Ever wonder if it's time to change your oil? If it's been a while & you've done a lot of short tripping, or have a dirty engine your trying to clean up, maybe the Blotter Spot Test method is for you. It can give us an idea when the oil filter & engine oil has, or has nearly reached it's soot carrying load capacity, is saturated, or nearly so & dispersancy is failing & the oil & filter need changing.
http://www.machinerylubrication.com/...nt-dispersancy

 

A visual on how to interpret our oil analysis blotter spot test. http://www.enginecheckup.com/images/cf_gas_large.jpg