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I bought a pre-owned car that's gulping more fuel than it should

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Motormouth Online

Hi, sir Ferman! I bought a secondhand 2005 Nissan X-Trail 2.0 as our first car. I decided to buy it because I was impressed with its looks (black color, 17-inch wheels, HID head- and foglights, rear spoilers, modified chin bumpers, double mufflers and free car amplifier).

At first, I observed that its fuel consumption was about 7-8km/L, pretty good for a secondhand vehicle. It had its first oil change at Petron seven months after I had purchased it. After a month, the X-Trail had issues. I noticed that the vehicle would slightly turn left even when the steering wheel was on center. It needed a crank sensor repair and new brake pads. The vehicle would rapidly gulp more fuel even when the A/C was only set to number two.

I also observed its fuel efficiency became 5-6km/L despite driving smoothly. I am now planning to sell it, but its pristine appearance is making me hesitate to let it go. If I have to retain it, what are the things I need to consider and repair to optimize fuel efficiency?

I hope you can help me. Thank you in advance and more power to Top Gear Philippines!

Win Prieto


Hi, Win. I'll have to make certain assumptions about your concerns as your letter lacks some details about your X-Trail. Let's take a look at your concerns individually.

1. Purchasing a secondhand car. When you buy a pre-owned vehicle, you should be able to accept certain things. One of those things is the fact that you will have to spend for repair sooner or later. In your case, you likely just reached that mileage point wherein the parts were due for replacement.


Brake pads, for example, are wear-and-tear components. You should expect to replace them anywhere from 20,000km to 30,000km, or much less if you do a lot of heavy urban traffic stop-and-go driving or very spirited driving, particularly in a vehicle with an automatic transmission. When you replace your brakes, don't forget to have your rotors refaced or replaced as the case may be. If they're within 1mm of their minimum service-life thickness, go ahead and just replace them. There are enough replacement rotors available on the market, so in some instances it makes more sense to replace them. If you don't reface them when you install new brake pads, you're only shortchanging yourself, as the usually uneven worn rotor surface will not give you the best braking available with your new pads. They'll also induce uneven wear to your new pads, exacerbating the problem.

2. Oil changes. As long as you use the correct recommended-viscosity oil, you'll be fine, but a better oil will always give you better protection and mileage. Several brands are available and you can choose whichever fits your budget. The type of oil you use does have an effect on fuel consumption. You'll need to try which one works for your engine. The best gauge when selecting the best oil for your engine? Your ears, butt dyno and fuel consumption. The engine will sound and feel smooth. Your vehicle will also deliver better mileage. Find out which oil the previous car owner had been using if your fuel consumption significantly dropped after your oil change. Then switch back to it.

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But wait, there's more to that.

3. Crank angle. You mentioned you had your crank angle sensor repaired. Is it replaced or "repaired"? As far as I know, it isn't possible to repair unless something else was done and you were just told that it was repaired. Check your receipt. Which begs the next question: Why did it have to be repaired? Misfiring...engine won't start...check engine light came on--those details would've been helpful. Without them, the information about the crank sensor being repaired is incomplete.

4. Increased fuel consumption when your A/C is turned on to the number two setting after the repairs. The fan speed does not have as significant an impact on fuel consumption as the temperature setting. A colder temperature setting will keep the compressor on for much longer with the accompanying increased load and fuel consumption. That said, if your increased fuel consumption coincides with the change from cold to warm weather conditions, I would attribute the increased fuel consumption more to the change in season rather than the vehicle repairs. The weather becoming much warmer is a factor as the A/C compressor has to stay on much longer as well.

Your X-Trail's color (black) is also a factor, as a black car can become warmer inside by five to six degrees Celsius more than an equivalent white- or silver-colored car. Five degrees Celsius is a lot. Note that the difference between feeling cool, warm and hot can also be thought of as 20 degrees Celsius, 25 degrees Celsius and 30 degrees Celsius. The difference means that, again, your compressor has to stay on that much longer and consume that much more fuel.


5. Car drifts left when the steering wheel is on center. Did you have wheel alignment when you had your oil change? If you did, just ask them to center the steering wheel so that the vehicle tracks straight when the steering wheel is pointed straight. It's a simple (although somewhat tedious) task, even if your auto technician knows what he's doing. Or you could check your tire pressure. A 2psi difference between the left and the right tire can cause a slight pull to one side, and too low a tire pressure can increase fuel consumption as well.

Did one of your wheels take a bad hit at a pothole? It could've caused your alignment to go out of spec. Badly aligned or cambered wheels can cause as much as 1km/L drop in fuel mileage.

6. To sell or keep the car? Finally, should you sell it because of poor fuel consumption, or keep it because of good looks? If you're definitely sure that your X-Trail is consuming more fuel than usual, it's going to be your personal choice on whether you want to live with the poor fuel consumption that goes with the styling that makes you feel good. I doubt, however, that you'll feel good for long unless the fuel consumption improves to your expectation. It's like wearing sharp shoes that are uncomfortable and make your feet hurt. Pretty soon, you'll stop wearing them no matter how good they look.

Best regards,
Ferman Lao
Technical Editor


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