[06silvy]

Leaks oil (i believe) from the exhaust, engine shakes and has a knocking sound?

 

[SABL]

A "knocking" noise coming from an engine is not a good sign.

Let's get down to some basic questions:

How many miles on the vehicle??

How well maintained is this vehicle?? (oil and filter changes, checking fluid levels, tune-ups)

How much oil is being lost....any puddles of oil under the engine??

How severe is the knock and engine shake??

Any smoke coming out of the exhaust?? (if so, what color)