The Other Mike wrote:
On Thu, 08 Dec 2011 11:27:21 +0000 (GMT), "Dave Plowman (News)"
wrote:

In article
,
thirty-six wrote:
Really tight torlearnces and beter materials and beter design and
synthetic oils have pushed oil changes from 3000 miles (BMC A series) to
As fitted to the Marina, Maestro and Metro, the main service interval
(with 1980's oils) was 12,000 miles without any intermediary interval.
That was the A plus version. Not the same as the earlier A Series.

It was as near as dammit the same engine! That 12k servicing move imho
was a marketing decision, not one necessarily based on engineering.

Apart from the external ribbing on the crankcase fundamentally the
mechanicals were near identical to the earlier engines. They rolled
the fillet on the crank journals to improve fatigue life, and iirc
finished them a bit better.

The distributor changed to allow longer intervals before the points
needed adjusting (sliding point contacts) The crank damper got bigger
and there was minor work on the valve seats and combustion chamber
shape, carbs changed to integral float chamber SU's, plus a bit of
work on the crankcase ventilation. There was some other change, I
can't recall exactly what, on the cam drive - maybe the tensioner, or
getting rid of the rubber inserts on the chainwheels. The tappet
covers were also deleted to reduce oil leaks.

The biggest problem for any lubricant was on those with the transverse
engine when gears in the box mashed up the engine oil. Most burnt the
oil such that what was in the sump at 12k miles wasn't what was in the
sump at the last service


I honestly think that the change to service interval was about marketing
and better oils in the 70's.

The Germans and Japs had these service intervals and BL was forced to
follow their lead.

A whole BL car was pretty fecked at 70k miles anyway. And Ford weren't
any better.