B0 or B7 diesel – which fuel should you put in your car?

In most cars you simply put in B7 and that is fine – provided your engine’s manufacturer allows it. B0 is pure diesel with no biocomponents: it copes better with frost and long storage, but it is more expensive and harder to get. The B0 versus B7 difference comes down to one thing: B7 has up to 7% of a bio-additive (FAME), and B0 has none. It seems like a detail, but it really affects how the fuel behaves in winter, how long you can keep it in the tank and how quickly the injection system gets dirty.

B7 or B0 diesel – what is it actually about?

The letter "B" in both designations refers to biodiesel (FAME) – esters produced from vegetable oils or animal fats, which are blended with classic diesel made from crude oil. The number after the letter says how much of this biocomponent there is in the fuel at most. B7 is up to 7% FAME, and B0 is zero – pure diesel from crude oil alone.

The fact that you almost always fill up with B7 at the station is no accident. Fuel producers are obliged by law (the National Indicative Target) to place a set share of biocomponents on the market, and they meet that obligation precisely through the widespread sale of B7. That is why, behind the innocent-looking name "diesel" on the pump, there is almost always B7 – the designation tends to be tucked away somewhere at the side, in smaller type.

A curiosity that explains a lot: every fuel with a biocomponent is based on pure B0 anyway – the FAME is only added at the end, at the terminal during loading. So B0 is nothing exotic, just the same diesel, only without the last step. We write more about B0 itself on our blog, and we break down the basics of diesel designations in the piece on the types of diesel fuel: B7, B10, XTL.

B7 diesel – characteristics, advantages and drawbacks

B7 is the market standard – the fuel you will find at every station in Poland and which complies with the PN-EN 590 standard and with the requirements of the vast majority of modern diesels. For the everyday driver it is the default choice and, in 99% of cases, completely safe.

The advantages of B7:

• availability – it is literally everywhere, you do not have to look for anything,
• a lower price than B0 and premium fuels,
• compliance with the standards and with the recommendations of modern engine manufacturers,
• a smaller environmental footprint thanks to the share of renewable component.

The drawbacks of B7 (mainly when standing for a long time):

• the FAME biocomponent absorbs water from the air more readily, which encourages corrosion and the growth of microorganisms in the tank,
• it ages (oxidises) faster during longer storage,
• it copes worse with a hard frost than pure B0,
• in longer storage it forms deposits and lacquers on the injectors more readily.

These drawbacks barely affect a car that is driven every day – the fuel does not have time to age, because you burn through it quickly. The problem only starts with cars and machines that stand for weeks. We say more about why diesel itself can "take apart" an engine from the inside in the analysis of why a modern diesel breaks down by itself.

B0 diesel – characteristics, advantages and drawbacks

B0 is pure diesel without a gram of biocomponent – exactly what we all used to fill up with before 2009, before EU regulations introduced the mandatory FAME addition. It is sometimes called "zero-grade". It also differs visually: B7 is cloudier and has a yellowish tint, B0 is clear, almost transparent.

The advantages of B0:

• better frost resistance – it proves itself in a hard winter and with reliable starting,
• greater stability during long storage (there is no FAME to "go sour" first),
• less tendency to bind water, and therefore a lower risk of corrosion in the tank,
• often pointed to as gentler on sensitive, older pumps and injectors.

The drawbacks of B0:

• poor availability – it appears at the big stations irregularly, you will more often come across it at wholesalers and at small, private stations,
• usually more expensive than B7,
• the price can be unstable, because it is a niche product,
• for a driver covering a high, everyday mileage the real benefit is small.

The difference between B0 and B7 – a comparison table

So as not to drown in descriptions, we have gathered the most important properties of both fuels in one place.

Criterion	B7 diesel	B0 diesel
FAME biocomponent content	up to 7%	0% (pure crude oil)
Availability	at every station	niche, you have to look for it
Price	lower, standard	usually higher by approx. €0.04–0.12 per litre
Frost resistance	weaker	better
Stability in storage	shorter (FAME ages faster)	longer
Tendency to bind water	greater	smaller
Environmental impact	more favourable (renewable component)	less environmentally friendly
Recommended for	everyday cars, modern diesels	little-used cars, long fuel storage, older engines

As you can see, whether B0 fuel is better than B7 – that depends on how you use the car. For some, "zero-grade" is a real advantage; for others it is an unnecessary expense and a trek around the area looking for a station.

