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basjoos · 06-16-2011, 08:20 AM

The thing that normally wears out in motor oils is the residual alkalinity. Motor oil starts out with a pH of 9 to 10 and then it gradually drops in pH as acidic combustion byproducts gradually accumulate in the oil. Eventually these acidic byproducts use up all of the pH buffering agants in the oil and and the oil pH drops. When the pH gets below 6, the oil needs to be changed since its acidity then starts corroding the inside of the engine. So you can check the oil's pH and change it when it goes below 6.

06-16-2011, 08:20 AM	#10 (permalink)
basjoos Master EcoModder Join Date: Dec 2007 Location: Upstate SC Posts: 1,088 Aerocivic - '92 Honda Civic CX Last 3: 70.54 mpg (US) AerocivicLB - '92 Honda Civic CX Team Honda 90 day: 55.14 mpg (US) Camryglide - '20 Toyota Camry hybrid LE 90 day: 65.83 mpg (US) Thanks: 16 Thanked 677 Times in 302 Posts	The thing that normally wears out in motor oils is the residual alkalinity. Motor oil starts out with a pH of 9 to 10 and then it gradually drops in pH as acidic combustion byproducts gradually accumulate in the oil. Eventually these acidic byproducts use up all of the pH buffering agants in the oil and and the oil pH drops. When the pH gets below 6, the oil needs to be changed since its acidity then starts corroding the inside of the engine. So you can check the oil's pH and change it when it goes below 6. Last edited by basjoos; 06-16-2011 at 09:44 AM..