[Mondaveo]

Hey lexst, welcome to the forums.

Well it certainly sounds like you're going through some tribulations over the past couple of years. Unfortunately, I can't offer any suggestions for repairers up in Queensland. I can only comment from afar on what I read. I'll offer my take (for what it's worth) and maybe it will help us all pick apart what's going on.

First up the "Change Oil" message is likely appearing because the service reminder wasn't reset at the last service. It's just a time-based reminder that starts showing after 12 months have elapsed from the last reset, sometimes the shop forgets to do it. You can easily reset it at home to test this (turn car on but don't start engine, press and hold accelerator and brake pedals together, OK at the prompt).

The report from the exhaust shop is certainly confronting reading. I would be wanting to know how things got into a state like that. Why was the engine oil degraded? How did the turbo and DPF get contaminated with oil? It seems like they threw new parts at the car but you still left without it 100% resolved?

I trust they checked the fifth injector (fuel injector at the DPF) when they did this work. We have seen that injector can get caked with carbon deposits over time and cause regenerations to fail, which you'd see as something like the intermittent 'Engine Malfunction' warning you've been seeing.

In the case where you're chasing an intermittent issue, I suggest you get an OBDII scan tool so you can probe for Diagnostic Trouble Codes (DTCs) and monitor for yourself. Our Mondies are actually pretty poor at communicating when there's an issue, because less severe DTCs (which you'd still like to know about) usually get erased when the engine is switched off. This means you might see a message or experience a breakdown, but by the time a technician looks at it there's often no record in the car's computer. The exhaust shop's report lists a few DTCs they found, but it's perhaps not enough to tell a full story.

I have an OBDLink MX Bluetooth dongle which I keep plugged into my car, paired with the FORScan mobile app on my smartphone. This setup can interrogate both standard HS-CAN and Ford proprietary MS-CAN interfaces. The nifty thing about the the OBDLink is it has a power saving feature, so I can leave it plugged in all the time (won't drain the battery), and it's available any time if I encounter a cryptic warning message or want to monitor parameters while driving around. I had an epic thread on here when I was chasing a transmission malfunction in 2016 and it was invaluable for actually seeing and getting to the bottom of what was happening.

It seems like you could have an issue with failing DPF regenerations based on some things in the exhaust shop report, but the work they did should have resolved things, and there's nothing that clearly points to what the ongoing problem is. So my suggestion, get yourself a scantool and see if you can discover any more details the next time one of these messages appears as it happens. It may also help you clue in on the parking sensor issue.

Keep us posted!