So I'll ask this question, is there really a difference in the octanes you can buy at the gas station and does it really make a big difference in today's engines?
An octane rating measures the fuel’s ability to resist engine knocking, or pinging. The higher the octane, the greater resistance the fuel has to pinging during combustion. The octane rating of gas labeled "premium" or "regular" isn’t the same across the country. One state may require a minimum octane rating of 92 for all premium gasoline, while another may allow 90 octane to be called premium. Some gas stations may offer up to five different octane ratings, including a super premium, which typically has a rating of 93. Other gas stations may call their mid-grade “plus” or “special” and their premium “super.” Valero's premium, in NJ, is 93. As far as what octane's best for your engine, you should consult your owner's manual. My 2009 SRT's 6.1 Hemi has high compression and requires premium. If I filled my tank with 87 or 89 octane gas, the PCM would pull timing to protect the engine and prevent pre-detonation. This would also result in a loss of power and mileage. A 5.7 Hemi, however, can safely use mid-grade 89 octane.
This is good information, it confirms that I'm okay running 89 octane in my 5.7 Hemi R/T. I normally use Shell or BP where I live so I feel better already. I'm surprised that Sunoco isn't listed as a top tier. Around by me a lot of guys that have classic musclecars with higher compression engines run Sunoco because you can select various grades of octane, there's about four, maybe five selections.
