On a multi-decade long term time scale, oil and gas prices do tend to track in the same directions. I don't think that anyone here disputes that idea. What I and Brad are saying is that on a day-to-day and week-to-week basis, the gas and oil prices are fairly unrelated.
Look at the volatility in the two prices, spot oil vs retail gas. Notice anything different? The gas price is extremely volatile. It spikes and plunges, up and down, over and over again in very short time spans. The oil price is fairly constant. There is very little correlation between these radical moves in gas prices and the more stable moves in oil. A shorter term chart would show this clearly, gas moving up and down without any corresponding swings in oil.
Now look at the scale of the changes. Pick as a starting point, say, the low point around Jan 2007. Oil is $50/barrel, retail gas is maybe $2.25/gallon. Now move on to the peak prices in July '08. Oil is $150/barrel, a full 3 times higher than before. Retail gas is $4/gallon, less than twice as high. If the retail gas price had fully matched the move in oil, gas should have been priced at 3 times it's Jan '07 price, which would have put it somewhere near $6.75 per gallon.