look up any word, like fellated:
 
2.
to stick ones thumbn in another persons ass hwhile they aren't expecting it. this is commonly known as checking the oil!
once on has checked the oil it is prpoper to charge them fo rthe service with the credit card.
hey man why did you just stick your thumb up my pooper?
"yeah your oil is a little low "
by the guy rules April 21, 2005
 
1.
before a male has any physical penal or oral contact with "strange" vagina, he must first "check the oil". a simple dip of the finger with a discreet sniff, sniff will do. if the oil needs changing the test finger should be jammed into the female's nostril. if not, have at it, til its done swoll.
yo gashmaster, what's that gnarly patch on your upper lip? didn't you check the oil before lickin the wound?

after checkin the oil, i told her to turn around for some puppy.

by buzz August 18, 2003
 
3.
When preforming the sexual act of "the shocker", after you insert the "stink finger" you lick it off, as to "check the oil"
Man, she was so gross but I checked her oil anyways
by Billy Leblanc April 24, 2004
 
4.
before a female has any physical contact with "strange" wang, she must first "check the oil". a simple dip of the finger with a discreet sniff will do. if the oil needs changing the test finger should be jammed into the male's ass. if not, have at it, til you're satisfied.
by pun tang October 17, 2003