(third-person singular simple present utilises, present participle utilising, simple past and past participle utilised)
Many style guides have advised against utilize and utilise, arguing that the simpler verb use is always preferable (analogously, that the noun use is preferable to utilization and utilisation). When used simply as a synonym in ordinary writing it can strike readers as pretentious as in “Please utilise the rear door when exiting the aircraft." so should be used sparingly .
Others argue that utilise has other senses, and is acceptable or even necessary (instead of use) in such uses. One such sense is “make best use of" (profitable, practical use, not just general use), as in “if we fail to utilise all resources, we will fail" - here the nuance is not simply “use", but “make best use of". Further, in American usage, utilize can imply use outside an object's intended purpose.