OK not a great day so far, not expecting it to get better but here's my tail of woe.

Nissan Almera Tino 1.8 on a 53 plate has done about 75,000 miles and in the last month it has started chucking a small amount of smoke out the back, whitish grey colour definitely not black.

Had a warning light come on which we got checked and it said the rear Oxygen sensor wasn't working, got this changed car seemed to run better but still some smoke.

Car has always used oil, not loads but enough that we would check it regularly, in the last month this has got worse.

So looks like the smoke coming out the back is the oil burning, hence the oil use.

Nissan dealer looked at it today and says they would need to drop out the engine and take it apart to work out what is wrong as they can't tell where the leak is coming from. They have said it is definitely not the breather pipe. Big scary numbers talked about around engine rebuild if piston rings or pistons are the problem £1,200, but they quoted £500 just to find out what is wrong. Oh and the CAT might well be wrecked as well! None of this works for us as the car is probably only worth £2k and we really want to get rid of it and get something bigger.

Any ideas on any simple (ie cheap) things we should look at that might be worth a punt?

What I have noticed is that the area around the injector on the left of the engine near the oil filler cap is very dirty compared to the other 3, could this be an indication of where the leak is occurring.

Any ideas greatly appreciated, not a bad car when it is running right, just need it to work.