I own a 2016 WRX that I bought new in March 2016. On suggestion from a few members here, I decided to use Pennzoil Platinum 10W-30. The reasons are as follows:
- Fuel dilution (especially when there are lots of short trips in cold temperatures without longer trips to warm oil to full op temp) causes premature shearing and viscosity loss. The PP 10W-30 variant holds up to this dilution better than the 5W variant due to the fact that it doesn't need as much viscosity modifier, which makes the oil more unstable (more susceptible to vaporization/mass loss at higher temps)
- NOACK. At 4.7%, PP 10W-30, last time it was measured, had one of the best NOACK ratings of ANY oil on the market (I really don't know of an oil with a better rating than this - if someone else does, please chime in
). NOACK is so important on a TGDI engine because of the high temps and specific outputs of these engines and the potential for intake tract deposits. A more stable oil will experience less vaporization under high temps and less intake tract deposits.
I've had 1 UOA with this oil (sample taken when I drained the first PP 10W-30 I'd used, after about 5500 miles):
It held up pretty well, as you can tell. I might get another UPA here when I do my next oil change.
I do always use a premium, Top Tier fuel, and, preferably Shell.