[A/S] Synthetic Oil change interval and Oil change monitors

["Carol and Oliver Filippi" <ofilippi@xxxxxxxxxxxxx>]

I would be very suspicious of the latest "oil change monitors" which tell
you when to change your engine oil.

I believe these devices are simply optical devices which evaluate how dirty
the oil is based on the amount of light which transmits thru the oil sample.
( Some new clothes washing machines and dishwashers use this same concept to
determine the length of the wash cycle.)

The real question is, "Is this light transmission reading  a good measure of
the condition of the oil?" I personally don't think so, though I have no
scientific data or research to back up my opinion.

Heavy truck  (diesels which have large capacity crankcases - and large oil
coolers)   operators frequently test the oil prior to changing it.  The
maintenance people take a small sample of the oil and send it to a lab which
analyzes it for various forms and varieties of metal particles and chemical
contaminates to determine if the oil is in need of replacement.  Obviously,
this would very likely be beyond the scope of an on board computer chip
(though eventually such technology will probably be available).

The problem with determining when to change a synthetic oil (or any oil for
that matter) is to determine 1) when its lubricating qualities have
deteriorated to an undesirable level or 2) when the chemical contaminates
(blow by and other byproducts of combustion) have reached an unacceptable
level.  Either factor is cause for an oil change.  Note that extending the
oil change interval because the oil is still lubricating well may not be a
good idea if excessive acid buildup is eating the engine.  Don't ever forget
that these optimistic extended oil change intervals are brought to you
courtesy of the marketing department - not the engineering department.
These are the same folks that recommended lower than optimal tire inflation
pressures because the vehicle would "ride softer".

Don't ever forget that oil is cheaper than metal.

There is no question that a good synthetic oil has far superior lubricating
qualities and viscosity stability over a wide temperature range compared to
petroleum mineral oils.  In fact, they are such good lubricants that they do
not allow an engine to break (wear) in.  For this reason, a good approach
would be to run a new engine on conventional oil for the first 6,000  to
8,000 miles before switching to synthetic. [Contrary to the factory
installed Mobil 1 Corvette, etc.]

Synthetic oils have been used for many years with great success on heavy
duty piston type air compressors.  Here, the compressor manufacturers
recommend synthetic oil, but only after an initial "break in" with
conventional oil.  The life of the compressor is greatly extended by using
synthetic oil.  In addition, the oil change intervals are extended
significantly.  However, air compressor crankcase lubricants do not have to
deal with acidic byproducts of combustion (which one finds in a gasoline or
diesel engine).

Oliver Filippi