I work for a university where students are often approved for a Sallie Mae loan, but usually only for a small amount (less than $2,000). When the amount gets higher, then factors like income and the length of your credit history will matter more.
Getting Started. Fouled, damaged, or worn out spark plugs can lead to a variety of engine problems, such as misfires, hard starts, increased emissions, and poor fuel economy. For most vehicles, you should replace your spark plugs every 30,000 miles (consult your owner's manual for your specific interval). It is also recommended that you replace your spark plugs wires at the same time, or you may still experience misfires or other problems.
How often should I replace my spark plugs? A: Unfortunately, there is no single answer to this question. As spark plugs grow older, they lose their sharp edges as material from the center and ground electrodes is slowly eroded away. As the gap between these two points grows, the voltage required to bridge the gap increases proportionately. Even the best ignition systems will be strained to supply enough voltage to completely burn the fuel. It is at this point, when fuel is being left unburned, that the time has come to change spark plugs. Replacing worn out spark plugs with new ones (with sharp new edges) effectively restores the ignition system's efficiency.