understanding latent symantic indexing is required for on page otpimistion.
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.