Dealers REALLY **** me off when they do this: my dad just bought a 2002 VW Passat V6 4-Motion, and the manual recommends 5W-40 oil. All changes were done at the dealership at their recommended intervals, yet this car burns oil and it's only on it's 3rd scheduled change (it has 12,500 Km). Recently the car burnt 1L in 500 Km, and I found out by turning it on and having the engine shake like crazy and the check engine light flickering. I filled it up with Castrol GTX 5W-30 and took it back to the dealership (the engine ran OK after the top-up), they did some half-assed tests and filled it up with 15W-40 dino oil!! Instead of fixing the issue they put in this heavy oil and expect us to run it through winter (I live in Toronto, Canada and it gets pretty cold in winter)! To make matters worse, this is the 2nd car my dad bought from this dealership, the 1st being a 2000 Jetta with a 2.0L 4-cyl engine. This engine burns oil like crazy as well, and the dealership recommends 15W-40 dino oil all year round as well! We don't really care about this car as it's leased, and we'll give it back in May 2003. After the Passat's oil burning will be fixed (as my dad will have a word with the dealership's owner when he gets back from vacation), what oil would you guys recommend? Should I use Mobil Delvac 1 5W-40 diesel oil, or would the Amsoil 10W-40 be OK all year round?