I had to look up NOACK http://en.wikipedia.org/wiki/NOACK_Volatility_Test
it's how much the oil evaporates under heat load.
I've never heard of Pennzoil Ultra. I found their page http://pennzoil.com/motor-oil/pennzo...synthetic-oil/
It looks like the ST takes 5W30 oil
according to the PDF from the pennzoil page the NOACK of their 5W30 oil is 11.9
There are two links on that page to buy the oil. the 0W40 and the Euro formula. The link for the 0W40 shows a single quart bottle and it costs $54.19 I think that can't be for a single quart. I searched google shopping and there was an ebay link selling 5 gallons (20 quarts) for $129. So that works out to $6.50 a quart.
on Amazon they have the 5W30 in a 6Pk (one oil change for us) for 51.95 ($8.66 a quart). They also have the 0W40 at $13.09 a quart.