And which ones were on top?

I knew someone was going to ask that. Unfortunately I did not commit the (lengthy) list to memory. My short list consists of Mobil and Amoco (which became BP Amoco) so they were right at the top.

I get a knocking or pinging consistently when I am going up hills and occassionally on flats between 5 and 15 miles per hour. If I accelarete strongly the car moves fine and the pinging stops, but it will return if I going to normal acceleration. I use regular unleaded, usually Chevron or some other reasonable brand.

Based on previous posts, it sounds like this is Probably worth taking to the dealer?

I have also had pinging frequently. Using Shell and Esso in Canada. I tried Husky and it seemed to occur less frequently. I would be interested to find what somebody hears from the dealer. I will bring it up on my next oil change visit in 2 days.
It is hard to hear it when the windows are closed.

A piezoelectric element in the knock sensor will sense the pinging or knocking. It will then in turn retard that particular spark coil and cylinder or cylinders to help keep it from knocking. I don't know yet if this 2.4 engine has two or four knock sensors.

I experimented with gasoline with my broke-in '03 Corolla using the scan gauge. The Corolla has a 1.8 liter engine. I ran the tank down and then bought some cheap (save-a-lot) 87 octane gas and noticed that the engine did not start or accelerate very well. Gas mileage fell about 3 gallons per tank.

I set the scan gauge to view the ignition readout. This allowed me to see the overall advance. I had a particular mile of highway with a slight upgrade so as to compare. I did remember using Chevron back then that the ignition was usually rather high advanced.

I noticed with the cheap gas (saved a dime a gallon) that the overall ignition would retard down to 17 to 21 degrees. After a few tanks of good gas I noticed that same stretch of highway the ignition would stay up to 35 to 37 degrees. From my early days of messing with gas mileage. I do know the higher the ignition the better the mpg. I do know even with good gas, its going to retard normally for lower rpm and when power is needed.

Like someone here says, be sure to use quality top-tier gas from the top tier Retailers list. I have seen some gas that can dirty up your injectors and valves. Don't use the mom and pop refinery-gas in your $25K new car. If its not on the toptiergas.com/ list, then don't buy it.

If you engine pings you might try about 4 ounces of Lucas injector cleaner or gas modifier when you fill your tank. Their may be some other good brands. I have had good luck with this one when needed. I used it on my wifes pre-owned '91 Ranger pickup. No telling what gas the original owner used. At 20,000 miles Ford said, she needed new injectors for about $250 and a $45 fuel filter plus labor. Four tanks of quality gas including the Lucas treatment cleaned them up. She routinely adds a few ounces of lucas at ever fill up. Hers is a flex fuel engine and I read the Ranger pickups have tendency to knock under a strain.

I can't find that CR article on gas comparisons. I looked in the 2007 CR Buying Guide. I do seem to remember that article. That may have been a 2004 or 2005 issue. Shell may have been a poor gas back then. Remember when shell started all the TV ads telling how great there new gas was, higher mileage and a clean engine. That must have been their move to get on the top-tier gas list. Here in south I remember most of the Texaco stations being changed over to Shell.

Another low priced economy gas was Phillips 66. A few years ago they did a complete turn around. They added the extra additives to bring their gas up to top-tier quality. I have used it for a few years now, once they started stating there gas that can clean your engine's injectors and valves. My '03 Corolla averaged 40.5 combined mpg. Straight highway at 60 miles per hour with air conditioner my best was 45 mpg using phillips 86 octane. It's 4400 foot elevation here in the high desert.
I live 85 miles north of El Paso,Texas. Here in this town there are 5 new phillips 66 stations. Five new Conoco stations have been added this last year. Some of those were Exxon stations that are now Conoco.. My TCH came with a tank of Conoco in it and it ran fine. I have not talked to the Phillips tank truck driver as yet.

I would like to try Shell but their driveway here in town is not very level.

I don't understand why Exxon don't join the top-tier list.

Yes, our '93 Toyota pickup will ping like mad in the summer on anything less than premium. We, the dealer, and a top-rated independent Toyota shop tried everything in the world, but it just likes the expensive stuff.

It's still running great at 140,000 miles (we don't drive it much anymore), though, so whatever's "off" about it isn't fatal.