Ask the Mechanic: My Toyota Vitz is burning up oil at an alarming rate

Hello Paul, I have a Toyota Vitz 1.3L 2009 model with a 2SZ fe engine. The engine oil level goes down by 300ml every 1,000kms. There is no leakage in the engine or under the car. It is mainly driven in town daily around 20 to 30kms only. The inside of the exhaust is black but does not emit smoke. Please help me diagnose the problem.

Zahir.

Hello Zahir, if there are no visible external leaks, the oil is probably being burned inside the engine, most likely because your piston oil rings are worn or cracked. That would not be unusual with a small engine that is 13 years old and might be well on the way to 200,000kms. Have the compression tested and stand by to replace the piston rings.

 Your oil loss rate translates to a mixture of about 200 parts petrol to one part of oil (200:1). Many two-stroke engines operate on mixtures at least four times as rich in oil as that, so your exhaust will not necessarily be smoky in normal use.

Try the check again. Watch the tailpipe while someone else presses the accelerator pedal to the floorboards, just for a second or two, to momentarily hit top revs. Do that two or three times in quick succession. Still no smoke?

The only other possibility is that the oil is leaking through a crack inside the engine block into the coolant channels in its walls. In that case, there would be oil visible in your radiator coolant, and the remedy for that could be more complex and expensive. Your rate of loss does not portend imminent engine failure but is high enough to warrant a check soon and probable remedial action.

HOW BAD IS IT TO DRIVE ON AN EMPTY TANK?

Hello Paul, how far will a vehicle on average travel after the low-fuel warning light comes on and are there any dangers of driving with an almost empty tank.                     

Clement

Hello Clement, fuel gauges are not accurate and the fuel can slosh about in the tank, so the low-fuel warning light level can also be approximate and erratic.

The level set to trigger the warning light varies between different makes and models but is usually at about four litres. Assume not more than that and possibly less. The main danger is that you will run out of fuel before reaching the next filling station, or that the next station will be out of stock.

The principle is that you should refill as soon as possible, and if you are in a particularly remote place, drive as economically as possible.

That means avoiding harsh acceleration or high speed and cruising smoothly at around 60kph in the highest possible gear without labouring the engine.

A possible but unlikely danger is that debris that may have accumulated in the bottom of your tank will be stirred up, so the engine might be drawing on dirtier fuel.

Always consider refuelling when the gauge reaches the quarter mark or sooner.

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