What would be the best oil recommended for the 1.9 Tdi engine for the best performance and engine wear?

Darren —

First, have a butcher's at my thread about Haynes showing the wrong grades. This, along with the comments below, should steer you in the right direction. If you're still lost, post back with details of your car — specifically, engine swept volume, power output, year, fitment or otherwise of a particle trap.

Unit injector engines are very demanding when it comes to lubricant. Injection pressures are a lot higher than anything a common rail system can deliver, and this has implications for many aspects of the combustion process.

The 'standard' oil testing régimes used by the ACEA and the API do not cover unit injector engines, so the first thing you should look at are VW's own oil performance specifications.

Here is a rather hurried tour through the VW specification codes that apply to unit injector TDI engines.

505.01: This is high-quality oil, and it is expensive, but it is the bare minimum you should use in a PD TDI. Do not use any lower grade, even as top-up!

If you have an emergency and really have to use something without VW accreditation, insist on the ACEA's B4 grade. But I'm afraid my sympathy for anyone who can't be bothered to carry a litre of top-up is rather scant...

If the vehicle is is being run with variable service intervals, it needs grade 506.01.

The newest grade to be introduced by VW is 507.00. This covers all PD TDIs on all servicing régimes. It is essential that you use this grade if your car has a particle trap.

If you have an 'emergency' in a vehicle with a particle trap, the oil you use must have not only the ACEA's B4 rating but also a Cx rating, to indicate that it's compatible with after-treatment devices. C4 is the best of these grades, but in any event don't drop below C3. If you can't manage an oil with B and C grades, drain the oil and change it ASAP. But you'll probably have poisoned your cat anyway...

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Rotary pump TDIs

Here we're looking at the 90ps and 110ps four-cylinder motors, 115ps and 140ps five-cylinder engines, and the derated commercial versions of same.

This is dead easy. Don't worry about VW's in-house specs. Any ACEA B4 will be splendid. Beware of B3: one of the few differences between B3 and B4 relates to the VW TDI rotary pump engine. Don't drop below B3, even for top-up. The VW grade required for these engines was 505.00.

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ACEA 'E' specs

Ignore them. They apply to truck oils, and the requirements of an oil in commercial applications are completely different. For example, the base oil for a truck application must be very shear-resistant, but the resistance to acid attack will be nowhere near as good in a truck oil as it is in a lubricant designed for cars. Besides which, the E grades aren't actually progressive.

Sorry but that did confuse me a bit.

My octavia is a 1.9 Tdi 110 bhp 2001 model.

I don't think it has a particle trap.

I last used castrol gtd 10-40 grade, bearing in mind that i cover long journeys in the Rep of Ireland.

Simple.... Get what ever is says in your skoda owners manual.

The 110ps engine is a rotary pump engine, and you should use oil to ACEA B4 spec.

Owner's manuals are perforce produced at the same time as the car they come with. This means that as oil specs change and improve, the oil grades they specify can (and do) cease to exist. The result is that the owner's manual can tell you to use oil of a grade that's not referenced by any lubricant you can actually buy.

For that age of car I very much doubt it. And you will find that newer grades of oil will tell you what they are compatible with.

Stick with what the manual says, and you can't go wrong.