Can spark plugs really go 100,000 miles before being changed?

Improvement in spark plug technology does allow for some styles of plugs to function properly for 100,000 miles.  Check with your mechanic to verify the correct spark plugs and expected mileage before requiring replacement.

How do you know how much air to put in tires?

Tire pressures are normally listed on the tire label found inside the driver’s door on most vehicles or the owner’s manual.  Tire and auto manufacturers also have suggested tire pressures available on-line.

Will putting radial tires on an older car that came with bias-ply tires hurt its suspension?

Radial tires installed on an original bias-ply tire vehicle will not hurt its suspension.  The handling and ride characteristics of the vehicle may be changed depending on the quality of the replacement radial tires.