But what exactly do those codes mean, and, in particular, what does the "W" stand for in engine oil? When it comes to understanding these codes, the "W" part is perhaps the easiest to remember.

A step-by-step guide to help you fill out a W-4 Thanasis / Getty Images You're about to begin that much-needed, new job and your employer hands you an IRS Form W-4 to fill out and submit to them ...