Is it permissible to sell petrol to friends to recover 1000 euros, after the company retracted a better job offer that included providing a car and a petrol card for the employee?

The second company did not change the previous offer entirely, but only for two months, after which they will deal with you according to the presented agreement. Their verbal offer might be general, and your judgment about the flimsiness of its reasoning is not necessarily correct, as many companies differentiate between benefits for an initial period and those thereafter. The right you are claiming is not certain, especially with the manager's denial, and this issue is not among the situations where rights are permitted to be exacted upon their attainment. Therefore, you are not allowed to sell the fuel allocated to you.