B0 and B7 fuel – how do they affect the engine and the injection system?

In a modern diesel, which is designed for fuel with a biocomponent, B7 is a safe choice and causes no problems. The biocomponent does, however, have two properties worth knowing about. First, FAME acts slightly like a solvent and over time can affect older rubber components and fuel system seals. Second – and this matters more – it attracts moisture, and water in the system is a straight road to corrosion of the pump and the injectors.

B0 does not have these "side effects", because it contains no esters. That is why it is sometimes pointed to for older units with sensitive, mechanical injection pumps and wherever maximum cleanliness of the system matters. It is not that B7 "destroys" the engine – in everyday use it is entirely safe – but with long periods of standing and sensitive equipment the difference starts to become noticeable.

If you are battling with water in a diesel’s fuel system or want to know how to get it out, we have a separate, practical guide on that – and when it comes to protecting the system itself, a regular diesel additive helps. Here it is worth reaching for TEC 2000 Diesel System Cleaner, which binds water and helps keep the injectors clean.

B0 vs B7 diesel and fuel storage

This is the moment when the difference between the fuels stops being theoretical. Diesel is not an "eternal" product – the FAME biocomponent begins to oxidise from the moment it is blended with the fuel base at the refinery, and the process continues throughout storage: in the tanker, in the tank at the station and in the car’s tank. The longer the fuel with FAME waits to be burned, the more acids, gums and deposits form in it, which can block the filter and settle on the injectors. That is why B0, as a fuel without FAME, naturally copes better with long storage.

The problem is that day to day you most often have B7 in the tank anyway – because that is what is at the stations. And here is the good news: the storage stability of B7 can genuinely be improved with the right additive. The ORLEN laboratory checked this.

Proof from the ORLEN laboratory. At the manufacturer’s request, ORLEN Laboratorium S.A. used the Rancimat method (the PN-EN 15751 standard) to test two samples of the same diesel – without the additive and with TEC 2000 Diesel System Cleaner added. The result speaks for itself.

Sample	Oxidation stability (Rancimat, 110°C)	PN-EN 590 requirement	Assessment
Diesel without the additive	65.09 h	min. 20.0 h	meets the standard
Diesel with TEC 2000	111.94 h	min. 20.0 h	+72%, more than 5× above the minimum

The induction period, that is, the fuel’s "freshness reserve", rose from 65.1 to almost 112 hours. It is an accelerated test at 110°C – in a real tank, at ambient temperature, such an advantage translates into many additional months of safe storage. How our preparations compare against ordinary fuel stabilisers, we show here.

⚠ IMPORTANT – is the fuel standing for longer? Protect it before it ages

If you are keeping diesel in the tank of a seasonal car, in a drum, in a generator set or in a storage tank for weeks or months – regardless of whether it is B7 or B0 – add a fuel additive as soon as you fill up for storage. It slows oxidation, limits the formation of brown deposits on the filters and helps keep the injection system clean throughout the storage period.

A proven choice here is TEC 2000 Diesel System Cleaner – the same preparation whose effectiveness was confirmed by the ORLEN Laboratorium study above.

B0 versus B7 price – what is the difference really?

B0 is usually more expensive than B7, but the difference can be surprisingly small. Depending on the station, the region and the current market situation, the premium for "zero-grade" is most often in the order of a few to several cents per litre. There are places where the difference is minimal, and there are places where it reaches around €0.12.

Where does this premium come from? The reason is regulatory and market-driven, not one of quality. By selling fuel without FAME, the distributor does not meet the mandatory biocomponent target (the NCW), so it treats B0 as a niche product, outside the main sales volume. Add to that the smaller scale and limited availability, which in itself pushes the price up.

When working out whether B0 pays off, it is worth taking into account more than just the price at the pump.

• The higher calorific value and potentially slightly lower consumption of B0 on long routes.
• Less frequent fuel filter changes with long-term use.
• The cost of the journey and the time spent simply finding a station with B0.
• The fact that with everyday, intensive driving the fuel will not have time to age anyway – so the advantage of B0 melts away in practice.

