I currently own a 2010 Honda Civic 1.8L and a 2012 Honda Jazz(Philippines) / Fit (USA and Japan) 1.5L. I just purchased a second hand Jazz/Fit about 2 weeks ago and the mileage is 32xxx. Btw we use Kilometers and Liters.

Upon getting the car. The reading is 8.5km/L according to the multi gauge display. So it was okay okay to me but the usual reading that I've researched from other jazz/fit owners was 9-11 km/l on city driving and about 12-14 km/l for highway driving conditions.

So I was a bit bothered for its fuel consumption so I replaced the engine oil with Honda Lev Fully Synthetic, OEM oil / air filters, Iridium Spark Plugs (Denso), replaced the transmission filter and ATF by Honda. And also I replaced the 4 tires because the tread is about 40-50%.

Upon replacing it I was surprised that I'm getting 7.5km/l on city driving. It actually went down from the 8.5km/l and its supposed to be fuel efficient because I just replaced the needed parts.

Any recommendation or advice that I need to do?

Thank you everyone!

2 Answers 2


You may try unplugging the battery for about 30 minutes. This will reset the computer. Also, carefully clean your MAF (if so equipped) with electronics cleaner. Do this before you plug your batter back in. The reset will help the computer relearn from factory settings and may improve your gas mileage. Cleaning your MAF is just preventive maintenance which could also help the computer read the correct amount of air intake.

If these two steps fail you, check to see if there is an exhaust leak before the upstream O2 (lambda) sensor. You'd be looking for suet around areas where the exhaust system comes together (such as where the exhaust manifold meets the head on the engine). If you see anything like this, the engine is getting air into the exhaust system, which is giving a false lean condition, which tells the computer to dump more fuel to make up for it.

You can also check your O2 sensors to see if they are lazy, but with such few miles (KMs) on the clock, I doubt this would be an issue. Lazy O2 sensors can cause the system to dump more fuel as well, as the O2s cannot keep up with the demands and give false readings to the ECU.

  • How do you identify if your O2 sensor is lazy? Commented Dec 16, 2015 at 19:49
  • You have to take a reading from the DLC port or do some data logging. When you look at the data log for the O2 sensor (pre-cat only), it should be all over the place. If it isn't, it's lazy. IIRC, O2's should read between ~.100 mv and .900mv. When you are looking at the graph it should be jumping around between the two numbers non-stop. If it appears to be lackadaisical in its meanderings, it would be lazy. It gets this way before it goes bad, but can be like it for a while before the ECU sees an issue. Commented Dec 16, 2015 at 22:15
  • 1
    I'm probably going to turn this in to it's own question. Nice way to be proactive if your a geek. Which I am. TY Commented Dec 16, 2015 at 22:17
  • A lazy O2 will still flit between rich and lean. It just doesn't respond as quickly to change
    – Zaid
    Commented Dec 17, 2015 at 18:53

Try a specialist fuel additive like Wynns catalytic converter & lambda cleaner, if you have a dirty lambda sensor that's the cheapest & easiest solution.

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