thank you, i try to help to the best of my knowledge.
10W30 & 5W30 oils are rated from Arctic climates to moderate climates, that means that in our tropical climate these oils will reach their flash point and over time the level of oil will decrease in the sump as some is burned away in the combustion process. (see image attached below)
i understand your logic though, and i think ideally it'd make sense to use 5 or 10W30 in winters and 20W50 in summer (in an ideal world). However since pakistan does not experience arctic climates (generally) it's make sense to use an oil which is more suited for the environment in which it is to be used in. 20W40 & 20W50 is indeed thicker than W30 oils which will lead to a momentary lack in viscosity in cold starts in winter but as soon as the engine reaches optimum operating temperature all these oils will perform well. however since most of our engines tend to run hot in PK due to stop-go traffic and inefficient cooling systems we must take precautions and use a better suited oil.
hondas use a synthetic oil which is great for retaining its TBN and suspending particles but i can challenge anyone to prove me wrong that in peak summers a civic VTi will not burn a little oil during normal operation (when using hondas own oil which is blended by total). I have been conducting tests on various grades and brands of oils, in most applications (CD70 all the way till Hino trucks) and i've fould that diesel cars have better cooling setups and can run on 15W40 (industry standard in PK) and 20W50 in passenger cars while retaining a little safety margin.
Petromin & Fuchs both offer a superior oil with high flash points, high TBNs and the correct additives for our local market,.. and they are cheaper or at least on par with the competition (in terms of price).
I must add that ther eare 2 schools of thought, 1 is to use synthetic and enjoy for 10000kms and the other is to use a mineral and change it every 2500. i find both to be wrong. i say why not use an oil with the benefits of a synthetic with the price of a mineral and then change it at 5000km?
this is why I've become a fan of Petromin & Fuchs oils. BTW honda pakistan did a deal with total only because they could supply then with the cheapest oil, not because it was the best,.. and honda is already looking into solutions to a problem they are not admitting. VTi's (high-revving engines) are burining oil, ask any honda owner who has used the new oil and they will say that as the temp is geting hotter their cars are drinking more and more oil. i'm not bad-mouthing total though,.. the oil is an ideal blend for most modern engines,... in europe!
(sorry for the long reply)
