Poor fuel quality. Incomplete combustion and lack of sealing between piston and cylinder wall or badly losing valves. Possibly incorrect engine timing / set up.

燃油品质差，不完全燃烧和活塞与气缸壁之间的密封性差。 。

youdao

That supposedly helps the poor. But Fatih Birol, the IEA's chief economist, says that the subsidies mainly benefit middle-income and higher-earning urban types; the rural poor use little fossil fuel.

发放补贴本是为了帮助穷人，但国际能源机构首席经济学家法提赫•比罗尔指出，得益于这些补贴的主要是城市里的中等及高等收入群体；贫穷的农村人很少消费化石燃料。

youdao

The World Bank estimates more than 100 million people became poor when food and fuel prices skyrocketed last year.

世界银行估计，大约有超过1亿人在去年的食品和燃料价格急剧上升时陷入了贫困。

youdao

It also cites predictions there would be three million "poor fuel" households by the end of 2006.

BBC: A pensioner by a heater

The proposals would also enable the gas distribution companies to connect around 80, 000 "poor fuel households" to the gas network for the first time, and pay for carbon monoxide awareness programmes.

BBC: Energy bill rises not enough, says National Grid

In fact, programs that help the poor afford fuel have been identified as the largest category of fossil fuel subsidies in the world.

FORBES: Understanding Subsidies