My :tc1:
When I picked up my '07, the dealer had filled it, but with 87 octane. I did notice some pinging, but didn't realize until later that they had put in 87 octane. On my first fill-up, I put in 92 (my choices here are 87, 89, 92, 94, or racing fuel), and noticed an improvement in performance.
For the following fill-up, I put in 87 again, recorded the mileage on the highway, did it again with 92, and noticed 3 to 4 mpg improvement with the 92 octane fuel. Here in Northern Ohio, there is a $.10 difference in the price between regular & mid-grade, and another $.10 between mid-grade and premium. Let's not talk about the price of the racing fuel, which is unnecessary in the ST
.
IF my ST was completely empty, you're talking a increase of $1.54 between regular and premium for a tank of fuel. I'm guessing my annual mileage between 8k and 10k per year, so for me, it's a no-brainer (which I've been accused of
). I'll use the 92. I haven't spent the time to do the math, but I'm ok with the difference in the price. Remember,
YMMV!!