Hi...
I have 2002 Sonata.. Which type of oil is required/good for oil change? thanks.

 

What does your owners manual say? My 05 Elantra manual recommends SAE 5W-20, 5W-30, or, above 0°F(-18°C), SAE 10W-30

 

Hyundai originally required a minimum American Petroleum Institute grade of "SE" for the car. Look for oils with the API rating seal on the bottle, all will likely have a grade of "SM" which exceeds specifications for the car. If you are changing the oil on a regular basis at 3,000 to 5,000 miles, any conventional oil with the API rating will do just fine. No need to spend money on more expensive synthetics or synthetic blends. Most new cars come with 5W-20 viscosity to improve milage, but a 6 year old car like yours likely came with 5W-30 in the crankcase.