AUTO TALK: Problems with fuel tanks and fuel gauges


The average life of a car in Thailand is about 12 years. The first owner usually uses the vehicle for about five years, while the second owner has it for three before it is sold to the third and fourth owners who use the car for about two years each.

However, some cars are used longer than that, and generally after seven years problems will start to show up, especially electrical problems that are hard to spot with the eye. Moreover, certain parts in places that are not usually visible can start to rust.

For example, if the engine doesn’t run smoothly, the mechanic will usually replace the fuel filter.

But that may not get rid of the problem, and when the owner returns to the garage or service centre, the mechanic might attempt to replace the fuel filter again, even though it isn’t the cause of the problem. Or he may focus on other systems that require costly parts replacements, and this often leads to even-greater damage than the original problem.

Khun Duangjai from Chiang Mai has had such a problem, as follows:

I use a Mercedes-Benz C220, which I bought as a new car at the end of 1996 and the mileage is now 98,000km. The problem happened while driving uphill – the engine just stopped and wouldn’t start. I went to my regular garage and the mechanic said the fuel gauge was broken and needed to be replaced at a cost of Bt3,700 per side.

I want to know what causes the fuel gauge to be damaged – is it because I use gasohol 95? (I have been using gasohol for three months.)

Another mechanic advised that if I put in a fuel additive called **** (name of product withheld), it would help prevent the engine from stalling when going uphill since it helps improve combustion and produces more power. Is this true?

Don’t put the blame on gasohol – most of the problems with the fuel gauge are due to impurities in the fuel you put in. Certain gas stations are not careful with the cleanliness of the underground fuel reservoir.

Some never clean the bottom of the tanks, even though the stations have been open for 10 years. Some stations are located in areas frequently hit by floods and water can make its way into the tanks, forming a slimy substance.

This slimy film will clog the fuel filter or can damage the mechanism of the fuel gauge. But if the fuel gauge isn’t working, the engine should not stall, since the only damage that should occur is that you can’t tell how much fuel you have left.

Considering the symptoms you mentioned, I believe the problem stems from the impurity in the fuel. Although the fuel filter has been replaced, if you experience the same problem again I recommend that you thoroughly clean the fuel tank before getting a new fuel filter.

This will help remove all the impurities from the fuel tank once and for all.

Otherwise you will have to keep on changing the fuel filter again and again.

For the second question, I don’t want to mention the name of the fuel additive because I don’t want to start a quarrel with the company that sells the product.

But if fuel additives were really that good, I guess a lot of mechanics would lose their jobs. Just make sure that you fill up with clean fuel and select the right octane level for your car, and that should be adequate in ensuring optimum performance.

For your C220, I suggest that you fill the tank whenever the fuel level drops to about one-quarter of a tank – don’t let the level drop lower than that. Also, turn off the engine when refuelling.

If you regularly leave too little fuel in the tank, apart from the fuel gauge the fuel pump may also be easily damaged.

Turning off the engine is also a safety matter, since if there is a fuel leak while filling the tank and the engine is running, there are chances that a fire could start.

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