SU carburettors on the XJ6,the dashpot oil matters

The twin SU HD8 carburettors on the XJ6 4.2 rely on dashpot oil to control the rate at which the piston rises. Too thin and the mixture goes lean on acceleration. Too thick and it goes rich and bogs down. The correct oil is SU damper oil or 20W-50 engine oil. I see people using ATF or 3-in-1 oil and wondering why the car stumbles. Check the level in both carbs monthly. The oil evaporates over time, especially in the Australian heat. Top up with the dashpot cap removed until it's about 12mm below the top of the dashpot tube.