This article may seem like going back to the basics but I am always surprised by the number of people who do not understand what’s written on a gallon of oil, and therefore, have no idea what they are buying or using. This week’s discourse about oil grades aims to enlighten us more about what specification of oil to use. To be blunt about the subject, if a gallon of oil does not contain the following basic information, then do not buy it:- the purpose for which it is intended (i.e. motor oil, gear oil).- the viscosity (i.e 10w40, 20w50, 5w30, etc)- the specifications that it meets (should contain both API and ACEA ratings).- the OEM approvals that it carries and the codes (i.e, MB229.3, VW503.00, BMWLL01, etc).
Most oil on the shelves today are multigrades, which simply means that the oil falls into two viscosity grades – i.e the popular (20w-50). In a 20w-50 engine oil, the 20w bit (w = winter), means that the oil must have a certain maximum viscosity/flow at low temperature. The lower the temperature, the better the oil’s cold temperature at cold start performance. The 50 in a 20w-50 means that the oil must fall within certain viscosity limits at 100°c. This is a fixed limit and all oils that end in 50 must achieve these limits. Once again, the lower the number, the thinner the oil. A 30 oil is thinner than a 50 oil at 100°c. Your owner’s handbook will specify whether a 30, 40 or 50 grade oil is required.
1. Is it okay to switch engine oil weights from, e.g. a 5w20 to a 10w30?
It depends. Some vehicle manufacturers provide a range of recommended motor oil viscosity grades based on the outside temperature in which the car is driven. Other manufacturers recommend the use of only one motor oil viscosity grade. For best engine performance, always follow the manufacturer’s recommendation found in your vehicle owner’s manual.
2. Is it okay to use the popular mineral based 20w50 in a car when the manual calls for a synthetic formulated 5w30?
It is not recommended to do this. Using a heavier 20w50 grade than recommended may cause a decrease in fuel economy, higher engine loads and eventually shortened engine life. The only condition in which a heavier 20w50 can be used in place of a 5w30 is mainly when the engine oil reduces. Upon inspection, the owner might be asked to switch to a heavier grade.
3. Is thicker oils better?
In some circumstances, thicker oils can be used to compensate for increased bearing clearances (gaps between bearing and rotating shafts) that have developed over the years. A large change in bearing clearances can result in poorer lubrication. Note: Apart from using the right grade of engine oil, it is important to also use the right class of oil certification. For example, if your car specifies 5w30 API, using a 5w30 API SE will be a bad choice.
Written by Adeniyi Balogun