Warming up your car before driving is one of the best actions you can perform to reduce engine wear and extend engine life. This, alongside changing your oil, is probably one of the most commonly stated engine care tips, and yet, since there are many who do not understand the importance or reasoning behind this tip, I have decided to make this one of On-Site Auto’s first pro tip topics.
Here’s how it works. There is a reservoir of oil at the bottom of the engine contained in the oil pan. The oil pan collects the engine’s reserve oil and feeds it to a pump which pressurizes the lubrication channels throughout the engine. This powerful pump is capable of over pressurizing the oil channels and rupturing critical seals within the engine. To guard against this over pressurization, engines are equipped with a pressure relief valve that opens a bypass channel and returns the excess oil to the oil pan.
Although the pressure release valve may sound like an emergency protection plan, it’s actually in constant use. Every time the engine accelerates, the oil pump increases its output volume and you may notice your vehicle’s oil pressure gauge rise. If it wasn’t for the oil pressure relief valve, that oil pressure would continue to rise, causing severe engine damage. Also, whenever your engine is cold, the oil does not flow as easily due to higher oil viscosity, thus causing higher oil pressure. These two situations (high rpm and low temperature) are the main reasons the pressure relief valve is necessary. However, the necessity of the pressure relief system has its drawbacks, which brings us back to why you’re reading this.
When the engine is cold it gets the least lubrication. Let’s talk through a typical cold start. You start the engine, and the oil pump starts pumping thick cold oil through the engine to critical components. Even though the oil is cold and thick, the oil pump is capable of pumping sufficient amounts of oil to the critical engine components at low engine speeds (idle), and for the moment all is good. Then you put the car in gear and accelerate into traffic. At higher speeds the critical engine components start calling for additional lubrication, and the oil pump starts pumping more oil. However, the pressure relief valve responds to the excessive oil pressure built up by the thick cold oil and routes the additional oil that the components need back to the oil pan. Only at proper operating temperature can all the components work in harmony with each other and supply proper lubrication at driving speeds.
I hope this article has helped explain some of the ‘why’ behind an age-old car care tip. Next time you go out, let the vehicle warm up for a minute or two before you drive. Your vehicle will thank you with years of dependable service.