So we could have gas to go out in service, of course, Silly!! 
Seriously, (well, sort of - how serious can I be with all these smileys...)
Looking at all the fossil remains with teeth marks actually on the bone or in the shell - the T-Rex tooth marks on various dinosaur skeletons indicate at the least the possibility of predation - personally, I believe T-Rex was a predator/scavenger, taking easy meat when available, and hunting when necessary...: "The teeth of tyrannosaurids are very interesting - rather than being the flat knifelike blades as in most other carnivorous dinosaurs, they are, as Berkeley's Professor Kevin Padian describes them, "like lethal bananas;" more like giant spikes than razor-edged blades. With a mouthful of this murderous fruitlike dentition, tyrannosaurs had a whopping bite, which might have made up for their reduced forelimbs. The bite marks of these teeth are quite recognizable on some dinosaur bones. Some tyrannosaur fossils show evidence of bite marks from other tyrannosaurids, suggesting that there might have been fierce fighting between tyrannosaurs, or even cannibalism....
A current topic in paleontology that has received much popular press is the question of whether T.rex (or other Tyrannosauridae in general) were predators or scavengers. Let's explore this issue.
Paleontologist Jack Horner of the Museum of the Rockies (Bozeman, MT) has proposed that T.rex could not have been a predator. His arguments against predation include its small eyes (needed to see prey), small arms (needed to hold prey), huge legs (meaning slow speed) and that there is no evidence for predation - bones have been found with tyrannosaur teeth embedded in them or scratched by them, but so far no study has shown that tyrannosaurs killed other dinosaurs for food (a bone showing tyrannosaur tooth marks that had healed would be strong evidence for predation).
His evidence supporting scavenging include its large olfactory lobes (part of the brain used for smell), and that its legs were built for walking long distances (the thigh was about the size of the calf, as in humans). Vultures have large olfactory lobes and are good at soaring to cover long distances.
There are arguments against scavenging. Most large living predators (such as lions and hyenas) do scavenge meat happily when it is available, but most do prefer fresh meat. Horner argues that its arms were too weak to grab prey, but sharks, wolves, snakes, lizards and even many birds are successful predators without using their forelimbs (if any). Whether T.rex was a slow animal is tough to tell, as our dinosaur speeds page will tell you...."
From : http://www.ucmp.berkeley.edu/diapsids/saurischia/tyrannosauridae.html
When one looks at the number of predators down thru the eons, one realizes that Earth NEVER experienced a "Garden of Eden" - there were massive, dangerous predators in ALL periods of Life on Earth.
I could go on with various examples; Allosaurus, Carnotaurus, Raptor-type predators, alligators and crocodiles which date back at least 80 to 135 million years (ancient forms, not the modern versions...)
Buuuuut.... When one is talking to literalists who believe the earth itself is only about 49,000 years old - or six human 'days'....
Zid
