1 Under detailed information you can see a tab dedicated to fuel economy. The fueleconomy is calculated a different speeds at the higher gear possible, like cruising. Depending on the rpm you're cruising the game calculates the fuel required during certain distance. Then (I guess) the value showed is the average of the cruising consumptions.
The size of the fuel tank AFAIK is not calculated.
2 That has been asked before in suggestions, and you can't really know how big the engine can be, because it depends on the configuration, the position and the drivetrain. There are some car bodies where you can fit a front in-line 6 in a RWD configuration, but not v6 in AWD, despite the v6 being smaller.
3 there are 2 steering graphs, the higher speed (under the aero tab) and a lower speed cornering under the suspension tab. You want your steering to be between the red and the blue line. If iit's above the red line it is oversteering. The Y axis is the speed, generally you want your car to not-oversteer and to go as far as you can in the Y axis. IIRC there is a post about that in the general thread. It'scalled suspensioncrash course of something like that. EDIT:
viewtopic.php?f=13&t=3446 This is an old video but it can answer your question
https://www.youtube.com/watch?v=Q7BQf4V ... PH&index=54 Although performance is perfectly
measurable, if you question starts with "
is it better..." there is the chance your get different
opinions on the matter. So, I'll just leave a few links:
https://www.youtube.com/watch?v=UIQjyn9 ... PH&index=1viewtopic.php?f=13&t=10054#p103425EDIT: I add a few links for your questions.