Can you imagine driving down the highway what would happen if the oil quit flowing inside your engine? If the motor oil couldn’t get through your oil filter. We put a lot of confidence in one little bulb lighting up to let us know we may have an oil problem. Disaster happens fast at 2100 rpm and highway speeds!
When oil stops flowing to the engine you lose critical lubrication and cooling. Catastrophic seizure is imminent.
Oil filters are designed to handle so much contamination loading before they need to be replaced. I say designed loosely because I think most companies just pleat the paper media jam it in a can and call it good. I personally want more for my engine.
Anyway it the paper or synthetic media does get blocked oil filters have a bypass valve which is spring loaded. This bypass valve opens at a specific pressure differential that varies between vehicles. If the media does get overused and blocked then oil will flow through the bypass valve. The problem with that is the oil is no longer getting filtered.
Sometimes this will show up as an oil light indication that there is low oil pressure downstream of the filter (hopefully your oil filter bypass valve is not stuck!). I can guess that sometimes the pressure decrease is not enough to cause an oil light indication.
The bypass is also prone to open on startup when your motor oil is cool and thick. The pressure drop through the filter media is too high to pass all the thick oil and some has to go through the bypass filter. Again this causes unfiltered oil to pass up into the engine. Don’t worry too much though it has been like this for years and engines have done pretty well.
The problem occurs when an oil filter is not changed for extended periods of time and becomes blocked for long periods of time. Unfiltered motor oil can then continuously circulate through your engine and cause unnecessary wear.
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