There are two basic types of engine oils-Regular and synthetic. Synthetic oil can be used in all cars, but regular oil cannot be used in cars which require synthetic oil.
There are two other factors which differentiate oil:
Viscosity: viscosity is a measure of the oil’s ability to flow. As the temperature drops, oil tends to thicken like molasses, and as the temperature rises, oil tends to thin-out like water. You need oil to flow through your engine when it is zero degrees outside and when it is 100 degrees outside.
Oil manufacturers added chemicals to their oil so the oil maintains a consistent viscosity through a wide range of temperatures. Oil companies label their oils, such as 5W30 or 05W20 so you/me know the viscosity. The automobile manufacturers require specific viscosity oils for their cars.
The lower number refers to the ability of the oil to properly flow at low temperatures, and the high number represents the ability of the oil to properly flow at high temperatures. It would have been nice if those numbers represented degrees Celsius or degrees Fahrenheit, but they do not. In Chicago a “5” as the lower number is adequate all winter long. In areas where the temperature gets well below zero, Valvoline makes a ‘0’ weight oil. In Chicago a ‘30’ weight oil is adequate for our summers.
For reasons not known to me, there are some cars which require 5W20 oils. Even though the upper number is ’20,’ these oils are fine for Chicago summers. The proper viscosity oil for car is always in the owner’s manual, and often found on the oil fill cap. Most of the time, but not always, if your car needs synthetic oil it will say so under the hood.
The last of the equation is the version of the oil. Oil companies have made tremendous advances in their oil. When there is a change it is indicated by the letter following the viscosity range. I don’t know the current letter. I don’t need to know since I buy Valvoline oil and they always bring me the latest version. The latest version can always be used in older cars, but you should not use older versions in newer cars. If you buy oil from any respectable retailer you will be getting the latest and greatest version. I point this out in the event a friend of yours offers you the oil which has been sitting on the shelf of his garage for the last 10 years. This ten year old oil, may not be the best for your car.
Other notes on oil:
The oil manufacturers add other chemicals to their oils. They add a chemical which isolates water. Without this additive the water would tend to cause rust inside your engine. They add an anti-foaming agent. Without this additive the oil would foam-up inside you engine. This might sound cool, but your oil pump cannot pump foam, it can only pump a liquid. And you would not be able to drive very long without being pumped insides your engine. They have also added friction modifiers to increase gas mileage.
Next week I will share with you why I recommend you change your ‘regular’ oil every 3,000 miles – and why the manufacturers might say something different, but add a weenie clause to their initial recommendation.