The price conclusion: for a driver with a high, regular mileage the premium for B0 usually does not pay for itself. The real economic sense of B0 appears with little-used cars, seasonal equipment and a hard winter.

Which diesel is better – B0 or B7? What to choose

There is no single right answer, because "better" depends on how and what you drive. There is, however, one overriding rule, more important than all the comparisons of properties and prices.

⚠ IMPORTANT – first check what your car’s manufacturer allows

Before you even start weighing up B0 versus B7, look in the owner’s manual and at the fuel filler flap. It is the engine manufacturer that determines what fuel it may be run on. If it allows B7 – you have a free hand: you can fill up with both B7 and the "cleaner" B0, and go by price, availability and the way you use the car.

This manufacturer’s recommendation matters more than any opinions from forums. Filling up with fuel against the specification is a risk that no saving on price makes up for.

When and who should choose B7 diesel

B7 is the sensible, default choice if:

• you drive the car every day and cover substantial, regular mileages,
• you have a modern diesel designed for fuel with a biocomponent,
• you care about convenience and a lower price, not about hunting for niche stations,
• your tank rarely stands full for weeks – you turn the fuel over regularly.

This group covers the vast majority of drivers. If that is you – stop wondering and fill up as normal. The one potential drawback of B7, namely ageing during long periods of standing, you neutralise with a fuel additive if you need to.

When and who should choose B0 diesel

It is worth looking around for B0 if:

• the car, the machine or the generator set stands unused for longer and the fuel has to survive in the tank,
• you are preparing for a hard winter and care about reliable starting in a severe frost,
• you have an older diesel with a sensitive, mechanical pump and injectors,
• you drive a classic vehicle from the days when there were no biocomponents in fuel,
• you use agricultural or transport equipment, where reliability and storing fuel in reserve matter.

In these situations the advantage of "zero-grade" – frost resistance and better stability in storage – genuinely comes in useful. You just have to reckon with the fact that B0 first has to be found (quickest through apps and station maps, or a phone call to a wholesaler) and that you will pay a little more. If you happen to have no access to B0 and the fuel is going to stand in the tank, the solution is the diesel additive TEC 2000 Diesel System Cleaner, which also protects standard B7.

One last sentence worth remembering: what matters most is not whether you put in B0 or B7, but that it is a fuel approved by the manufacturer and – if it is going to stand for longer – properly protected. The rest you fine-tune to the way you drive.

FAQ

What is the difference between B7 and B0 fuel?

B7 contains up to 7% of the FAME biocomponent, and B0 contains none at all – it is pure diesel from crude oil. In practice B7 is cheaper and available everywhere, while B0 copes better with frost and long storage, but it is more expensive and harder to buy.

Which diesel is better – B0 or B7?

There is no single winner. For everyday, intensive driving in a modern car, B7 tends to be better. For little-used cars, seasonal equipment and a hard winter, B0 is more advantageous. What decides is the way you use the car and – above all – the engine manufacturer’s recommendation.

Is B0 fuel better than B7?

In terms of frost resistance and stability in storage – yes. In terms of price and availability – no. For a driver with a high mileage the difference is small enough that the premium for B0 usually does not pay for itself.

What is the price difference between B0 and B7?

B0 is usually more expensive by a few to several cents per litre, although sometimes the difference is minimal. Prices change from day to day, though, so it is worth checking the current rates at the specific station.

Can you fill any diesel with B0?

First check the owner’s manual and the filler flap. Most engines that allow B7 will cope with B0 as well, but the manufacturer has the last word. If the specification indicates a particular fuel, stick to it.

Can I mix B0 with B7 in one tank?

Yes, both are diesels meeting the PN-EN 590 standard and they can be mixed with no risk to the fuel system. The blend will simply have an intermediate biocomponent content.

Why is B0 so hard to get?

Because the biofuels legislation steers almost the entire retail market towards B7. The big corporations meet the mandatory share of biocomponents precisely through the widespread sale of B7, so pure B0 reaches the offer more rarely – more often at wholesalers and at small, private stations.

How do you protect fuel against ageing during storage?

Add a fuel additive as soon as you fill up for storage. It slows oxidation and limits the formation of deposits. The effectiveness of TEC 2000 Diesel System Cleaner in this respect was confirmed by the ORLEN Laboratorium study – the fuel’s stability rose by 72%.