The rituals of automobile worship

By Abhijit Menon-Sen <>

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?