Mostly hacks are described here, on the forum.
You can find function for fuel consumption hack by @AngelWolf, I believe it is at page 73.
What I did - I just searched values in double (grams for weight and millilitres for fuel), changed them as it is. And, well, you know the result. You can keep playing with this, but no online options available for you anymore.
For perk values hack I use 25% perks, which are mostly battle perks. Just search 0.25 Double. Other perk values may be harder to mess with since some data crashes game when being changed, and you have to change a lot of values to find correct ones.