No it isn't. What you need to do is use natural language instead of trying to force feed keywords to the SE spiders.
When a page is about cars, you should use words that are related to cars instead of repeating the word "cars" hundreds of times. How would a group of real car lovers talk if they were standing around at a party? They would be talking about all sorts of features that are related to the cars that they have or lust after.
Your best bet is to get a really good writer that understands NOTHING about SEO.
