how can i fix my girlfriends pug?

my girls got a old g reg 205 pug 1lr sh*t heap not worth alot but its a good cheap runner anyway it past its last mot and the bloke said it wouldnt pass again due to the blue smoke coming out of the back end when the engine is accelerating can i do anything to stop this ie is there an additive or somthing i can put in the engine or flush it out that wil stop this or is it destined to the scrapy any help would be great cheers