Synthetic Engine Oil
Country: United States
Date: July 2006
Does using synthetic motor oil
lessen auto emissions? Is it worth the extra cost?
If you were to use it, how often would you change
the oil and filter?
Syntetic oil will do nothing whatsoever to lessen auto
emissions, as compared to a high quality standard motor oil.
In any properly working motor, the oil never gets anywhere
near the combustion process, and it is combustion that
creates the emissions.
The main advantage of synthetic oil is that it is slower to
break down than normal oil, and therefore the time between
oil changes can be longer. Also, some of the chemical
breakdown that oils suffer from, is not the oil itself
breaking down, but their additives such as "viscosity index
improvers" degrading. Synthetic oils need less of these
additives, so they suffer less from their breakdown.
How often should you change the oil and filter if one uses
synthetic oil? You ALWAYS change according to the vehicle
manufacturer's recommendations in the owners manual. Since
each manufacturer has specific instructions, I cannot give
you a general answer. As a rule of thumb, it is often
considered safe to extend the oil change interval by 50% with
synthetic oil, but again, you do what the vehicle
manufacturers says to do!
As for the filter, it should be changed at the same interval
as when normal oil is used. The filter's job is to filter out
abrasive particles that mainly result from the combustion
process. The type of oil has little to do with the formation
of this particulate matter, so switching to a synthetic oil
will not do anything much to reduce amount of particulates
that the filter has to filter out.
Now, is synthetic oil worth it? Perhaps. Synthetic oils do
not protect the engine better than normal oils. They just
last longer. So if, for example, a synthetic oil lasted 50%
longer than a high quality normal oil, and cost only 30% more,
then I would say it would be worth it in that case. However,
often, this kind of analysis shows synthetic oil cost more in
the long run.
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Update: June 2012