CAAM made the statement in response to a plan on vehicle emissions control, now being drafted by the Ministry of Environment Protection. Under the plan China 4 emissions standards, which are on par with Euro 4 standards, will be applied across China to heavy duty trucks in January 2010 and to light vehicles in July 2010. 

"For one thing, the quality of existing fuel oil cannot ensure the implementation of China 4 emission standards. For another, it will cause emissions to fast deteriorate and reduce product life if vehicles are forced to adopt advanced emissions technology when fuel oil quality falls short of requirements," CAAM says in the open letter.

To date, only two major cities, Beijing and Shanghai, have enacted the China 4 vehicle emissions standards. Motor vehicles in the rest of China are still subject to China 3 emissions standards, which are the Chinese equivalent of Euro 3 standards.

Instead of enacting China 4 standards prematurely, what the government should do is make sure China 3 standards are effectively enforced across the country, says CAAM.

CAAM also said it submitted the letter to the Ministry of Environment Protection earlier this month.