This has been a long-standing request. You might want to take a look at some of our past conversations about this topic by searching the forum. Here are a few recent examples: More accurate detail tracking?
, Making Fuelly more "Shoping" friendly
, Drivetrain options and sorting
We know that a certain number of Fuelly members feel exactly the same way you do. They like the site but they want it to do more for car enthusiasts. They want Fuelly to cater to people who know about drivetrains, engine displacement, and a whole host of other options that Fuelly could be tracking. It is definitely one path we could take, but it's not the only path. Our vision for the site involves helping the most number of people possible track their mileage. Through tracking, things can change. So we really feel like getting the most people possible tracking is a good goal.
We also feel like these two paths are separate paths. Making things more detailed for enthusiasts would alienate a certain segment of the population. Asking for engine displacement info up front would tell a certain percentage of people that "this site isn't for me". That's not good or bad, that's just the way it is. But alienating those people is not part of our vision for the site. I think there is absolutely a place on the Web for an extremely detailed fuel economy tracker. It would have an enthusiastic following. But we don't believe that following would be as big as the path we're taking with Fuelly.
I know how frustrating this answer is for car enthusiasts because I've had this conversation time and again here in the forum and in private email. We really do think about this issue quite a bit and wonder if there's a way to make the two paths meet more than they do now. We'll continue to give it thought, and thanks for the suggestion.