As mentioned in the above post, it is winter rating. 0w can withstand and retain fluidity vs 5W at even lower sub-zero temperature.
You do have a point on 0W30 is better than 10W30 at startup in default. I forgotten all abt that liao until I re-read BobtheOilGuy again. This is however just one aspect of having 0W30 instead of 10W30. Most FS (0W rated should be FS liao coz mineral tak da that rating) here is actually hydrocracked highly refined mineral (Group 3) rather than true Ester or POA based fully synthetic thus VI addictives must be used.
Mineral starting viscosity without VI will rated 0 for OW30 and 5 for 5W30. To thin it further, VI is used to so that that it can reach weight 30 at operating temperature. The more VI is used, the more chances of addictives wearing out thus viscosity will go back to original rating (0 for 0W and 5 for 5W). Thus if the longer you used, the risk is greater that the starting viscosity will slowly moved back to original rating. Once back to original, 10W30 is definitely more thinner than 0W30. So key point, the wider the range between winter rating and normal temp rating, the more VII is used. The more VII used, the faster it will wear out after extended used due to the larger range.
However this is a mute point if you service your car on schedule. Then again, most FS here are 5W or 0W rated, very rare on 10W rated. So if compare 0W vs 10W, you're talking abt FS vs basic mineral, I would take FS anything as long as I can afford it. Anything better than 10W30 mineral due to its synthetic based contents and properties along with much cleaner mineral based stock. So in actual fact, comparing 10W vs 0W here is another mute point.
However there is still debate going on if 10K and above mileage will wear out the addictives for our weather, driving conditions, humidity, dust that tends to contaminate and wear our eo faster than normal (vs most western countries where the articles are from).
Secondly there are also some newer oil tech such as magnatec, even supposedly the new Havoline tech where lube residue will stick to components even during cold start that can minimized engine wear. This all adds up to allow multiple choices to reduce startup wear and choosing the most suitable eo viscosity and brands. So questions is......is 0W30 normal fs better than 5W30 fs with magnetized lube......? I don't know either.
I use FS oil, Syntium 5000 0W30. With regards to Grp III, III+ or IV, I don't really care all that much. What matters to me is the rating of the oil. ACEA ratings, BMW ratings, MBB and VW ratings. You are right about oil change interval. What Proton recommends is good enough for me. I am not confident of going more that 10,000 km even on FS without used oil analysis or having a good oil life monitor like on MBs and BMWs.