Vauxhall Astra H - 07 1.6 Oil light comes on on long runs - bathtub tom
Back in the '60s, I used to put STP in my old oil burners. Worked miracles.
I do recall an old Hillman Minx with a prodigious appetite for oil for had a miraculous recovery after I started using the 20/50 drained from my other car to top it up.