Sale moved to the brink of qualifying from Pool One of the Heineken Cup as they eased past Castres with a bonus-point victory at Edgeley Park.
Sebastien Chabal went over either side of the break as the Sharks maintained their 100% record in the competition.
Jason Robinson bagged a second-half try to cap off a superb all-round display, while replacement Robert Todd also touched down late on.
Fly-half Charlie Hodgson was again solid with the boot, kicking 15 points.
Castres full-back Romain Teulet notched the French side's only score, replying to Hodgson's opening penalty.
Hodgson kicked two more penalties for 9-3, and a scrappy first half only really came to life when French international Chabal went over in the right corner.
He then intercepted a pass and galloped 60 yards for his second on 43 minutes.
Sale skipper Robinson completed good work by Mark Taylor, coming in from the left to scurry over, and Hodgson was on target with all three conversions.
Sharks chased a bonus point in the final few minutes and got their reward when Todd got on the end of a length-of-the-field move involving fellow replacement Chris Mayor, Hodgson and Magnus Lund to crash over.
Victory over Newport-Gwent Dragons in their next European match in January should see Sale through to the quarter-finals with plenty to spare.
"Before the game I would have taken a win and four tries, but it wasn't our best performance.
"We lost a lot of ball in contact and we weren't patient enough but what is good is that we can improve 40% from this.
"Sebastien Chabal fits into our gameplan and our system very well, and he is a very important player for us."
Sale: Larrechea, Cueto, Taylor, Seveali'i, Robinson, Hodgson, Martens, Sheridan, Bruno, Turner, C. Jones, Schofield, White, Lund, Chabal. Replacements: Titterrell, Stewart, Coutts, Lobbe, Courrent, Mayor, Todd.
Castres: Teulet, Milford, Raffault, Christophers, Ropati, Delaigue, Albouy, Forestier, Romieu, Attoub, Ghezal, Capo Ortega, Froment, Bernad, Taussac. Replacements: Vigneaux, Hoeft, Castex, Nallet, Puricelli, Fior, Montoro.
Referee: Malcolm Changleng (Scotland)