I bought a 2nd hand 2015 Mitsubishi ASX VRX 4mths ago. I am the second owner, the previous owner was a council. It has high kms for it's age (now 187,000km) however it has been serviced by Mitsubishi at 15k, 30k, 45k, 60k, 75k etc and has 11 services in total. Due to lockdown restrictions I drove it maybe 6 times in 2mths, since restrictions were lifted I have done about 1800km mostly around town. About 1mth ago I did a return highway trip of approx 300km. The next day I noticed a 15cm spot of oil on the driveway although as my husband had brought home his 26yr old work truck I thought it was the culprit. Fast forward 1 month and I did the same highway 300km round trip and there was oil in the driveway again. I got under the car the there is a large stain of approx 40cm on the floor pan and obvious drip. The stain is located at the rear of the engine and only slighlty to the passengers side. I waited until the next morning and checked the oil levels and it is full. There are no warning lights that are permanently on on the dash. It doesn't leak oil on the driveway or where I park when using around town, only after a long trip. Although I suspect this may be due to much longer running times and overall temperature reached on long trips. I checked the VIN on the NZ Mitsubishi website and it was not subject to recall. Now that I have an issue I have been doing more research and found an article from drive.com.au that describes the particulate filter needing to regenerate itself from time to time and, if the car hasn’t been driven over a distance at highway speeds for a while (I wish they defined "a distance and a while"), the ASX can take things into its own hands. As part of that process, the computer instructs the fuel system to inject more fuel into the cylinders to try to get the exhaust up to the temperature required to regenerate the filter. The problem – and it’s by no means restricted to Mitsubishi – is that some of that excess fuel finds its way past the piston rings and into the sump where it dilutes the engine oil. Eventually, the oil can become so degraded that it’s incapable of lubricating the engine, at which point terminal damage occurs. So my first questions are:

Can anyone advise as to what could be causing my "long distance" oil leak?
Should I have a warning light permanently lit up on my dash?
If it is terminal damage as described by drive.com.au would signs of this show when servicing the vehicle?

The other thing I have noticed is that there are 2 warning lights on the dash that are slower to turn off. For now they are turning off but they are always last to go out.

Is a light that is slow to turn off indicative of a looming problem?