I think my 2012 Hyundai Accent owners manual recommends a bottle of their Techron equivalent every 15,000 mi. if "top tier fuel is not available." I've been adding my own Techron to the gas when I fill up at a non Top Tier gas station. I've been adding 1 oz per 10 gallons of gas (with the old formula.) The newer more concentrated Techron would need a little less I guess.
But here's some valuable info:
The car has never seen anything but Top Tier gas or if I get a really good price on non top tier, I add a little Techron to cook up my own "top tier."
I've noticed the car will ping now that the summer heat is in full swing. It pings at low RPM when climbing steep hills in the hot weather. I'm assuming its because of combustion chamber deposits conspiring with the 11:1 compression ratio causing this. So, I guess the top tier and/or my "top tier" concoctions are not working to keep things clean! I run the 87 octane that the owner's manual says the car will run on just fine.
The car did not ping at all when it was new last summer under any conditions.
By the way, it is the "Gamma" engine. 1.6L with Direct Injection. It DOES NOT get the "exceptional" gas mileage like people have been led to believe (me included.) But you would expect it to since it has 11:1 compression, VVT, Variable length intake runners, direct injection, a 6 speed auto that runs low RPM at high speeds, and one of the lightest overall weights of any car on the road. To get the 40 mpg claimed highway rating you have to drive under absolutely ideal conditions.
Any comments appreciated.