Motor oil is the lifeblood of internal combustion engines and without it, an internal combustion engine won’t last for more than a few minutes without seizing up.
However, if you’re curious if a car will even start without oil, you’ll be surprised to hear that all cars start without engine oil every time you start the engine. If that struck your interest, keep reading to find out even more.
What Is the Purpose of Engine Oil?
There is more to engine oil that meets the eye because lubrication is not the only function that the motor oil performs, in fact, motor oil performs seven main functions.
Protection From Corrosion
The internal parts of an engine are also susceptible to rust and oxidation as they are exposed to oxygen and acids. To avoid oxidation and prolong engine life, motor oil is packed with corrosion and rust inhibitors that provide a thin protective coat, while also neutralizing acidic combustion byproducts.
Reduction of Friction
This one is rather obvious, but it’s the most important function of motor oil. The internal metallic parts of the engine are in constant contact with each other and its up to the motor oil to prevent that. Motor oil provides a fluid film that acts as a barrier between the internal parts of the engine, minimizing direct metal-to-metal contact, thus minimizing friction.
Cleaning and Washing
Partially burned fuel and other combustion byproducts will escape past the piston rings into the crankcase. These contaminants tend to adhere to engine components and form a sludge-like substance.
Motor oil maintains internal cleanliness by trapping the contaminants within the fluid and preventing them from adhering to internal components. In combination with motor oil possessing a degree of solvency, which assists cleanliness by dissolving solid, liquid and gas contaminants, motor oil contains detergents and dispersants. Detergents are additives that are responsible for preventing contaminants from adhering to internal engine components, while dispersants act as solvents and prevent sludge formation.
Engine oil lowers the overall temperature of the internal parts of the engine by reducing friction, as friction creates heat.
However, engine oil also absorbs heat into itself and transports it into a safe location, where the heat is dispersed, thus lowering and maintaining an even running temperature throughout the internal parts.
Sealing of Combustion Gasses
Unfortunately, the surface of the piston rings and cylinder walls will never be completely smooth. That’s where motor oil comes to save the day. By filling in these imperfections and creating a dynamic seal between them, combustion gases are kept in the combustion chamber, thus reducing blow-by and maximizing horsepower.
Engine oils have the ability to cushion mechanical shock, by absorbing and dispersing the energy spikes over a broad area. Because of these shock dampening properties, engine oil extends the operating life of the internal engine components.
Motor oil can not be compressed and is an excellent energy-transfer medium. Engine manufacturers often rely on motor oil to actuate variable valve timing components such as VTEC, and use motor oil in hydraulic valve lifters. Some manufacturers even used highly pressurized 3500PSI engine oil to pump fuel from the fuel injectors (HUEI injection).
What Happens If There’s No Oil in Your Car?
In short, the engine will seize up. Without the motor oil separating the metal-to-metal contact of the internal parts by a thin oil film, friction and heat will take over. The internal parts, such as main bearings, cylinder walls, and piston rings, will start grinding against each other. The increased internal friction will generate heat and boil the coolant, which will start steaming.
The heat and friction will rapidly increase until the piston and the cylinder walls reach a temperature high enough that will fuse them together, making the engine stall.
Here’s a great video by Engineering Explained, that shows what happens to an engine without oil:
How Long Will an Engine Last with No Oil?
How long will an engine run without oil and if it will seize suddenly or gradually depends on a lot of factors. In most cases, an engine without oil will run for at least 15 minutes before destroying itself, however, I’ve heard stories of guys getting a few hours of driving until their engine completely gave up.
Will a Car Start Without Oil?
As crazy as it sounds, your car’s engine always starts without oil at least for a few seconds. What do I mean by that? Well, the engine oil is a viscous liquid and it takes time for it to reach all critical lubrication points.
Have you noticed that once you start your engine, the oil pressure warning light stays on for a few seconds even when the engine is running? That’s because the lubrication system is still building oil pressure and the motor oil hasn’t reached all the lubrication points. It takes even longer for the engine oil to reach all critical lubrication points on cold days.
This is completely normal and it’s the reason why most engine wear occurs during the first minutes of running the engine. That’s why you should avoid revving the engine right after start and let it warm up a bit, however, that’s a different topic for another day.
Even though motor oil is vital for internal combustion engines, car engines will definitely start without oil and they do it every time, before reaching the required oil pressure. They, however, will not last long without engine oil.
Hopefully, now you have a better understanding of the importance of engine oil.
Eddie is the co-founder of CarCareCamp.com, and the site’s primary contributor. Automotive repair has played a major role in his family for generations and he’s determined to continue the legacy further on. Under his belt, Eddie has a bachelor’s degree in Automotive Electronics Engineering and almost a decade of experience working as an electrician in a major semi-truck dealership in Europe.