A tire's built-in tread wear indicator bars are flush with the surrounding tread. What does this mean?
- The tread is down to about 6/32 in. and the tire needs rotating
- The tire has been run overinflated and needs its pressure reset
- The tread is down to about 2/32 in. and the tire needs replacing
- The tire has a shifted belt and needs to be balanced again
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C. The tread is down to about 2/32 in. and the tire needs replacing
Wear bars are moulded across the grooves at 2/32 in. of remaining tread, the point at which the tire is worn out. They say nothing about inflation or balance; they only show remaining depth.
Reference: Tire tread depth; tread wear indicators
In the oil viscosity grade 5W-30, what does the '5W' describe?
- How the oil flows at normal operating temperature
- The weight of the oil in ounces for each quart
- The percentage of detergent additive in the oil
- How the oil flows at low (winter) temperatures
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D. How the oil flows at low (winter) temperatures
The number before the W is the cold-temperature (winter) rating; a lower number means the oil flows and pumps more easily on a cold start. The second number, 30, is the viscosity grade at operating temperature.
Reference: SAE J300 engine oil viscosity grades
What is the main reason for rotating tires at the recommended interval?
- To even out tread wear among all the tires
- To correct the wheel alignment angles
- To restore the balance of each wheel
- To reset the tire pressure monitor
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A. To even out tread wear among all the tires
Each wheel position wears a tire differently, so moving the tires around evens the wear and extends tire life. Rotation does not change alignment or balance; those are separate services.
Reference: Tire service; rotation