Sky, since your vehicle is a late model built to tighter specifications I would go with the lightest weight that still gives decent oil pressure at operating temperature during idle. The lighter oil will flow quicker and, therefore, give faster protection during cold start up. As the bearing surfaces wear with mileage and you experience some loss of pressure with the passing years at operating temperatures you can then go to a thicker weight. I am not a mechanic and I did not even spend last night in a Holiday Inn Express but I have had good experience with engines of all types in all sorts of vehicles through the years. :) (oh yeah, I have read enough articles pertaining to lubrication of my boats, airplanes and sports cars to get atleast an associate's degree).

Viscositeum Est...
 

Whether you use synthetic or Dino, viscosity is the same relative measurement, or at least should be.

Lower numbers in multigrade oils traditionally have meant that they will flow easier at lower temperatures, so people usually will prefer a 10-30 in winter, and a 15-50 in summer, but it depends upon where you operate. 0W40 is reserved in most cases for sub-zero extreme operation, but the North American rep for Lubro-Moly, who lives in San Diego, prefers to use their 0W40 synthetic in his Suburban year-round.

Here's a little lesson on the principles of single weight viscosity for those who may be interested:

www.soest.hawaii.edu/SPACEGRANT/class_acts/ViscosityTe.html

Use what your owner's manual specifically recommends for your climate conditions in Vancouver...

Oh yeah, one more thing......
 

The viscosity will also affect how quickly the hydraulic lifters can bleed off pressure. Some vehicles will experience 'pumped-up' lifters if the viscosity is too heavy and RPM's are high. This, of course, can lead to poor performance and burned valves and, in extreme cases, possible interference with piston travel.

Re: Oh yeah, one more thing......
 

So higher viscosity will create poor performance and cause the car to burn valves???

The Bottom Line...
 

Sky, years ago Ford had a technical bulletin out on the four cylinder engine as in my Ranger. It seems that heavy weight oil would not, indeed, let the lifters bleed down quickly enough. Of course, if the valve does not make contact with the seat it is unable to dissipate combustion heat and, yes, therefore may lead to burned valves.

As Longston said, use what your manual calls for. My VW owner's manual says to use 5W-40, but 5W-30 can be used if 5W-40 is not available. So "40" is the perferred weight. My '80 SD's manual says to use 15W-40 for temps above 23 F. Below that, use 10W-40 or 50. Again at least "40". Domestic and Japanese cars call for anything-30. It seems everything from Europe calls for the heavy oil. Look what Porsche is factory filling their cars with, 0W-40 Mobil 1. There's that number again, 40.

I was talking with the vibration guru (Doug) from work during lunch today and asked him what kind of oil he uses at home and the change frequency. He stated that he uses Mobil 1 in both his vehicles (Hondas - one with a six and one with a four cyl) and his change frequency for the oil and filters is the same as the Mobil Lubrication engineer that he deals with - twice a year - once in the spring and once in the fall. I was pretty surprised because in the lubrication engineers case you are talking over 15k miles between oil changes. Doug went on to say that the last car the Mobil guy had the engine lasted for over 300k miles with the majority of these being highway miles. If anyone is interested in discussing this with the Mobil lubrication engineer I can send his email address upon request. I change my oil more frequently than twice a year but then again I do not use synthethic oil.