What Car? Q&A - What does FSI, TDI and DSG mean?

Q: I am considering buying a Skoda Octavia, but am confused by the different terminologies, with FSI, TDI, Tiptronic and DSG all appearing in the brochure. I'm looking for fuel economy over performance, so which of these are best for me?
Bernadette Santiago

A: FSI and TDI are both direct-injection fuel systems - the former applies to petrol engines, the latter to diesels. Direct-injection fuel systems offer more power, better fuel economy and lower emissions. Diesel - badged TDI in Skodas - remains king in terms of frugality, although the FSI petrol models aren't far behind. The other two are both gearbox options and are a little more confusing.

DSG (Direct Shift Gearbox) is a manual gearbox with two automated clutches, allowing quick and efficient gearchanges. As you select one gear, the next is primed to cut in as soon as you nudge a gearlever or tap a paddle behind the steering wheel.

Such gearboxes are particularly smooth in operation and very efficient - in some cases, fuel economy and carbon dioxide emissions figures are better than manual versions. There's also a fully automatic programme, but it's not entirely jolt-free.

Tiptronic is a conventional automatic gearbox with the option to manually control the gears. Unlike DSG, it slightly increases fuel consumption but offers smoother gear changes.

For a full run-down of all this and similar terminology, check out our glossary by clicking here.