Maintaining spark plugs is important for engine efficiency and performance. It is recommended to replace spark plugs on vehicles made before 03/2007 after every sixty thousand miles, while those with platinum spark plugs have a longer life span. Use the correct type of plug to maintain the right condition of the spark plug as well as a healthy engine. Remove Ignition cools and engine covers; clean all debris from Spark Plug Recesses before pulling out old plugs. To avoid damaging them, use an extension bar and a spark plug socket through which they should be unscrewed slowly without much force on ceramic insulators. Find Engine Condition Indicators On Each Plug Such As Deposits On Insulator Nose: Weak Mixtures Shows White Clean Insulators Or Too Hot Plugs While Hard Black Deposits Represent Rich Mixtures Or Worn Out Engine Parts; Correct Mixture And Good Engine Condition Would Normally Lead To Light Tan Or Grayish Brown Deposits Upon Buying New Spark Plugs, Make Sure They Are The Right Type For Your Engine Which Are Mostly Multi-Electrode Types Adjusting Gaps Is Unnecessary On Such Plugs But If Single Electrode Plugs Are Used Gap Should Be Set According To Manufacturer's Specs Using Proper Tools Always cross thread by cleaning the threads and surfaces of your plug so that you do not get caught up in this mess later on when installing it back Tighten the plugs to specified torque using a torque wrench and a spark plug socket. Replace ignition coils.