you can effectively turn any gas into "top tier" by adding detergent on your own. I add in some Redline approx 500 miles before every oil change.
Techron works fine, too. I used to put it in my Gen 2 every few fillups. Posted via the PriusChat mobile app.
I am so glad to hear that the CT is doing so well as a high mileage vehicle. I just bought my wife a nice little CT with just under 100K on the clock. She is lovin' the upgrade from her 3rd Gen Prius.
I was considering a CT as well...also great as a 'stealth hybrid'. Prices seem to be coming down nicely but there still is that 'Lexus premium'.
I'll be going back to Klean Strip paint thinner once I use up my Techron supply. It has the same compound that Gumout and other injector cleaners contain, and all those cleaners use petroleum distillates as a general solvent and carrier for the more active ingredients. The paint thinner I had before wasn't the low or no odor type, and I'll try to get in again on the believe the lighter fraction provides a wider range of cleaners to the mix. Some 91% isopropyl alcohol thrown in won't hurt. I'm thinking of trying some straight biodiesel as an additive. It keeps diesel systems clean. Acetone is also an effective cleaner. Much of the acetone improving fuel economy proof is likely due to it cleaning out a gunky system. It just can damage the car's paint if it gets on it.
Note that the active ingredient in Techron is "polyether amine (PEA)". This is the ingredient you want to look for in any of these cleaning additives. Most lower-priced additives do not have it.
Well, I haven't notice any difference between using the Techron and the paint thinner. Though I have heard the Techron is better for cleaning out a neglected engine. Then again, the ethanol many of us are forced to use is also an effective fuel system cleaner. In older cars that have run just straight gas their entire life, it can cause the same problems as biodiesel in older diesels. It loosens up the built up gunk that can clog things up.
345k is pretty good. I just read about your head gasket issue. I'll post this anyway. If your main seal is leaking, high mileage motor oil like valvoline max life have seal conditioners in them to prevent seals (main/valve/pulley seals) from leaking. I have personally used the atp reseal to stop my main seal leak on my ridgeline and has not leaked in 65k. It saved me 1500$ as well.