Undercoat or oilspray?

winter is comming and as i just got my car in the summer and every other car i have ever owned has been like 10 years old and already rusty, i never cared but now i want to protect my car and i dont know what i should do.. ive heard that undercoat can trap rust in and tottaly mess up your car is this true? ive got some oxizidation under my car in a few little areas and i woulndt say its rust, just normal colour for metal that is like 5 years old.. so my question, would you guys recommend oil spray or undercoat??

-shaner