I am sorry to hear of your turbo charged VW motor. I am assuming that you have the 1.8t motor in Passat wagon. Don't beat yourself up, the motor should be run over the long haul with a full synthetic motor oil, but many that have run the full synthetic 5W40 motor oil have found themselves in the same boat. I am not sure how tech savy you might be regarding maintenance on a turbo charged motor, but if a lot of what I have to say is already known then forgive me.
A turbo charger is placed in the exhaust system to use the hot exhaust to spin a minnie turbine to force air back into the intake of the motor to create more performance out of a small motor. Yes the flow of exhaust gases is free to propel this air flow. But exhaust gases are very hot, especially when it is placed in close proximity to a catalytic convertor to burn off any unburned fuel before exiting the tailpipe in the form of emissions. The downside of this is that oil must be circulated to the turbo unit in a severe high heat environment to lubricate the turbo bearings as well as cool the unit. There are a few things that you can do to help prevent the high turbo unit heat from cooking the motor oil. The biggest one is letting the motor idle for a minute or two before shutting off the motor, especially after a long run. This allows the turbo unit to cool down some before the oil circulation comes to rest. Most folks think of oil as a lubricant, which it is. But most folks don't think of oil as a coolant. Motor oil carries heat away from hot spots in the motor. These areas would include high friction areas such as cam lobes and valve lifters as well as crankshaft bearings and piston rings sliding against the cylinder walls. But in your situation the highest heat is at the turbo unit.
The turbo bearings in particular are problematic in this turbo assisted motor. Oxidized oil deposits get rolled up and discharged into the oil flow stream exiting the turbo unit downstream to the oil pan. Unfortunately these rolled up balls of oxidized oil are of a particular size that are large enough to plug the oil pick up screen. Think of it as some one throwing a tennis ball at a cyclone fence. The ball lodges into the mesh pattern of the fence. The same phenomenon occurs with these little balls of sludge hitting the oil pick up screen. And over time enough of those that get stuck in the screen reduce the ability of the oil pump to suck oil out of the oil pan and provide proper oil flow.
With respect to using Auto-Rx to solve the issue by dissolving sludge, or cleaning the pick up screen, there has to be adequate oil flow in the motor. So a totally blinded or plugged pick up screen is a senario where Auto-Rx is not going to be adequate. Auto-Rx can only clean where oil is free to flow in the oiling system. However if the oil pick up screen is only minimally blinded then Auto-Rx would provide good results. Often times the dash board warning light to stop operation is due to the oil sending unit sensor being dirty or sludged up. That is whereby the sensor is no longer able to read what the oil pressure or flow is. Then a warning on the dash board will occur, even though oil is circulating properly. The oil sending unit sensor is located directly above the oil filter housing assembly on most motors. It is a question of whether or not the dash board warning is real or just a sensor giving the central computer a false read. A decent/trusted mechanic should be able to put a mechanical oil pressure guage in place, in the shop, for the purpose of identifying whether oil is circulating with proper pressure to tell you whether or not you can operate this motor safely, without catastrophic failure.
If the oil pressure and flow is not sufficient to operate the motor, then the best advise would be to have the oil pan dropped and have the oil pick up screen either cleaned or replaced, as well as the associated tubing. Or to save money you could have a mechanic take out the oil sending unit and clean or replace, which is a small effort to see whether or not an oil pan drop is necessary.
As you have read, likely, Auto-Rx is a very methodical cleaner. And by that I mean, it works fastest in areas of the motor with higher heat developed from from friction and heat. These are the areas of the motor design whereby oil flow is directed. So the difference between Auto-Rx and a solvent flush is quite simple. Auto-Rx will work first on the key working components of the motor, relatively slowly dissolving deposits in a systematic fashion protecting the key parts. Whereas with a solvent flush, sure the oxidized oil deposits or sludge will be removed, but more than likely in chunks, rather than slowly dissolved. This could add insult to injury with respect to a partially plugged oil pick up screen.
So what I would recommend would be the following. If you have a trusted mechanic, have them check the oil pressure with a mechanical guage to see if you are getting a true read on oil pressure and flow. And if so then I would proceed with an Auto-Rx cleansing for sludge right away. For your motor I would have an oil change done with Shell Rotella T6 in the 5W40 spec and a new oil filter installed. As part of the oil fill include 2 bottles of Auto-Rx Plus. And then drive the car normally for 1500 miles. At which time have the oil filter only replaced at the 1500 mile mark. I say this as a safe guard as there may be a tremendous amount of sludge dissolved that may clog up the oil filter.
If a trusted mechanic tells you you should not drive the motor, then you will have to pay to have the oil pan lowered and the pick up screen cleaned or replaced, which is somewhat labor intensive. And then you will want to start an Auto-Rx application to slowly dissolve the mass of oxidized oil deposits in the motor.
I hope this information is helpful to you in determining a path of action on your Passat Wagon. Should you have further questions, please reply.
