Originally Posted by Staples

Not necessarily true, unfortunately. Not all gas is created equal and there is such thing as bad batches, especially when it sits for a while in the underground tanks and creates moisture. I try to use the same gas continually from where my car was tuned on. I still had an issue where there was water in the tank which drops the octane levels and can cause detonation, not the tune's fault in the least. I had to drain the bad gas, fill up somewhere else and did some data logs. After a few pulls, I made all the timing back and the air fuels were dead nuts as they were on the Dyno originally.

It's always a good idea to choose the gas stations that have the most amount of traffic and half a quart of Torco Accelerator has worked great for me on every fill up.