Gumout 510023 Regane High Mileage Fuel System Cleaner 6 Pack 510023W-6PK

Went from 15.7 to 17.1 mpg. Only thing i did diff was add this stuff once a month.

Backstory, I should have used fuel system earlier in my car. At about 120k, the engine started knocking, especially with the AC running. I have used predominantly Sam's Club gas, 87 octane. I never used fuel system cleaner until then (I have in my other cars, but just never did in the Prius. With the gas practically empty, I put in a bottle and only put in 4-5 gallons of gas. It definitely helped with the engine knocking. I now use it regularly (everytime the engine starts knocking again every few thousand miles.) I did originally try this on an empty tank and filled it up the tank......did not stop the engine knocking. Thus now I only put in a few gallons. Did it improve mileage....NOPE. I did not see any performance increase.

I use these every around every 5-6 fill ups and use the Gum Out Tune Up in the white every oil change (5k miles). My truck is 25 years old has 125k on these spark plugs. Put it in shop for a tune-up. My mechanic told me the plugs looked brand new and the fuel system was spotless.

Arrived as advertised

Because this is one of the few products that I am aware of that contains PEA's (Polyetheramine) I use this product in all my vehicles every now and then to clean out the injectors and intake valves to prevent carbon build up.