"Grimly Curmudgeon" wrote in message
...
It was somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember "top gear"
saying something like:

Oh he exists alright, and as Doctor Evil recommends use cheap supermarket
oil for 40,000 miles as you all know the answers, and would know this is
what is best.

Cheap supermarket oil has a place in the market - in SOCs that lose/use
a bit of oil anyway and aren't worth spending a lot of money on.

I use fleet oils of a decent standard in my cars, vans and bikes and
have done for years. If it weren't for the oil contamination inherent in
diesel engines, I would certainly use synthetics in them, but since I
wouldn't trust the extended drain interval recommended by Ford in the
case of my Transit (some 14,000miles), the benfits of synthetic will
continue to elude me. In that particular case I prefer the peace of mind
of simply changing oil and filter at 6000miles.

You see, I know all about synthetics and fully support their use where
appropriate; but your insistence that they fit everything is, to repeat,
misleading ********.

As an illustration...

One of my bikes had over 200,000 miles up on the engine when it lost
compression. A stripdown revealed the rings had past their sellby date
and had simply got a bit tired.
On inspection, I found the pistons and bores had no discernable wear on
them from new and could go together quite happily with new rings.

Oh, by the way, that engine was only ever run on mineral 20/50 all of
its life, changed every 2-3000miles, and worked hard, it being a
despatch bike.

What degrades mineral oil a lot is the camshafts. They put enormous pressure
on oil degrading it quite quickly. Once it looses its shear cam wear is
accelerated. Synthetics resist cam wear infinitely better than minerals and
for all of the time the oil is in the engine. With everything being top end
on an engine these days, on start up synthetics really benefit. Overnight
the oil drains down leaving the galleries and top end dry. The thin nature
of the oils means it gets to the bearings very fast. The cams are about the
furthest point away from the oil pump.

Synthetics are perfectly suited for diesels as they resist contamination
much better than mineral oils, and then all the other attributes which have
already been mentioned. Mobil make a Mobil 1 for turbo diesels, as do other
makers.

At the oil research lab I asked them about diesels and they also said
synthetics are better for diesels too. Now this was about 15 years ago, and
synthetics have come a long way since then too. They said one of the few
places for mineral oils was in slow revving ships engines, where the oil and
engine were up to temperature and oil pressure primed before the crank was
turned, but only if the oil was regularly tested and changed immediately on
degradation. Mineral oils degrade quite quickly once they go.

Cheap supermarket oil has a place in the market? That may be the case of the
"market", but not in any engine I know of.

Dropping the service intervals on a Ford is a good thing. Best not buy a
FixOrRepairDaily in the first place.



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