I let the red color start at the same value, I think it was 110, can I compare it in that case? Also, the graph shouldn’t be changed by the color scale right? So the graph should be correct?
Yes the graph is definitely independent from the range of the bar 
So the new car is in fact less aerodynamic than the old one?
If it produces more drag, it definitely has larger resistance. A good way to compare the aerodynamic performance is the L/D ratio (Lift/Drag) though.
Does a higher ratio mean better or worse?
Hey, you need high Lift and small Drag, so a higher L/D then
Oh that’s a relief 
The L/D for the new Car is higher, so it’s better than the old one. Also, why is Lift good for the car, is it because it lifts it up from the ground and it has less friction or something?
Ah let me rephrase it, for devices like aircrafts, it is good to have a big positive lift value, but for cars, it is good to have a big negative lift value which counts as downforce. If you have a vertical force of -100 N, it means you have 100 N of downforce.
So if you are comparing the aerodynamic performance of vehicles, the ‘L’ should stand for the downforce produced. The bigger the downforce, the greater the aerodynamic performance.
This forum post contains too many different topics, If you have a specific question, feel free to create a separate one.
Cheers!
Oh but if I need a big negative lift, is a high L/D Ration equivalent to better aerodynamic performance still?
" but for cars, it is good to have a big negative lift value"
“The bigger the downforce, the greater the aerodynamic performance.”
Aren’t those to opposite statements? Like in the top one you’re saying the lift has to be low and in the bottom one you’re sayig that it has to be high, what am I missing
Downforce is a downwards lift force as explained here
So these statements are not opposite, you need a lot of downforce, which is negative lift.
Ohhh got it, but I is a high L/D ration still good, or is it bad in terms of aerodynamic performance?