Yes it is, which means that if you don’t do regular runs at highway speeds, the filter is prone to clogging up and requiring either cleaning out or even replacement. The filters for this car are advertised for anything from $200 to $800 for a second-hand DPF, but you could be buying one that is well past its best.

In a more general sense, any second-hand Epica would need to be super cheap before you’d consider it, as they were a slow seller and not a particularly good quality car even when brand new. Unloved then, they’re unwanted now. There are definitely better choices.

Seems like you might have two problems here. The first is that I suspect you’ve may have fried the computer in the Holden in the process of jump-starting your other car. Jump-starting a modern car with on-board computers is something that should only be attempted by somebody who is a specialist. There’s a specific technique that goes beyond simply hooking up the jump-cables and hoping for the best. It’s all too easy to send a voltage spike through the car and send the computers into melt-down. That would explain why the car will not restart.

As for the milky oil and the sludge under the oil-filler capo, that sounds unrelated but still serious. A blown head gasket can lead to this exact set of symptoms and it occurs when the engine’s coolant is allowed to mix with the oil (and vice-versa). Sometimes in these colder months (particularly in Tassie) it’s not uncommon to get a small amount of frothy, grey muck under the oil-filler cap, but not a huge amount. And if the oil on the dispstick is also covered in oil contaminated with coolant, then you’re looking at a new head gasket at a minimum.

I’m not sure I agree that all modern Holdens were problematic, but the Epica, which was really a Daewoo (it was built in South Korea) with Holden badges, is definitely on the suspect-reliability list.

As it is an intermittent problem it’s hard to be definitive, but I would suggest you look at the fuel system, and check for a faulty electrical connection that could affect the operation of the fuel pump or injectors.