By far the easiest-to-follow guide we came across - our own experience says you should set aside maybe half a day to buy the parts and get fully installed.

This is the only guide that assumes absolutely no knowledge of cars. Impressively, our support ticket was responded to in under an hour (although it could take a little longer at weekends), and there is an unconditional 8 week guarantee. Best of all, the technology required is readily available and cheap - we were able to access all the parts needed for well under $50. Given that its proven to increase fuel efficiency by as much as 40%, you could well recoup your investment in under a week.

May 2008 Update : there is now a promotion running on the site, and it is temporarily available for $49 instead of $297 - as such, we recommend ordering sooner rather than later.

List of Features

• Fast and easy setup; works for complete car novices; proven fuel savings of up to 40% - our top pick
• Installation works with any gas or diesel powered car, van, truck or SUV.
• The technology required is readily available and cheap - we were able to access all the parts needed for well under $50.
• This is the only guide that assumes absolutely no knowledge of cars.

Our second pick uses the same technology as our top pick - and again, we were impressed by the fast support, money-back guarantee and low setup costs.

The guide includes two bonuses (how to get the IRS to pay for your upgrade and how to make $300 an hour installing the systems for others, arguably worth the cost of the guide on their own.

All in all, its a great package which means you can be enjoying massive fuel savings for very little, very quickly. So why only four stars? Well, perhaps we were spoiled by our top pick, but we found the directions a little harder to follow - and since ease of use is so important, we decided to knock off a star.