"The most obvious point to consider when temperatures dip very low is your choice of motor oil ... and filter," said Ramon Nunez, spokesman for Purolator Filters NA LLC.
Oil that's too thin, explained Nunez, will not provide sufficient protection for your engine. Oil that's too thick will keep your engine from starting in cold weather because the thick, gooey oil challenges your battery and starter motor to spin the engine fast enough for it to fire. So, check your owner's manual and choose oil viscosity accordingly.
"However, many people are surprised to learn that winter weather also puts extra demands on your oil filter," Nunez said. At 20 degrees Fahrenheit, most oils have the thickness of maple syrup. So when your engine first starts up, your engine's oil pump forces cold, thick oil through all the passages in your engine, including those in your oil filter. A number of factors determine if the oil will find its way through the filter to provide lubrication to your engine, while particulates are filtered out.
Nunez points out three specific design elements engineered into filters that help them perform properly in winter weather:
Structural integrity: On start-up in cold weather your engine will experience an initial surge of pressure. This pressure could compromise oil filters at their weakest point and could manifest itself as a blown-out sealing ring, a split crimp, or even a burst canister. Any of these can cause catastrophic engine failure. According to Nunez, premium oil filters like Purolator's PureOne are built and tested to withstand virtually all real-world pressure spikes.
Internal valving: Purolator engineers have developed a special spring-loaded bypass valve so that, if the filter goes unchanged for an extended period of time and is blocked with debris, unfiltered oil can flow to the engine, providing at least some lubrication – albeit with dirty oil. Instead of a reliable coil spring, some filter manufacturers may scrimp by substituting "spring" steel that may not return to its original shape after cycling. The result can be unfiltered oil for as long as the filter is in place, with potentially catastrophic results.
Filter media: Finally, most important, the filter must remove the smallest particles while offering the least resistance to oil flow. According to Nunez, Purolator's top grade PureOne filter has been developed to hold as much as 13 grams of debris, the equivalent of 31 standard size paper clips, while still providing minimal resistance to oil flow.
So, treat your car to fresh oil and a new oil filter in winter. It takes only a few dollars, but the life you save may be that of your engine.