Mahindra is not willing to disclose which oil grade I am supposed to use in my cars, 3 mahindras, I have to top up when I fill my tank with fuel at a service station, mahindra is not willing to disclose if it is normal multi grade, semi synthetic or full

Mahindra is not willing to disclose which oil grade I am supposed to use in my cars, 3 mahindras, I have to top up when I fill my tank with fuel at a service station, mahindra is not willing to disclose if it is normal multi grade, semi synthetic or full synthetic. Why should this be a problem to disclose, if you mix the wrong oils it will damage your motor. I have a kuv100 diesel, tuv300 and a genio bakkie.