Someone must already have covered this but we thought we would share some information in a question and answer format. Our own contribution to clearing the confusion on the oils we really should be using on our 1998 - 2016 Hondas, Nissans, Toyotas, Kias, Lexuses, Hyundais, Acuras, Suzukis, Mazda, Fords, Land rovers, Chryslers, etc. Why oil and good oil is necessary The life blood of the engine is the oil and using the wrong oil translates to a reduction in performance. A well run engine allows all other components to work efficiently e.g air conditioner. alternator, gear system, etc. Using any oil other than that specified by the engine manufacturer robs you of performance. We are not talking about you driving faster than the speed of light but you maximizing the full potential of your engine in terms of smoothness, quietness, fuel economy, efficiency, and long life. What does 5w-20, 5w-30, 10w-30, 5w-40, and 20w-50 mean ? Oil is categorized in viscosities or in lay terms weight. 5w-20 for example is thinner and will flow better than 5w-30 which in turn is thinner and will flow better than 20w-50 and so on and so forth. Thinner oils are not good for hot climates First of all the oils are inside the engine where temperatures rise to as high as 200 degrees Fahrenheit compared to a maximum of 120 degrees Fahrenheit for the ambient temperature in hot countries. This alone tells you that ambient temperatures in hot climes is no longer the major factor or determinant in the selection of oils today. If it were then such information will be clearly stated in the owners manual. Why do some manufacturers use 5w-20 and 5w-30 oils Traditionally 20w-50 has been the oil of choice but as the years have gone by most manufacturers have had to respond to calls to make their cars more fuel economical as petrol / diesel pump prices have risen globally. Car manufacturers after spending millions on research and development have discovered that by placing less strain of the engine moving parts e.g pistons, valves, etc they have been able to generate more power from the same cars. This has led to the reduction in engine tolerances and introduction of thinner oils ( 5w-20, 5w-30, 10w-30 ) to allow engines operate freely without drag. What is wrong in using 20w-50, 15w-40, 5w-40 etc in an application calling for 5w-20 or 5w-30 Because the internal spaces and engine tolerances have been reduced 20w-50 is just too thick to be able to pass through the thin spaces between metal moving parts and provide adequate lubrication. This results in engine wear over time. One of the reasons why we see cars that are less than 6 years old in this country smoking. They have simply been using the wrong oil viscosity ( either 20w-50 or 15w-40 as against 5w-20 or 5w-30 ) from inception. Using 5w-20 and 5w-30 oils is not good for my car Car manufacturers make cars and sell to the public. These cars are covered under a warranty which must be honored by the manufacturer. It makes little or no financial sense for a manufacturer to recommend an oil viscosity that might destroy an engine that this same manufacturer will have to replace at his own cost. Are all 5w-20 and 5w-30 oils the same? Absolutely not. What differentiates one 5w-20 oil from the other is the quality of base oil and additives used in arriving at the final product. A 5w-20 oil using better base oil stock and an average additive package will be better than another 5w-20 oil using the same base oil stock and less than average additive package or lower base oil stock and same additive package. The formulations differ and that is why you notice a difference is performance when you change oil brands. We hope you find the above helpful and for those who are interested please be advised that Milemaster 5w-20 and 5w-30 synthetic oils are available from www.milemasteronline.com. Same day delivery for Lagos residents !!