On Fri, 21 Oct 1994, Doug Phillips wrote:
> On the thread about TD engine lubrication:the best advice I've received is to
> run straight 30, non-detergent/non-synthetic oil. It gives me about 70
> psi cold at around 3,000 rpm, 50 psi when the motor is warm. I change
> it twice a year, once with a filter. It might be my imagination, but it seems
> my TD leaks/consumes less oil than most I've encountered. Could be attributed
> to a professional engine build-or frequent oil changes. I've also noticed the
> oil stays much cleaner after the SU's were rebuilt again (the first rebuilder
> did a poor job). I suspect the rich running carbs polluted/thinned the oil
> before the second rebuild.
Are you sure it's non-detergent? Non-detergent motor oil is almost
impossible to find these days, for the very good reason that it's not
recommended for use in _any_ engine (unless you _like_ sludge and
varnish). Anyway, whether or not it's detergent oil has no effect on oil
pressure, since the addition of detergents has no effect on viscosity.
The use of SAE 30 instead of a multigrade oil isn't a good idea. True, it
keeps your oil pressure higher, but that's a false sense of security.
High oil pressure isn't what keeps an engine from weearing. Oil flow is,
and SAE 30 doesn't flow as well as a multigrade when the engine is cold,
which is when the worst engine wear occurs. It's been demonstrated over
and over again that any engine (including your TD's XPAG) will last longer
with a multigrade oil. I'd recommend SAE 10W-40 in cold weather, SAE
20W-50 in hot weather. Those grades have proven to work well in the XPAG.
Change the oil every 3000 miles or every six months, which ever occurs
first.
If your engine is in good shape it will maintain satisfactory oil pressure
(around 50 psi for the XPAG) with multigrade oil. If it doesn't, then you
need to look for the cause rather than try to boost it with an otherwise
undesirable type of oil. The most common reasons for pressure loss in a
freshly rebuilt XPAG like yours are:
o Excessive crankshaft bearing clearances due to incorrect grinding of
the crankshaft journals.
o Excessive rocker arm bushing clearance due to over-reaming of new
bushings, or failure to replace worn bushings, or failure to replace a
worn rocker shaft.
o Failure to rebuild a worn oil pump, or to replace the bypass springs,
balls, and seats if the pump itself isn't worn beyond specs.
-----------------------------------------------------------------------
Chip Old 1948 M.G. TC TC6710 NEMGTR #2271
Cub Hill, Maryland 1962 Triumph TR4 CT3154LO (daily transportation)
feold@umd5.umd.edu
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