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| Some Myths about Engine Oils |
| Myth |
Fact |
If the oil turns dark or black quickly, it has degraded and needs to be changed. |
Engine oil cannot come out of an engine looking clean at oil change. The oil is in fact doing its function of cleaning the engine, and hence it should look dirty when it is drained. In the case of diesel engines, the oil can look dirty within a few hours of operation. The oil is doing its job of keeping soot, dirt, and other combustion contaminants in suspension to be carried to the filter or removed from the crankcase when the oil is changed. |
| Red oil is better than natural golden colored oil |
No, since the red colour is caused by a dye and not by any additive or any oil related input. |
| I am comfortable using SAE 40 oil, why should I use a multi-grade oil like SAE 15W 40? |
Multigrade oil is oil whose viscosity properties have been changed artificially in order to slow down its rate of change of viscosity with temperature. Thus such oil tends to be thinner at low temperatures and thicker at high temperatures than monograde oil.
There are several benefits one may expect of multigrade oil.
- When a vehicle is at rest for a few hours, all the engine oil comes down to the oil sump. Thereafter, when the vehicle is started, there is a certain time (probably only microseconds) before the oil reaches all the parts of the engine once again. Since the multigrade oil is thinner at low temperatures, it reaches all parts of the engine quicker than monograde oil and hence, reduces wear to that extent.
- Generally, it has been observed that use of multigrade oils enables better fuel economy of 1.5% - 3%.
- Multigrade oil offers better protection to the engine at high temperatures than monograde oil, since it is thicker than the monograde oil at temperatures above 100OC. This is so even if the multigrade oil is thinner than the monograde oil at temperatures below 100OC. This property of multigrades also reduces oil consumption.
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| The used oil smells burnt, the oil is bad. |
If the oil smells burnt, it is possible that some fuel has contaminated the oil. If the oil also feels thin, it can be tested at an oil lab for verification. The oil needs to be changed only if there is substantial fuel dilution, resulting in a viscosity drop of greater than 15% of its original value. If the viscosity drop is not so substantial, the oil can continue to be used, as a certain amount of fuel dilution (below 4%) is not abnormal. The truck owner should however be informed about this fact and advised to get his truck engine checked. |
| It is correct to add oil to a fuel tank in a four-stroke engine vehicle |
No, because the oil is not easily burnt and tends to leave a lot of deposits on the engine parts preventing it from functioning well. |
| Additive "supplements" available in the market increase engine power or extend the oil drain interval. |
In general, these products are a waste of money, and if used incorrectly can result in engine damage. Today's oils are manufactured using a complex additive package which does not require the use of additional additive products. You should use the recommended oil for your vehicle that was manufactured to meet the latest API specifications. |
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