Castrol has an on line oil checker

Correct oil for your car is 10w-40, semi synthetic. I would go for the Mobil Super 2000.

Go on Castrol website, type in your Reg. No. and they will recommend the oil, easy.

personally I would not use any additive. oil companies invest millions, why dilute with an unknown snake oil which may or may not work (anyone ever independently evaluated?)

If you use the correct type of oil, buy the best you can afford and are not doing any type of 'extreme' driving, such as racing or off road, then you should not need to add any type of oil additive. Engine oils contain their own additives and conditioners which should give engines the protection they need, as long as manufacturers' servicing intervals are followed.

The below is my opinion only!
I would not use Slick 50! It contains PTFE which is a solid. It's basically the same stuff that is used to coat non stick pans. PTFE has it's benefits but not in engines! It can eventually break down and cause blockages in oil ways and filters. NASA's research lab conducted their own test into this type of additive and concluded it can be detrimental to an engine. Don't just take my word for it, Google 'Slick 50 tests' and get all the facts.

I have personally used Extralube ZX1 Micro Oil Treatment previously in a few of my cars. It contains no solids and has been independently tested by laboratories and race teams around the world and also carries a NATO stock number. I noticed it made a difference to the noise and running of the engine (much quieter and smoother).

Both Slick 50 and Extralube ZX1 Micro Oil Treatment are available from Halfords.

have passat tdi 1999 110 bhp which is not require fully syntetic so partly systetic should be fine. Requirement only 10W30 to 15W50.

Castrol Magnatec 10w-40 A3/B4 is from the updated Castrol Magnatec range, equally suitable for petrol and diesel engines and replacing the separate Magnatec 10w-40 A3/B3 and Magnatec Diesel B3 engine oils

Not much. It all depends on your engine's requirements. The A3/B3 signifies the performance category of the oil.

A = Petrol, B = Diesel and C = Catalyst compatible or low SAPS (Sulphated Ash, Phosphorus and Sulphur).

They are split as follows:
A1 Fuel economy petrol
A2 Standard performance level (now obsolete)
A3 High performance and/or extended drain
A4 Reserved for future use in certain direct injection engines
A5 Combines A1 fuel economy with A3 performance

B1 Fuel economy diesel
B2 Standard performance level (now obsolete)
B3 High performance and/or extended drain
B4 For direct injection car diesel engines
B5 Combines B1 fuel economy with B3/B4 performance

C1-04 Petrol and Light duty Diesel engines, based on A5/B5-04 low SAPS, two way catalyst compatible.
C2-04 Petrol and light duty Diesel engines, based on A5/B5-04 mid SAPS, two way catalyst compatible.
C3-04 Petrol and light duty Diesel engines, based on A5/B5-04 mid SAPS, two way catalyst compatible, Higher performance levels due to higher HTHS.

Hope that helps.

castrol has an on line oil checker

Petrol or diesel? Engine size?

castrol has an on line oil checker

Hi, thanks for your interest in Castrol Magnatec 10W40 A3 B4 Oil 4 Litre. This would be the correct product for your vehicle.