On 01/07/2018 12:12, Dave Plowman (News) wrote:
In article ,
Jim K wrote:
Istr the official "fully synthetic oil from new" regime has been
implicated in this excessive oil consumption. Something to do
with the piston rings not getting a chance to bed in
properly.

Synthetic oils were developed to extent oil change intervals. If they
stopped piston rings bedding in - which is basically wear - they'd also
stop other bits of the engine ever wearing out.

The *big* difference with synthetics is that because they don't contain
such a variety of molecules as mineral oils, their oxidation performance
is better. So they last longer at higher temperatures. Bedding in is
influenced by by boundary lubrication. This comes from the anti-wear
additives like ZDDP in either mineral or synthetic lubes. Mineral oils
often have enhanced boundary lube properties because they contain fatty
acids (as impurities) which, if you like, are nature's anti wear
additives. Automotive lubricants (whether mineral or synthetic) are
fairly highly "engineered" to optimise their properties (because the car
manufacturers specify the required performance for a given engine).
Further down the market, the effectiveness of things like 3 in 1 is
almost certainly partly down to the fatty acids. (This product also
contains effective anti-rust additives, which I suspect are responsible
for the distinctive smell, although I have never managed to find anyone
to confirm that).

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