My 2020 LDV T60 surging

It would appear the vehicle has gone into limp-home mode. This limits how much power the engine produces and how fast the vehicle will go as a means of protecting the engine and transmission from damage due to whatever the root cause is. Often a low coolant or oil level or high temperature will force the car into limp-home mode, but there are many other reasons for this to happen. You need to take the car to a workshop which will be able to scan the vehicle electronically and gain a better idea of what’s going on.

Don’t forget, either, that provided you car is less than five years old and has travelled less than 130,000km, it should still be covered by the LDV factory warranty.

As for the colour of the oil, diesel engines are notoriously filthy things and nearly always turn their oil black in a very short space of time. In fact, even when topping up with new oil, by the time it has reached the sump and appears on the dipstick, it’s already black.