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Compression lesson

What to do when you engine suffers a "blow-by"

Hi, Ferman!

I love your column a lot, as it teaches newbies like me very important matters about how to handle cars the right way. So now I’d like to ask for help. Based on the info that I gathered online, smoke coming out of the oil dipstick slot means your engine has suffered a “blow-by.” The engine of my car, a 1989 Mitsubishi Lancer, shows this sign. I would like to ask how I can remedy the situation. Also, I want to know if there are preventive measures so I can postpone the inevitable and overhaul the engine. My car still runs perfectly, but I want to wait a few more months before overhauling the engine due to economic reasons.

I hope you can help me. More power to your section and Top Gear! I hope you release a book on car maintenance--or do you have one already?

Francis Gonzales

Hi, Francis!

I’m glad you like the section and find it helpful. It’s readers like you who encourage us to do our best. In your case, a compression test can help determine if you really do need an overhaul or not. Small variations between cylinders are okay. Larger variations mean that you may need the overhaul sooner rather than later. Based on what you’ve described, I wouldn’t be in a rush to rebuild the engine unless smoke is coming out of the tailpipe, or emissions have become really bad, or the car’s drivability has started to decline.

I’ve encountered four-cylinder engines with two of the cylinders having significantly lower compression readings than the other two, but with the power and emissions still fair and decent. The cost of having this problem fixed is going to be about the same whether you do it earlier or later.


I used to have one of those Lancers, and the engine can take a fair amount of beating as long as you don’t abuse it excessively. And compiling this section to make a book sounds like a good idea.

Ferman Lao
Technical editor

Source: Top Gear Philippines, April 2009

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