I am aware that various oils and lubricants for mechanical things (like cars, for example, but lots of other machinery) come in various weights and viscosities, all of which have a preferred range of temperatures.
So… what happens if the various oily/greasy things are NOT operating in their preferred temperature ranges?
I’m guessing that if conditions are too cold the lubrication gets thicker and does not reduce friction nearly as well. I suppose if things really get chill it could even solidify, thereby rendering the machine unmoving.
But what if things get too hot? What happens then? I suppose if things are extreme enough the lube could boil off, but what if it’s not that bad?
Eagerly awaiting the answers during this heat wave.
You are correct on the cold side. In places like Alaska, if the engine doesn’t have a block heater and it gets cold, the oil turns into a thick syrup. The electrolyte in the battery will freeze too. That car ain’t goin’ nowhere until someone heats it up. If you manage to get the engine to crank (maybe you took the battery inside to heat it up for example), that thick oil won’t circulate very well and the lack of proper lubrication will cause damage to the engine parts.
Even at Alaska temperatures (-40) the oil won’t freeze, but it will be thick enough to cause problems.
When engines overheat, usually something other than the oil will give out first. Head gaskets tend to fail, the engine heads warp, etc. The engine will also misfire and stop working, and the engine will often boil off its remaining coolant. You can completely ruin the engine at temperatures lower than the breakdown point of oil. The pistons tend to expand faster than the engine block, so often you’ll end up ruining the piston rings, severely scoring the inside of the pistons, and the pistons could even get stuck, which could really cause some severe damage.
That’s not to say that oil can’t get overheated, because it can. Once the temperature gets hot enough (typically somewhere between 300 and 500 deg F, depending on the type of oil) then the oil will start to break down. When this happens, the oil gets too thin to be useful and the parts lose their lubrication and get damaged. Additives in the oil can boil off, and then you have these additive gases blowing around inside the engine. As you can probably imagine, oil with gas bubbles in it doesn’t lubricate very well either. The oil’s surface tension starts to decrease as well, meaning that the already thin oil no longer clings to parts as well, again further reducing lubrication.
The engine is probably going to be completely toasted long before the oil completely boils off. If you manage to get the oil above about 550 to 600 deg F or so though you will get it to boil.
Synthetic oils break down at a higher temperature than conventional dino oils do.
In addition to that information about engines, what about non-engine mechanics? Do hydraulic fluids in heavy machinery have specific temperatures ranges? What about lubrication for mechanical joints/hinges/etc? How much of an issue is it for machinery working in, say the Alberta oil sands in winter? Or Dubai construction machinery in the summer?
I’m also guessing that anything designed to work in outer space is going to face some unusual environmental conditions as well, not just temperatures but pressures (or lack of them) as well.
Industrial hydraulic systems typically try to maintain the fluid in warm conditions. I’ve run systems where 30-40C is the preferred range. Speed and pressure controls were set to handle the oil at that viscosity. Coolers and heaters were added to maintain it. High heat or cold applications used different types of oil and they have there own preferred ranges. It all comes down the the viscosity of the oil and the types of additives to determine the operating temperature range. Your car maybe has a transmission cooler near the radiator and A/C cooler.
On a fully charged battery the electrolyte will be able to take more than -60F without freezing. The Cr(Bucyrus Erie Power shovel)
anking amps are very significantly reduced and any attempt to start will result in a frozen battery very quickly if it isn’t immediately recharged!
So charge or jump 1st off in extreme cold.
Most oils do better in high temp environments than in extreme cold. in cold a hydraulic system may never reach a optimal operating temp all winter long! This will cause filtration systems to bypass or even damage filtration media.
Also pump cavitation will cause damage to pumps.
If your thread is in regards to a car in extreme temps like you are describing your engine cooling system will fail before your lubrication oils fail and you will experience everything ECG covered in post #2.
I remember standing on solidified gear oil during rebuilds on large excavators
Too low of a temperature I dont see being of much concern. After you get the machine started of course! It may have some weissenberg effects in some applications like drilling fluids but once friction and/or combustion add heat, it would overcome any ambient temperature effects. There could also be pumping issues that could occur or for a grease if you get too cold and reach the glass transition temperature it would just shear into rubble.
When a lubricant gets too hot naturally the viscosity decreases. Anytime you add more heat to a system oxygen gets more ammo to cause havoc. Once you leave the specified temperature range polymerization and sludge can begin to develop ata much faster rate.
Check out some reading on tribology. That field specialized in lubrication and wear. Its either greek or latin for the study of flow
I once worked on an aircraft that took a special grease for the stabilizer trim motors. Fools would use the same grease used on the most of the other lubrication point on it. At higher altitudes it’s well below zero degrees. The trim motors would freeze up due to the grease and the pilots would have to hold on to the yoke manually flying the aircraft usually until it landed. The pilots would be MAD.
I actually don’t want to focus too much on cars, I’d like is as a more general information thread. Cars are handy to talk about because they’re machinery almost everyone is familiar with to one degree or another but they aren’t the only machinery
Cold temperatures = too thick, even solid, and perhaps ice (absorbed water forming solid water.), which can cause blockages. So it works and runs some part without any lubrication. Or it just jams one part.
heat - hot oil/grease produces a smoke, its as if evaporating , but its also decomposing. So its not lubricating properly and the engine loses power… valves don’t work properly and more power goes to driving the metal on metal friction … The decomposing means that there may be carbon deposits on surfaces, and carbon crystals in the oil that scour like sandpaper (or diamond dust paper), and the oil is no longer the spec it was before being overheated, and has to be changed. Otherwise it may well build up more and more carbon deposits, and sludge, a thick greasy paste of carbon and grease. Sludge forms as the detergents are destroyed by high temperature ,and there is more to be a detergent to as the oils molecules were affected (decomposed, broken down) by the high temperature. The smoke off the hot oil is flammable, and can be ignited by a slightly higher temperature.
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apilot frind of min had this happen to him on a cost to coaaaaaast f anddddd and he applied manual trim all theway with his feet up on the panel anee a firm a fitm lean bank in to his seat.in hiddrgglight