|Last updated:||29th September 2019|
In the Name of Allah, The Most Gracious, The Most Merciful
WaAlaykumSalaam WaRahmatullahi WaBarakatuh
If one cannot find water within a one-mile radius, then tayammum can be made.
Tayammum can be made with whatever is jins-ul-ardh (from the earth); including pure earth, sand, stone, cement, brick, baked earthenware (unglazed pots etc.), clay, walls of stone & bricks and clay, and items that have a thick layer of dust on them.
The following principle should be maintained for what cannot be used to make tayammum - whatever becomes ash or melts through burning or heating, or rots; i.e. wood, metal, glass, food, grass etc.
Thus, as per your question, tayammum cannot be made by touching the back of a car seat, nor the roof or floor of the car, unless these are covered in a thick layer of dust.
And Allah Ta’āla knows best
29 September 2019 / 30 Muharram 1441 AH