I run a pennzoil FI/Carb cleaner every two tanks of fuel. I wait til I have no more than 1/4 tank of gas left before I add it as the bottle states it can only treat up to 80L. Who knows for sure tho, so I make sure I have no more than 35L left before I add it. I ran it in my 2.5L dodge before it retired with over 280K. If the frame was still in good shape I would've replaced the brake lines, but I sold it off instead. Engine was still in great shape - changed the oil every 2500miles! That car saw 14 winters. Two of which were in a constant -40C where if you didn't use the block heater - you weren't going no where.