What could happen if someone doesn’t let an engine warm up?
In: Engineering
I found this…
*When an internal combustion engine sets overnight the mechanical components will be cooler than when at “ideal” operating temperature. Engine wear is most experienced at cold start due to the lack of oil available to engine components. The dimensional tolerances will be at the non-ideal design limits. Maximum clearances in all bearing and piston to wall specifications. The piston will be an oval shape having not expanded to true oval for minimal clearance. Some piston slap will cause some wear on the piston skirts until thermal expansion maximizes. No lubrication oil will be top side or on the cylinder walls. This is where the most “wear “ occurs. Metal to metal and no lubrication. Why? The oil pump galleries may be dry with no oil present. Today 99% of the cars on the road use mechanical oil pumps. This means the pump oil pump cannot deliver oil pressure until it has sucked up the oil from the oil pan sump and has begun pushing the oil through the oil galleries. From cold start until the engine warms up and the oil fills all the oil galleries and we have a steady oil pressure reading we do not have proper lubrication. It was true that we suffered a lot of cylinder / piston wear about 20 years ago. The cylinder walls used to be honed and finished with many peaks and valleys remaining in the surface profile. The introduction of Plateau Honing meant the peaks were knocked down on final hone pass so the engine break in time was a lot shorter and we had significantly more valleys to retain oil. Todays computerized fuel monitoring means we do not have excessive fuel splashing on cold cylinders at start up unlike the day of the “choke”. Your assumption that ”thicker oil” does better lubrication is not true today with the introduction of synthetic oils. Cold start lubrication is best achieved from an oil with good cold flow Properties. The reason the 98C wear is the least is the engine is functioning properly. At 20C the engine is way too cold and piston rings are permitting too much blow, washing the lubricating oil off the cylinder walls. The piston is not thermally expanding for a tight piston ring seal. When the oil is not heated to proper temperature harmful deposits, moisture, and acid accumulate rapidly, then eat away at the inside of your engine. There is a lot of chemical things happening during the combustion process so you must change engine oil at least every 3 months regardless of the miles driven. You literally have acid and sludge developing in the crankcase.*
Latest Answers