I've been driving the Focus lately, and since the change over to winter blend I've noticed lack of power and some detonation. Not a whole lot of detonation, but it's evident at low RPMs. For giggles, I asked the wife if she has been experiencing anything.

"Oh, so that's why my truck sounds like a diesel!" She said, after I explained what detonation is. Great.

Now I know the plural of anecdote isn't data, but we fill up from separate stations. I fill at a Valero and she either hits the nearest Shell or Sam's Club. We both noticed detonation, rather noticeable at low RPMs, since the switch over. I've now run 1.5 tanks of mid grade through the Focus, and have noticed less detonation. No new data on the pickup yet (as she barely drives it). Has anyone else experienced any issues with winter blend gas this year?