Hi. I bot this used S40 from the dealer with an extended warranty. 36 days ago I had an oil change at Midas. Throw weeks ago I noticed mild issues with the throttle. It seemed sluggish. Yesterday I noticed really loud knocking, so I took it to the dealer. The service manager listened, and diagnosed the bearings were gone, and checked the oil. It was very low and dirty. Today he had it on the hoist and said there was only 1.5 litres of oil, but that the filter was not collapsed.
So, is it likely that Midas failed to put in any new oil, or did my car go through 4 litres in 36 days? I drove 8,000km in that time.
finally, is this likely covered by warranty?

 

Burning that much oil you would have seen a cloud of blue smoke during acceleration or deceleration. You can check the spark plugs to see if they are oil fouled. This would be covered under warranty.

If it's a leak you should see a puddle under the car and the bottom of the engine would be oil soaked. This would be covered under warranty.

If none of those apply then look to your Midas oil change. This would not be covered by a manufacturers warranty. I'm not a lawyer so don't take my word though.