Some fifteen years ago, when we had a Maruti 800, I could understand the
workshop's maintenance procedures. "Change the oil filter" or "clean the
spark plugs" were things I could relate to somehow, even if I couldn't
do them myself. But things are different now. (Back then, the toolkit
that came with the car had actual tools in it. An combination
jack handle and screwdriver is all you can expect these days.)
About ten years ago, when our car (by then a Maruti Zen) crossed the
40,000km mark, I took it to the workshop (every 5000km for the first
20,000km; every 10,000km thereafter). In addition to various familiar
procedures—brake oil change, coolant change—the service advisor told
me that it was very important to "decarbonise" and "flush" the engine.
Imagine my surprise when I learned that this would add two thousand
rupees to the bill. Being a suspicious sort of fellow, I asked why
the engine suddenly needed to be decarbonised. I was informed, with
a pitying look, that engines gather carbon deposits over time, and
removing them would increase performance and fuel efficiency. Well,
there's no arguing with that, is there? Carbon bad, decarbon good.
But somewhere in my mind, a stubborn bit of carbon lurked, itching
uncomfortably every ten thousand kilometres. Last week, my car was due
for its 20K appointment, and I asked Google “does my engine really
need to be decarbonised?”. One of the top results was a forgotten
silk-list
post where I had asked the same question! Someone pointed me to
this
thread
that discusses the question at length on Team BHP, a well-known car
enthusiasts' web site.
I couldn't find an authoritative answer. Many people swear by the
procedure and claim to have "felt the difference" immediately. Some say
it's needed only after running 40 or 50 thousand kilometres. Others say
you don't need it unless you're using poor-quality fuel. Some recommend
doing it more often if you drive in city traffic. Some say it's better
to flush the engine regularly and forget about decarbonising. Some say
both are necessary, but garages charge way too much to do it. There's a
lot of "my friend told me" advice. All but a tiny minority who think it
is hogwash shell out between 1200 and 2000 rupees to their workshop at
regular intervals for a procedure which is not mentioned anywhere in
my car's service manual, and which depends on third-party
additive kits.
After much research (otherwise known as clicking "Next" on Team BHP), I
declared myself a skeptic and took my car to the workshop fully prepared
to fight for my carbon deposits. To my disappointment, they didn't
prescribe decarbonisation or flushing at all. They listed only perfectly
sensible things like changing the engine oil and cleaning the fuel
injector. I guess they must be waiting for the 30k mark to break the
news to me.
Driving my car afterwards, I felt the difference immediately. The engine
purred smoothly and the car just felt better. I wonder how many of the
carbon cultists on Team BHP were feeling the same thing?