Expert answer

Hi Mark,

The government knows the emissions of each vehicle simply because each vehicle is put through a series of official laboratory tests as part of the process of homologation — the legal process whereby a car is pronounced as passed for sale to the public - and that data is made available by the car manufacturers. As for which is cheaper to tax, it’s down to the CO₂ emissions and we’d have to know which make and models you’re looking at before we could give you a precise answer, but in most cases, for a given car, the diesel would have lower CO₂ emissions and hence motor tax.

Expert answer

Hi Gino,

That Ford 1.6 TDCi diesel engine is one of the most common engines around, as it has also been used by Mazda, Volvo, Peugeot, Citroen and MINI. It has one major vulnerable spot and that is that sooty, gummy deposits can build up in areas that are supposed to be kept cool and lubricated by oil. If the deposits build up enough, they can block the oil passage and cause component failure — most commonly of the turbocharger. The best way to prevent that happening is with regular servicing (at least once a year depending on mileage) and making sure that you always use a high-quality grade of synthetic oil for the engine.

The 1.6 petrol engine, the 100hp version, is a much simpler unit and it’s pretty reliable, mostly because it’s a much older design. It won’t be as economical nor as punchy in its performance as the diesel, but if it’s reliability you’re looking for, it might be the better option. 

Expert answer

Hi Kevin,

It would have been useful to have more details about the car, such as age and engine, as it varies considerably. I'll deal with the 2013 on model, which is still in production.

All 1.2-litre petrol engines:
 - up to Sep 2014, 180,000km/10 years
- Oct 2014 to Apr 2017, 175,000km/10 years
- from then on, 100,000km/6 years first, then every 200,000km/12 years

1.5-litre BlueHDi diesel: every 180,000km or 10 years

All 1.6-litre diesel engines: 175,000km or 10 years

All 1.6-litre THP petrol engines: timing chain

1.6-litre VTi petrol engine: 150,000km or 10 years

All 2.0-litre diesel engines: every 180,000km or 10 years

Expert answer

Hi Donal,

Well, fuel consumption depends very much on your own driving style and where (and to an extent when) you do most of your driving. That said, in general, we wouldn’t expect that 1.0 TSI engine to be much thirstier overall than the 1.6 diesel. In our tests, both engines are in and around as economical as each other and you should expect to get around 50mpg from either with a light foot. The diesel may be a little better than the petrol option at a sustained high-speed cruise. However, with such low annual mileage, we suspect that the petrol engine will cost less to maintain in the long run. It's probably the best option for you.

Expert answer

Hi Nigel,

We know of an issue with the clutch assembly that causes what sounds like engine noise in the naturally aspirated 1.0-litre Polo engine. In the 1.0 TSI models, apparently a fault with the engine control unit (ECU) can cause whining from the engine as well. Neither of those sound like the problem you have, though.

Expert answer

Hi Tony,

The second-generation Octavia launched in 2004, which means you're most likely looking at two completely different generations of the model. There will be some small number of parts potentially shared across both, but not a lot at all, especially as the engines are also different.

Expert answer

Hi Pat,

We certainly have noticed this trait in all Volkswagen Group DSG-based gearboxes (that's what the S tronic transmission is) and their attendant engines of late. The only explanation seems to be that VW’s various brands have trimmed back both engine power and responsiveness at low speeds, and especially at idle or when waking up from a stop-start cycle, in order to optimise their figures in the new WLTP emissions and economy tests. VW is certainly not the only one to do this, but it does seem to be more obvious with VW Group models than with some other manufacturers. Shifting the gearbox into Sport helps a bit, but it’s not a total fix.

One cure might be a total vehicle upgrade — we’ve noticed that the new ‘Evo’ versions of the 1.5 TSI petrol and 2.0 TDI diesel engines are noticeably less sleepy. Or, alternatively, trade in for a version with a manual gearbox — that is the simplest cure of all.

Expert answer

Hi Leigh,

It depends on the engine. There's a timing chain in the 1.6, 1.8, 2.0 and 2.4-litre petrol engines and a timing belt in the 2.0-litre diesels. The 2.2 diesel, which only went into production in 2005, has a timing chain.

Expert answer

Hi John,

That's kinda a 'how long is a piece of string?' question, as no two engines are created equally. I mean, every different 1.6-litre diesel engine has a different realistic life span. And while it's reasonable to presume that a diesel engine is designed to be driven over higher mileage, I don't believe that manufacturers aim for 'worse' durability for their smaller petrol engines. 

Expert answer

Hi John,

All engines fitted to the 131-generation Toyota Avensis used a timing chain, not a belt.