You see those cryptic combinations of letters and numbers on motor oil bottles everywhere. What do they mean? To decipher them, you have to understand viscosity. Viscosity measures how much the motor oil can resist flow. In other words, if you tip a motor oil bottle over, how fast it spills out indicates its viscosity. The more viscous, the slower it moves.
To indicate viscosity, the SAE (Society of Automotive Engineers) developed a standard scale.
- 0W is thinnest ("W" stands for winter)
- 60 is thickest
The recommended multi-viscosity oil you use in your vehicle is usually good all year round because it can respond to a range of temperatures. That's why you see two numbers on most oils.
For example: 10W30
This means the viscosity is at 10W when the engine is cold and 30 when the engine is hot.
Low viscosities are good for cold temperatures (hence the "W" association) because the oil is thinner. Thinner motor oil flows more easily and moves quickly. When you start a cold engine up again, motor oil needs to travel to the top of the engine, where it trickles back down. Since motor oil is vital to lubricating your engine, it needs to move quickly and low viscosity helps it do just that.
When your engine heats up, higher viscosities mean the motor oil won't thin out too much and will keep parts separated by a film of oil. So your motor oil is always maintaining a delicate balance: it needs to flow well when the engine is cold but also retain enough body at higher temperatures to keep metal parts lubricated and separated.
To find out what motor oil grade is right for your vehicle, check your vehicle's owner's manual.
Octane. You see the word every time you visit the gas station but what does it mean? Octane ratings measure fuel's ability to resist engine knock. Engine knock is caused by fuel being ignited by something other than the spark plug.
If you are using an octane grade that is too low for your vehicle, something other than the spark plug can ignite the fuel in the engine. The engine could even get hot enough where the fuel explodes by itself.
What octane does your vehicle require? Check your vehicle's owner's manual. Don't upgrade to more expensive octane ratings unless your manufacturer recommends it.
When your check engine lights comes on, you may be torn between utter panic and just wanting to ignore it and hope it goes away. That's perfectly understandable. That same check engine light could come on for anything from a serious engine or transmission problem all the way down to a loose gas cap.
Some people are confused by charges for diagnostic services for a vehicle repair, even though many other services in life include diagnostic fees – things like computer service and appliance repair are just two examples. Even when we go into the doctor for a medical problem, we're paying her to diagnose our ailment and of course for the tests that go along with it. So receiving a diagnostic charge for a tricky automotive problem shouldn't be a surprise.
How important is wheel alignment?
Think of it this way: Research indicates that the average vehicle is driven about 12,000 miles per year. A car with a toe angle misadjustment of 0.34 degrees (only 0.17 inches) out of specification will drag the tires sideways for more than 68 miles by the end of the year!