I recently responded to another post with the following, and it made me think, how much carbon build-up is normal, and when does it become a concern?:
i recently replaced the plugs in my '04 accord ex i4 5-manual with 70,000 miles. i pulled a dtc p0420 and replaced both o2 sensors and so decided to do the plugs as well, even though it was well before the 110,000 mile interval. really, the old plugs looked fine.
with the old plugs removed, i took a flexible flashlight and peered into each cylinder. there was carbon on the tops of all the pistons, but it was thin, and i could see bare metal in a few spots. the engine runs great, and i average 28-31 mpg in mixed 50/50 city/highway driving. my typical commute is between 9 and 14 miles one way, about half of which is on the highway. i have not noticed any performance issues since i've had the car; it runs like it did when it was new.
the valvetrain is pristine from what i can tell through the oil fill hole. for the last 35,000 miles or so i have been doing my own oil changes with Pennzoil Platinum 5w-20 and a pureone filter at 5k oci. before that it was kendall gt-1 synthetic blend with an unknown filter at a service shop at 5k oci.
i have driven the car "softly" from new, meaning i'm not hard on the accelerator and shift generally before 3500rpm. i try to combine trips to minimize cold starts. i also employ some hypermiling techniques like coasting in gear to stops and trying to anticipate red lights. i've used shell 87 only for the last 40,000 miles and before that mobil 87.
i have some gumout regane that i'll run fairly soon but it will mean cutting my oci in half because of it. before that i'll run a few tanks of v-power. when it's all said and done i'll take another peek at the piston heads to see if there was any aPennzoil Platinumreciable change in aPennzoil Platinumearance.
i'm curious if there is a normal range for carbon build-up on the piston heads. i have some on a '93 miata with 107,500 miles. it also runs fine and gets good gas mileage.
i recently replaced the plugs in my '04 accord ex i4 5-manual with 70,000 miles. i pulled a dtc p0420 and replaced both o2 sensors and so decided to do the plugs as well, even though it was well before the 110,000 mile interval. really, the old plugs looked fine.
with the old plugs removed, i took a flexible flashlight and peered into each cylinder. there was carbon on the tops of all the pistons, but it was thin, and i could see bare metal in a few spots. the engine runs great, and i average 28-31 mpg in mixed 50/50 city/highway driving. my typical commute is between 9 and 14 miles one way, about half of which is on the highway. i have not noticed any performance issues since i've had the car; it runs like it did when it was new.
the valvetrain is pristine from what i can tell through the oil fill hole. for the last 35,000 miles or so i have been doing my own oil changes with Pennzoil Platinum 5w-20 and a pureone filter at 5k oci. before that it was kendall gt-1 synthetic blend with an unknown filter at a service shop at 5k oci.
i have driven the car "softly" from new, meaning i'm not hard on the accelerator and shift generally before 3500rpm. i try to combine trips to minimize cold starts. i also employ some hypermiling techniques like coasting in gear to stops and trying to anticipate red lights. i've used shell 87 only for the last 40,000 miles and before that mobil 87.
i have some gumout regane that i'll run fairly soon but it will mean cutting my oci in half because of it. before that i'll run a few tanks of v-power. when it's all said and done i'll take another peek at the piston heads to see if there was any aPennzoil Platinumreciable change in aPennzoil Platinumearance.
i'm curious if there is a normal range for carbon build-up on the piston heads. i have some on a '93 miata with 107,500 miles. it also runs fine and gets good gas mileage.
It might be able to burn the carbon up.. since it's carbon at the "top" of the pistons my guess is just lack of lubrication causing it, since the pistons are doing their job in their regular movements, the oil doesn't really have enough time to "stay" in one place and work the carbon off since you did mention you've "babied" the vehicle.