If you take your car to jiffy lube im gonna drive down there and slap you with a stupid stick, they are just kids that have absolutely no idea how to work on a car. Not to mention they use Pennzoil products which are bar none the worst lubricants in the world.
2.8L engines never have problems with sludge unless you don't change the oil on a regular basis. Do the work yourself, any maintenance isn't hard to do on an A4.

 

^lol seriously. i wonder what was running through the pennzoil guys minds. lets put wax in the oil to fill in the wear points...no need to worry about all the other places that wax is going to deposit itself

stick with amsoil. you can't go wrong with them. and the ONLY reason a 1.8t is going to sludge is poor maintenance. granted the pick up tube design could be improved, but as long as you keep fresh oil in there, it wont ever sludge. and that is true with ANY engine.

 

pennzoil aside- oil is supposed to turn black. people always think that when its black its dirty and needs a change. oil collects carbon deposits and other junk from the engine and contains that stuff within the oil.

it burns off hydrocarbons and condensation when it gets up to operating temperature, which is why adding an oil cooler that is too big is a bad thing, if the oil never gets up to a certain temp., it doesnt have a chance to burn all that crap off and gets dirty much faster. not to mention all the other stuff (fuel, water, coolant) that can get into the oil thins it out and reduces the anti-friction properties.

change your oil at recomended intervals regardless the color (unless you specificly want to flush something out). when it gets darker that just means its doing its job. although if your engine is perfectly clean and working, it wont get black as quickly.

 

^ yeah! what he said lol!
but seriuosly...