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Message: <blockquote data-quote="adnoc" data-source="post: 138872" data-attributes="member: 2105">perhaps understanding the connection between the four main factors that makes one engine oil more superior than the other is relevant:1) base oil used (Group I, II, III, IV, V) 2) SAE grade3) API rating4) ability to clean and suspend soot and carbon (detergency level)it has been an issue of which engine oil is better mainly basing on recommendations, advertisements and testimonials...however other factors like driving habits, fuel economy, condition of engine, willingness to pay, brand name, performance, and lots more are also to be considered when choosing a suitable engine oil...1) the base oil used determines the engine oil to be mineral or synthetic, and in synthetic there are PAOs, ester and other base....2) the SAE ratings determines the viscosity of the oil, and perhaps there's a myth about a 10W/30 weighted oil not suitable for our malaysian weather... the thinner the oil will improve fuel economy, lower oil pressure, and better responsiveness for the engine, however as one of you mentioned, if the engine condition is bad, then the need for higher viscosity is advisable to prevent loss of oil due to worn off piston rings, valve seals and seats, oil seals and etc... perhaps one wud need to consider to repair the mentioned parts.... but with a precise and high technology engine designer and manufacturer like BMW, the SAE weight of the oil is "the thinner the better", narrower SAE weighted oils such as 10W/30, 5W/20 are more resistant to oil shearing and the film strength is superior as it requires lesser VII to be blended....3) API ratings are internationally acknowledged to be one of the best and accurate guide when choosing the oil.... later engine models require higher graded API ratings due to the performance level and the environmental issues.... the API ratings are backward compatible, hence, if it is recommended to use SL, you are advised not to use lower than SL, but if it is recommended to use SG, then one can opt to go up to SJ, SL or SM....4) another important feature of an engine oil is its ability to clean and suspend soot, carbon and by-products created in the process of internal combustion until the next OCI... an important factor is the TBN (Total Base Number) level... the ability for the oil to neutralise acid (by-product) created from the internal combustion process.... the higher the TBN level (eq: 10) the better and longer lasting the oil is to withstand the acid attack..... however, the TBN will deplete over time, and once fully depleted, the oil will not be able to neutralise, hence the oil will turn acidic, perhaps sludge and thicken.... affecting the health of the engine....cheers</blockquote>

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