Frequently asked questions
Get answers to basic questions about motor oil and specific Mobil™ products.
Thanks to advances in engine technology, today’s cars are exceptionally reliable and can go much further between services than earlier models, often thousands of miles further. Of course, that’s good news for you. But it does mean that it’s more important than ever to check your oil level regularly and top it up when necessary. If you don’t, you’re taking a real risk with your engine’s health. As the oil level drops, the remaining oil in your engine has to work harder, becoming dirtier and wearing out faster with the result that your car’s performance will start to suffer. Not much further down the road, your engine will be in real danger of increased wear, overheating and even total seizure.
Ideally, you should check your oil weekly, as recommended by most car manufacturers. If the oil level drops from maximum to minimum after less than 1,500 km, you should have your engine checked. Oil consumption is different from one car to another and from one driving style to another.
- Park on a level surface, turn off the engine and wait for 3-4 minutes to allow the oil to settle.
- Find the dipstick, pull it out, wipe and re-dip before taking your reading.
- If it is less than maximum, check the fill guide to find out how much you need to add.
- Remove the oil filler cap on top of your engine, add the right amount of oil and replace the oil filler cap after the oil top up.
- Wait 60 seconds to allow the oil to drain into your engine, then re-dip to check the new level. Add more oil if necessary and replace the oil filler cap.
Motor oil breaks down over time. When it breaks down, it loses its effectiveness and can no longer properly protect your engine. In addition to lubricating an engine's moving parts, motor oil is designed to carry combustion by-products away from the pistons and cylinders. It is designed to deal with the small amounts of water that form as the engine heats and cools, and to collect the dirt and dust that enter the engine through the air-intake system. It also handles acids that are formed by the reaction between water and other contaminants. Sometimes there are even fuel leaks (fuel dilution) or coolant leaks that get into the oil system.
As a car is driven, the level of contamination in the motor oil constantly increases. The oil filter removes particles as the oil passes through the filter, but over time an oil's additives are used up and the oil itself can start to degrade (oxidize or thicken). At that point, the oil can no longer do its job and must be changed.
The rate at which contamination and additive depletion occurs depends on many variables. One of these is driving conditions, which vary greatly and have a direct effect on the useful life of the oil. Other factors include the precision of ignition, fuel injection or carburetion adjustments, air cleaner service and the general mechanical condition of the engine.
Oil should be changed before the contamination level reaches the point where engine damage can result. Because it is difficult for the individual motorist to determine when the contamination level is too high, automobile manufacturers provide recommended oil change intervals. These change recommendations vary by model year and manufacturer. Recommended intervals and mileage limits also vary with the type of service under which a car operates. More frequent oil changes are recommended for severe service.
Engineers work to establish an optimal viscosity for an oil, based on load and speed conditions. They balance lighter – or low-viscosity – oil, which provides little resistance to motion thereby saving fuel and efficiently transferring horsepower, with a heavier – or high-viscosity – oil that resists being squeezed out of the contact area between metal surfaces.
The complicating factor is that the viscosity of an oil varies with changes in temperature – thinner when hot, thicker when cold. At low temperatures, we need the motor oil to flow readily (not thicken too much or gel). At high temperatures, we need the motor oil to keep from becoming too thin and allowing metal-to-metal contact. Therefore, engineers developed multigrade motor oils.
Viscosity is a measure of a fluid's resistance to flow. A fluid with low viscosity flows easily and is often called "thin." Water is an example of a fluid with a relatively low viscosity. A fluid with high viscosity is often described as "thick." Maple syrup is an example of a fluid with a relatively high viscosity.
Your oil warning light can come on for a number of reasons including: Low oil level, a failing oil pump, a faulty oil pressure sensor, blockage in the oil system, excessive foaming of the oil and more. In all cases, you should shut down your engine as quickly as it is safe to do so. Continuing to operate your engine with low oil pressure can result in serious engine damage.