Tips and Advice

What does TDI stand for?

The letters ‘TDI’ are used on VW Group diesel engines but what does it stand for and what do other companies call their diesels?

Audi's latest engine labelling system continues to baffle, though. The 3.0-litre diesel is the 50 TDI – 55 TFSI the petrol.

Car brochures seem to be overflowing with acronyms for different features. There’s technology such as ABS (anti-lock braking system), ESP (electronic stability package, usually, otherwise known as traction control) and ACC (adaptive cruise control), and they’re just the generic ones. Most manufacturers have some of their own acronyms, just to confuse things further.

You’ll find that various acronyms are used when talking about engines too. Often this is because a car is available with more than one engine and it’s an easy way to tell the difference between them. Diesel, petrol and hybrid cars will all be called different things.

Should you buy a petrol or diesel car?

TDI engines

TDI is used on all current Volkswagen Group diesel engines, so you’ll see those three letters if you’re interested in new or used diesel Audi, Volkswagen, SEAT, Skoda, Porsche or Bentley models.

You might think the ‘D’ in TDI stands for ‘diesel’, but in fact the acronym is short for ‘Turbocharged Direct Injection’. Turbocharging is used to boost power but allows the engine to be a smaller size, helping to save fuel. The smaller engine also means lower weight (which brings benefits to economy, acceleration and handling) and more space for crash protection and interior occupants. Direct injection improves the fuel combustion cycle, leading to higher torque and lower exhaust emissions.

TDI vs TSI

While TDI is VW’s shorthand for its turbo diesel engines, the letters ‘TSI’ are used on its petrol engines. This stands for ‘Turbocharged Stratified Injection’ and, again, the use of a turbocharger reduces fuel consumption, emissions and engine size, while making more power and enabling access to it lower down the rev range.

If you’re looking on the used market, a VW Group petrol engine may be badged ‘TFSI’ with the ‘F’ standing for ‘Fuel’. These are very similar, but the TSI engines tend to be newer and come with a few improvements over the TFSI engines, such as a redesigned fuelling system, upgraded engine management systems and a move to chain timing from belt timing.

TDCi, CRDi, dCi and other diesel engines

As mentioned above, TDI is used on VW Group diesel engines, but other companies use different acronyms for their diesels. As a general rule, diesel engines will have a ‘D’ in the acronym. The GDi engines Kia and Hyundai use slightly confuse things - these are petrol engines.

Diesel engine names explained:

Alfa Romeo - JTDm (uni-Jet Turbo Diesel modificata)BMW - for diesels, the model designation is followed by a ‘d’ (i.e. 118d)Citroen, DS, Peugeot and Vauxhall - BlueHDi (ultra-efficient versions of High-pressure Direct injection engines)Fiat - MultijetFord - TDCi (Turbo Diesel Common-rail injection) for older models, EcoBlue for newer carsJaguar and Land Rover - ‘D’, then the engine’s horsepower in PS (i.e. D150)Honda - i-DTEC (Intelligent Diesel Technology Engine Control)Hyundai and Kia - CRDi (Common Rail Diesel injection)Jeep - Multijet or CRD (Common Rail Diesel)Mazda - SkyActiv-DMINI - ‘D’ badgeMercedes - CDI (Common-rail Diesel Injection), or the model designation followed by 'd' (i.e. CLA 220 d)Nissan, Renault and Dacia - dCi (direct Common-rail injection)Toyota - ‘D’ badge on engine (D-4D models have four-wheel-drive)Vauxhall - older models have CDTi engines (Common-rail Diesel Turbo injection)Volvo - ‘D’ then model designation (i.e. D5), or ‘B’ then model designation for mild-hybrid engines (i.e. B5)

Read our guide to the best diesel cars to buy this year, or see what you need to know about adding AdBlue to diesel engines.

Recommended

Volkswagen introduces new Active trim level
VW T-Roc Cabriolet
News
19 Apr 2021

Volkswagen introduces new Active trim level

Volkswagen T-Cross SUV now available in Black Edition trim
Volkswagen T-Cross Black Edition
Volkswagen T-Cross SUV
9 Apr 2021

Volkswagen T-Cross SUV now available in Black Edition trim

New Volkswagen ID.4 trim levels join range
2021 Volkswagen ID.4 driving - front view
Volkswagen
8 Apr 2021

New Volkswagen ID.4 trim levels join range

New Volkswagen Taigo coupe-SUV on sale in UK in late 2021
Volkswagen Taigo sketch
Volkswagen
30 Mar 2021

New Volkswagen Taigo coupe-SUV on sale in UK in late 2021

Most Popular

Car dashboard warning lights: the complete guide
Car dashboard symbols and meanings
Tips and advice
13 Apr 2021

Car dashboard warning lights: the complete guide

Best new car deals 2021
Skoda Fabia
Deals
16 Apr 2021

Best new car deals 2021

2021 scrappage schemes: the complete guide
Scrappage schemes - Ford Focus
Tips and advice
20 Apr 2021

2021 scrappage schemes: the complete guide

Tips & advice

View All
Car dashboard warning lights: the complete guide
Car dashboard symbols and meanings
Tips and advice
13 Apr 2021

Car dashboard warning lights: the complete guide

Electric car charging stations: a complete guide
Tips and advice
10 Nov 2020

Electric car charging stations: a complete guide

PCP vs HP – what's the difference?
Tips and Advice
23 Mar 2020

PCP vs HP – what's the difference?

Average speed cameras: how do they work?
Average speed cameras: how do they work?
Tips and advice
24 Feb 2021

Average speed cameras: how do they work?

Best cars

View All
Best car interiors
Best cars
10 Mar 2020

Best car interiors

Best electric cars
Best cars
24 Dec 2020

Best electric cars

Best cheap-to-run cars
Toyota Prius front 3/4 cornering
Best cars
1 Feb 2021

Best cheap-to-run cars

The UK's top 10 fastest hot hatchbacks
Hot hatches
9 Apr 2020

The UK's top 10 fastest hot hatchbacks