I use this website for many calculations... whether it's cooking conversions of tablespoons to teaspoons or AUTOMOTIVE STUFF
http://www.webcalc.net/menu.php
SCROLL TO THE BOTTOM OF THE LIST for the
AUTOMOTIVE section... or just clink this link...
http://www.webcalc.net/automotive.php
There's just about every kind of automotive calculation here that you can think of.
Just figured I'd post it for your pleasure...