I almost got the oil from Wal-Mart ($37 for 6 quarts) but it turns out to be a slightly better deal to just get it from the garage because they charge a flat $20 extra (the Si needs about 4.5 quarts.) I also decided to replace the transmission fluid with the new Honda one that just came out (p/n 08798-9031) and the guy was nice enough to do it for free.

Overall I was happy with the Mobil 1 Lube Express and I will be going back. The tech was really friendly, the whole thing took less than 30 minutes and I really liked how I could stand in the garage and watch him work. They also have these $10 off coupons on the web so with full synthetic it came out to $44. Considering I paid $32 at the dealership for the last one this is a much better deal. Some remarks:

ALWAYS make sure you check your oil level before you leave the shop! The mechanic consulted his computer system and said my car needed 4.2 quarts of oil even though I repeatedly told him my manual says 4.6. At the end when he checked the dipstick it was on the low mark and only because I was hovering over his shoulder did he top it off with another third of a quart. I suspect the numbers they use are purposely on the low side to save them money because most people will never notice. Especially since the same thing happened after my first oil change at the stealership, except that time I didn't check the oil level until the next day and had to top it off myself.

I forgot to ask so I got stuck with a cheap oil filter! For an extra $5 they can use a Mobil 1 but you have to ask for one. Next time I'm going to either buy a HAMP filter online and bring it in or just get a Mobil 1. I think I remember reading the Mobil 1 was one of the better filters available.

The new transmission fluid is silky smooth! Third still has a little bit of notchiness sometimes but it definitely feels better and is well worth the $12.

My first tank after this oil change was my best ever! I averaged 27.8 mpg over 335 miles, including about 75% highway and 25% city driving. Of course part of it was due to the fresh oil but considering my previous best was 26.6 mpg the synthetic oil must be partially responsible. So while the oil changes are going to cost more, it's looking like I'll definitely be saving on fuel.