It does
not break down and the acidity level is constant. So, the only problem left
is filtering. If you get a really good micron sized filtering system, you
really can wait 100,000km plus between filter changes --> although I haven't
heard of this done on MGs. The big problem with putting synthetic oil in an
old car is that the damn stuff is too slippery. If you have the slightest leak
in any of your gaskets, ;-) it will find a way to seep out.
I may have misunderstood my friend, so feel free to correct me if I'm wrong.
Cheers,
Phil Hunt, '74B
Kingston, ON
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