A quart of oil is not just oil. Up to 25% of a quart of oil is comprised of its additive package, which are a group of chemicals designed to help the oil do its job. How the additive package of a motor oil is formulated can vary greatly from oil brand to oil brand and account for distinct differences in how a given motor oil brand performs/does its job or not. Pour point depressants aid the oil in pouring better in the cold, dispersants to keep dirt suspended in the oil so it can be filtered out by the oil filter, anti-foaming additives to help the oil resist foaming, detergents to help keep the inside of the engine clean, etc., etc. A quart of oil is a precisely measured combination of a host of different chemicals and when we then use a pour in oil additive, this upsets the delicate chemical balance of the motor oil and can have unplanned and negative affects that will not be covered by the oil manufacturers warranty or the vehicle manufacturers warranty. An expensive risk.
It's similar to a cake recipe that say calls for 2 eggs. Adding 2 more eggs to the recipe wont make for a better cake, it will
ruin the cake. It's all about the balance of the ingredients working together, or in the case of a motor oil that has been carefully formulated by a highly trained and educated chemist/tribologist, the additives/chemicals that
are already present in that quart of oil you purchased down at the discount auto parts store.
Another aspect to consider is that even if the pour in oil additive were not to harm the engine, what about the expensive oxygen sensors that are mounted in the exhaust stream? What about the many times exceedingly expensive catalytic converter? Motor oils are formulated to not cause damage to these expensive components when the motor oil is consumed in combustion and sent out into the exhaust, but pour in oil additives? An expensive risk.
You may note from your vehicles owners manual that it specifically
warns against the use of pour in oil additives, warning that any subsequent engine damage will not be covered under warranty. From my observations the only ones recommending any of these pour in oil additives are the companies that are trying to sell them to you and the late night infomercials with someone wearing a white lab coat, a chemist in a box. Consumer beware!
Below is a 5 minute video that discusses some oil basics and what makes an oil a synthetic oil that will provide a bit more information on this interesting and often misunderstood topic.
If anyone has any questions, please feel free to ask me. I'm an Independent AMSOIL Synthetic Lubricants Dealer of close to 30 years experience. I offer my customers the guaranteed lowest prices.
