age actually matters very little for a tire. The only frequent problem related to age is dryrot, you will see small cracks start to develop between the treads and/or on the sidewall of the tire. This means you should probably replace them but is actually caused by exposure to the elements and not solely age. Keeping your car in a garage will help prevent this problem. Obviously also if the tread is worn out from mileage they should be replaced.
No, your speedometer will be off and power and fuel mileage will be adversely effected.
The age is not a factor it is the mileage on the tires that matters. Go back to where you bought the tires and deal with them.
In the average truck that does not haul large loads the tires should be replaced every 40 thousand miles. This is the best way to ensure that your tires are giving you the best gas mileage.
Yes, in fact, rotating and replacing tires regularly is essential for maintaining your car's optimum gas mileage.
You change tires when they are worn out, not at a set mileage.
It is recomended that all four tires are the same age, same size, and same brand.It is recomended that all four tires are the same age, same size, and same brand.
definatley.
Yes.
yes
Fragmented question?? If you have under 3/32nd's remaining on your tires replace them. If you have wires hanging out of your tires replace them. Replace tires as needed or rather replace all at once if you do not like mis-matched tires. However many people will replace just two tires at a time then rotate when the other two need replacement.
Yes, the tires will ruin your gas mileage overall. Bigger tires weigh more and they're harder to rotate on the vehicle even though they gain greater traction.
Replace the spark plugs and air filter. Inflate the tires to specification. Idle less, accelerate easy, drive at a slower speed.