Ask A Scientist© Environmental Science Archive

Author:     cegrubbs
Text:       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?

Response #: 1 of 1
Author:     Eric Dallman
Text:       No, using synthetic motor oil will not reduce your auto emissions. 
The exhaust gases are gasoline combustion products, not the products of oil 
break down. Even if your car burns a lot of oil, refined oil and synthetic oil 
produce the same pollutants when burned. I would have to say that synthetic 
oil is not worth the extra cost. If I were to use it, however, I would change 
my oil and filter every 3,000 miles or 3 months (just as I do with refined 
oil). Your best bet is to make sure whatever oil you use meets your car 
manufacturer's specifications (listed in your owner's manual) and to change 
the oil at the intervals above (these are meant to increase engine life not 
reduce pollution). To reduce pollution your best bet is to take your oil in 
for reclamation. Approximately 450 million gallons of used oil are disposed of 
annually on the ground or waterways, landfilled, or burned in non-energy 
recovery incinerators (this includes crankcase, transmission, 
two-cycle/aircraft, and industrial oils). Also, if you change your own oil and 
have not heard this before you should note that used motor oil may cause skin 
cancer if repeatedly left in contact with the skin for prolonged periods. This 
is unlikely unless you handle used oil daily, but you should still wash any 
used oil off your skin as soon after handling as possible (using only soap and 
water, not ridiculous scrubbing techniques).