The only illuminated "replace engine immediately" warnings I have ever seen were from engine fires. Even those weren't full replace engine faults, but they did kind of blister the paint pretty badly (and the Crevette needed a whole new bonnet).
On my ford transit there was a sensor on the exhaust return that would light up during long motorway journeys, after several 400.- invoices for "fixing" this I asked what they were doing ... " Oh nothing" said the mech "it just gets stuck for a second or 2 and triggers the warning light ( which stays on ) we just reset it ( the system) so the light goes out" !!
400 francs !!!
To switch a light off..
I drove the following 200'000km with the light on ...
As big blue says, don't panic it's not really broken ( unlike my land rover 2.5TD with a hole in the piston.. that was really proper broken )
I would love to see a photo of the place engine warning though ..
As stated the nozzles are different -petrol is smaller and green, diesel is bigger and black. In the US it's the opposite - diesel is green and petrol is black. Having been used to this, I pulled up to a migros tankstelle here, grabbed the green handle, and started to fill up my diesel. Until i looked down and noticed the 'bleifrei 95' sticker...
total cost of about chf 500.- to drain the tank (it has a antitheft device so it had to go to an authorized garage, or i'd have done it myself). Also, be wary of TCS. The TCS guy came to tow it to the garage, and I clearly explained not to turn the key at all, as that would activate the in-tank pump and contaminate my brand new fuel filter. He said he understood. 5 seconds later he got in and turned the key, and my wallet was an additional chf 100 lighter...
In my case, TCS came with their little car, we attached a tow rope to my huge van, and he towed me a 1/2 km to the garage that way (with me sitting inside steering the van). So using the key was necessary.
In many cases, if an actual tow truck comes and pulls the front axle or whole vehicle onto the bed with a winch, the key might not be needed.
The next day I got a call from the garage asking why I had turned the key, because they now needed to change the fuel filter also. I explained that TCS had done it contrary to my instructions - and the mechanic wasn't surprised.
How cruel, maybe the OP is stranded in the middle of nowhere with his car broken, no LTE or 3G connection*, having nothing else to stare at than the "Broken Engine, abandon ship immediately" message, and cold eyes full of tears.
In case you are still looking for advice, op, it could be that you need your diesel particulate filter (DPF) changing/sorting out. The warning light might lead you to believe (from its appearance: a little engine, yes?) that the engine needs replacing but it is just telling you to get it to a garage. From what you describe your vehicle has gone into limp mode. If it is the DPF it may be that the garage can do a forced regeneration quite cheaply but if it is too full it could cost over chf1000......be interested to find out what the problem was....