Hi Willy,
These days I nearly always shoot in manual,metering off grass or tarmac,or track,whichever is closest to what I want,adjusting on ISO to conditions.
However,shutter speed may be better for you,depending what blur you want on wheels ,which could be anything from 60th to 500th,depending on speed of panning ,and speed of cars !
Many better photographers than me on here will have better advice.
Most motorsport seems better below 250th if you can use it,though keeper rate falls with shutter speed.
There is a fine line to tread for the ultimate shot,or an easy line for safety and parked cars.
2.8 to f4 lenses do help,big time when light is poor,as do the very best cameras.
Really good technique has to be taught and learned(I am still on L plates),and it's an expensive game this motorsports photography ,as we all know.
Regards,
Pons