A real weakness but quite misunderstood and exaggerated. It is true that China is quite vulnerable to an oil blockade. But there are a few things people miss.
1- Malacca isn't very important. It is used because of the infrastructure provided by Singapore and its closeness to the Asian mainland. There are many bodies of water there. In fact, the largest oil tankers already avoid Malacca because of its shallowness. The assets the US needs to blockade China are quite substantial in amount because of this. This means a lot fewer assets to deal with in China's periphery
2- It would have no effects on Chinese war making capability, heating and electricity production. China produces a lot of oil and heating is usually done using coal. Transportation would be hit. But that's about it.
Depending on when this happens. Domestically, a large portion of domestic bus fleet and taxis have already transitioned to EVs. NEV % in China this year is basically going to be in the high 20s and that number will get to about 50% in the next couple of years. As such, if a conflict takes place later part of this decade, there is very little hit if they just forbid people from driving ICE cars. Sure, people might complain that they can't drive their ICE cars, but they just need to suck it up.
They can get about 7 million bpd from domestic production and Russia. That's plenty for war time economy when they can cut ground transportation by 90% and civilian air transportation by 95%. If we add in pipeline from Myanmar and truck based transportation from central Asia, they will have no issues here.
I have also looked at LNG supplies. With power of Siberia 1 and 2 coming online, but additional pipelines, they have probably 80 to 90% of their need covered from domestic production, pipelines and Russian LNG carriers.
They have so many clean energy projects coming online in the next few years that electricity generation isn't going to be a problem. They have a lot of underutilized coal plants that can always get more utilization if needed. Russia can export them plenty of coal also.
3- Most people miss it but modern navies are not suited for either blockades or merchant escorts. They grew too small for that. Unless the US engages in unrestricted warfare against merchant marine I can't see how they could accomplish an effective blockade.
They would have no way of knowing whether a ship is going to Korea or Japan or asean countries. I guess they could just blockade everything, but that has its own costs.
4- Blockading China equals blockading the entire world and a blanket blockade on SCS and the Persian gulf would break the global economy. It would have huge political costs for the USA.
In a war of hegemony, neither America nor china would care about that. Frankly, I have suggested that china could threaten to destroy refineries in middle east if European countries get too anti china in a conflict.
5- Most US patrol assets, which would be spread thin because of the geography, would be vulnerable to Chinese surface groups and conventional subs. Yuan is not a coastal sub after all. Only American assets that are under aircraft carrier coverage would be safe.
Which is why it will be china that enforces all the blockade. They have a huge coast guard fleet along with a lot of 056s that could be used for this purpose. Any oil tankers from America to Japan would get intercepted by Chinese coast guards after the first week or so. Any ships from Australia or new Zealand would have to pass through china controlled areas to east Asia. So as long as china can protect it's assets in scs and east china sea, they control the action.
I would be curious what
@Patchwork_Chimera thinks about this. If we go by the scenario that china is able to significantly degrade American military bases, 7th fleet and JSDF in the first few days, then would the coast guard be heavily utilized by china to enforce it's version of justice.
Again, I am not suggesting china will be the good guy here. It will likely be as brutal as it can be to gain advantage in the surrounding areas. It will probably pressure Philippines, Malaysia and Thailand to use their military bases to conduct attacks.
Myanmar and Cambodia are likely to be helping china in any conflict by allowing china to use their military bases. This would allow them to deal with the threat of America launching attacks from Diego Garcia and Australia. Again, I am just looking at things from Chinese perspective. If they are able to knock out american and Japan forces in the first week, that would change a lot of nations perspectives quickly. China would be really able to pressure them to pick china for the duration of conflict. I am sure America will try to pressure these countries to go the other direction, but they will fear the weight of Chinese military a lot more. That's kind of the issue facing America helping Taiwan here. If it's bases get significantly degraded in the initial attacks, it's allies in the region will be left alone and neutral countries will likely cut deals with china.