Use and utilise mean the same thing, right? Well, not exactly. As well as spurning one of the tenets of Plain English, using utilise risks interpretations you may not intend. Although we find that misused words tend to embrace their corrupted meanings over time, this particular difference is still worth pointing out. I like the nuance that a correctly employed 'utilise' can bring to writing.
How to use utilise
Utilise may appear legitimately in scientific writing, e.g. 'vitamin C helps your body utilise the iron present in your diet'. In this context it means to make practical or effective use of something. In a financial context the word means to turn to profitable account, e.g. 'excess stock was utilised to fulfill charity obligations'.
How not to use utilise
Somewhere along the way someone decided to swap use for utilise as a way of sounding like they were super awesome at words in general business writing (much like the misuse of myself). However, there are subtle differences in meaning, as you might have picked up from the examples of utilise used correctly above.
While 'use' denotes the employment of an object for a purpose, 'utilise' denotes the employment of an object for a purpose for which it was not intended. To demonstrate: in sentence A, Karen is using the phone book for its intended purpose. In sentence B, Karen is using the phone book for a purpose it was not originally intended — she is making practical use of the phone book.
A: Karen used the phone book to look up the number.
B: Karen utilised the phone books to make a garden bed.
In summary, unless you are writing a scientific article, or are explaining an innovative business venture that creates something unexpected using existing tools/technology, stick with use.