1 – the engine oil level was not checked and it might be insufficient to ensure complete lubrication and sufficient engine oil supply at the fixed flow. In this case you should switch off the engine immediately, wait a few minutes for the lubricant to flow back to the oil sump and then check its level. If the engine oil level is too low it should be topped up with the suitable or similar engine oil by adding it in small portions - a large top up may cause a thermal shock. The optimum engine oil level should be between the upper and the lower mark on the dipstick. However, if it turns out the lubricant level is significantly higher than the upper mark (and it is significantly higher in comparison with the previous measurements), it means there is some problem with the engine:
- if the engine oil is not cloudy or milky, it probably was diluted with unconsumed fuel and the car should be taken to the service station for repair,
- if the engine oil is cloudy or milky, it means there is a problem with sealing of the engine cooling system or gauge head and we won't go away without a visit at service station either. In both cases further use of the engine is not recommended.
2 – situation when the warning light goes on at idle and goes off on higher engine revolutions might be typical for low-viscosity engine oils economizing the fuel, when used in cars where the engine oil pressure sensor was adjusted to regular viscosity lubricants. In this case control of the oil pressure sensor is recommended. Low-viscosity lubricants such as 0W-X or 5W-X, when compared to regular 10W-X or 15W-X engine oils, might induce lower pressure in the lubrication system at low engine load and low revolutions. For example, in the case of Fiat 126 which has long been using 20W-40 engine oil, a change to 15W-40 lubricant may induce this effect.