Australian-born MacKenzie - who took up the post earlier this week - replaces Greg Fountain, who has left to pursue other interests after three years in the job.
MacKenzie is to seek to broaden the readership at a time when mainstream motoring magazines are under pressure.
MacKenzie said: 'All good magazines need to re-invent themselves continually. Car has been around for 40 years. We need to communicate the core values such as passion, insight and irreverence more clearly to existing readers, and to offer an easier entry to new readers wanting entertainment and escapism.'
MacKenzie said he would be introducing a number of changes to the structure and lay-out of the magazine.
'I want the structure to be simpler and more accessible, and we are looking at the design to give the pages a less intimidating feel. The content will stay the same, but we want to make sure we have the best use of context - the "why behind the what". It is a general freshening up,' he added.
Emap Automotive creative director Duncan Edwards said: 'The magazine is seen as being too industry-focused, quite a serious read - we want to make it more entertaining and fun to read. Perhaps the best analogy for what we want to do is what the BBC has done with Radio 2.'
Edwards said that the proliferation of car-related media - from manufacturers' websites to Sunday paper sections - was putting pressure on the mainstream car magazine market, but that MacKenzie was well-qualified to meet the challenge.
MacKenzie joined from the same publisher's Automotive Management magazine, which, as editor, he re-launched last year.
'He has a lot of magazine experience, good judgment and loves cars. He also has just the sort of knowledge, insight and anecdotes that readers would die for,' Edwards said.