Oil warning light when ignition switched on

[Sallyf]

We are the proud but technically useless owners of a California SE TDI 180A registered in 2012 that has done about 50000 miles. The oil light has started to come on for a moment when I switch on. The dipstick says that we are low on oil. The handbook says that when we add oil we need to buy a different oil if we have DPF. How do we find out whether we have DPF?