Ping due to ethanol?

I’ve noticed in our two cars recently (coinciding with the new labels on gas pumps showing “up to 10% ethanol”), that when they are warm they occasionally ping at certain acceleration speeds. When I heard this sound on older cars, a higher octane gas would solve the problem. Neither of these cars has ever made the sound before. We always use Sunoco, 87 octane - and pump at the same 2 or 3 stations. Both cars are 4 cyl - one is an 07 Pontiac and the other a 99 Kia. Could the ethanol additive be the culprit? I plan to start using 89 octane to see if it helps.

Ethanol at 10% ought not be a problem. It has been around for many years and nobody has complained about engine knock. (Reduced mpg is another story.) If your gasoline is marked at 87 octane, it should deliver 87 octane regardless of ethanol content. Well, try some 89 octane and then go back to 87 octane. Only you can tell if there’s a difference.

why should the 07 ping doesnt it have a knock sensor?

Knock sensors can only adjust the timing so far. If it’s bad enough, they can’t compensate.

I suppose using 89 octane is worth a shot, but I can’t understand how ethanol could cause this.

I believe that Sunoco also offers 85 octane gas. Are you certain that you have always used 87 octane? You might switch brands for a while to see if that helps, still using 87 octane.

My first thought was to switch brands, using a different 87 octane. But here in the Philadelphia suburbs, there are Sunoco stations everywhere - and we have a card. Just yesterday I pumped 89 for 3/4 tank and am going to keep an eye on it. I’m not sure it’s the ethanol, but both cars have the occasional ping - seeming to coincide with the 10% ethanol labels on the pumps. Or maybe Sunoco has changed something in the mix, but I know nothing about how gasoline is refined & processed.