HYDRA EHN-99: Cetane Booster

Our Price:  £21.50(Inc. 20% VAT)(£17.92 Exc. VAT)
Pack Size:

  (8 Reviews)
  • 99% Pure 2-EHN 2 Ethylhexyl Nitrate cetane improver 4 to 8 points.
  • Improves performance and economy whilst reducing harmful engine emissions.
  • Reduced engine knock with smoother running and better pickup.
  • Cetane Booster for diesel, red diesel, biodiesel diesel, ULSD, MGO etc.
  • 50ml Treats Up To 50 litres of fuel.

Brand:  HYDRA



  • A 99% pure 2-EHN (2 Ethylhexyl Nitrate) cetane booster
  • Can be used in all diesel types e.g. diesel, red diesel, ULSD, MGO etc.
  • Boosts the cetane number of your vehicle by 4 to 8 points
  • See improved performance and fuel economy with a reduction in harmful emissions
  • EHN-99 reduces engine knock for smoother running and better pickup



Using Hydra EHN-99 is simple and can be used in all grades of diesel fuel. Next time you’re refuelling, make sure your tank is at least 10% full and then add the correct dosage to your tank before filling up as usual. Can also be added after refuelling.

The required dosage is between 1:1000 and 1:500, depending on the quality of fuel and level of performance increase desired.

Low Dose Rate 1:1000 – Add 1ml of Hydra EHN-99 to every litre of fuel

High Dose Rate 1:500 – Add 1ml of Hydra EHN-99 to every 500ml of fuel



The quality of diesel fuel is determined by a number of factors, these include it’s viscosity, what is pour flow point is, how resistant it is to contaminants such as bacteria. But arguably the biggest factor determining a fuels quality is it's cetane number.

The Cetane number is a measure of the combustion quality of diesel fuel, a diesel fuel with a low cetane rating has poor combustion quality and will result in rough engine operation, such as excess engine noise/vibration, reduced cold start ability and increased emissions/ soot build up.

However, a higher cetane fuel that is a proper match for the engine will reduce the ignition delay, liberate BTU energy form the fuel and drastically improve performance and fuel economy, making for a smoother, quieter drive overall.

Standard European forecourt diesel usually has a cetane number of around 51, with premium diesel a little higher. Depending on the engine design, however the optimum cetane number for most vehicles is in the high 50s low 60s.

Matching cetane number to an engine is essential in maximising your vehicles performance, biodiesel fuels in particular have a much lower cetane rating so treating these fuels is heavily recommended.

Hydra EHN-99 serves to provide an economic route for individuals to create high cetane fuels themselves, saving money over forecourt premium diesel.



Alkyl nitrates offer by far the greatest improvement in cetane number over other additives.

With measured cetane increases of up to 8 points. 2-EHN is the most popular and well respected of the Alkyl nitrates in the industry, creating more consistent ignition quality whilst reducing negative combustion qualities.



Many fuel additives on the market contain high amounts of useless filler, with manufacturers insisting on one bottle per tank. For example, some 200-300ml bottles meant to treat a single tank of fuel have as little as 20% active ingredients.

This is lucrative for the manufacturer, but terrible value for the consumer, so it is important to understand what you should be getting for your money.

The optimum amount of 2-EHN is around 30-100ml per 50 liters of fuel (depending on the engine requirements and base cetane level of the fuel) so to ensure you are getting the best value make sure the product is at least 50% 2-EHN

Hydra EHN-99 is 99% pure 2-Ethyllhexyl nitrate making it by far the best value diesel additive, EHN-99 contains no unnecessary filler with 100% active ingredients ensuring that your fuel receives the maximum cetane boost possible, giving you a better fuel burn, smoother engine and higher mpg.



All of our products are manufactured to the highest specifications at our UK plant, which is accredited to ISO 9001:2015, ISO 14001:2015 and ISO 45001:2018.


Add to fuel tank then top up with new fuel. Fuel tanks being treated should be at least 10% full. Usual dose at 1:1000 to 1:500 depending on the quality of fuel and performance increase required. Can be used in all grades of diesel fuel including biodiesel fuels.

Dose Rate 1:500. Add 1ml Hydra EHN-99 to 0.5 litres of fuel.

Dose Rate 1:1,000. Add 1ml Hydra EHN-99 to 1 litre of fuel.

What is the best diesel cetane booster?

Alkyl nitrates give the greatest increase in cetane number, which they will increase by up to 8 points with measured increases of up to eight points.  The most used and most cost-effective alkyl nitrate is 2-EHN (2-ethylhexyl nitrate). It gives exceptionally good ignition reduction times whilst reducing harmful emissions.

Is cetane good for diesel?

All diesel engines require a minimum cetane number to operate at their most efficiency. Often cheap supermarket fuels have only the minimum cetane number to meet EU diesel fuel specifications. By increasing the cetane number you decrease the ignition delay giving better combustion and fuel efficiency

Is too much cetane bad?

The cetane number will only increase by a maximum of 8 points, and the increase will depend on the starting point number of your fuel. Therefore, if your cetane number is high to start with adding a lot more cetane will not make any difference. So, it is important to know what your current fuels cetane number is. If you do not know the number, then to save the maximum amount of money it is always a good idea to use a cheap supermarket fuel as your starting point.

How do you increase cetane number of diesel fuel?

Simply by adding 2-EHN, the higher the starting number the higher the concentration of cetane booster already in the fuel. It costs the refineries money to add cetane therefore generally speaking the cheaper the diesel fuels the lower the concentration of cetane already in the fuel.

Average Rating (8 Reviews):  
Write a Review and share your opinions!

Best product for your diesel
09 January 2022  | 

I've been using this for over 10 years . It makes normal fuel into super fuel. Add 1ml to 1 litre of fuel for the correct ratio. You'll be delighted at just how quiet your diesel car becomes after a few doses of ehn99. It increases cetane by upto 4 points for more power and diesel burns at a much cleaner rate ,which is good for your egr, dpf ,inlet manifold,exhaust manifold,swirl flaps . Soot kills diesels as it also enters the engine oil. With ehn99 you are reducing soot levels ,try using just a litre bottle for a few weeks ,when you realise it's potential you'll be ordering the 5 litre can like I do.

Was this helpful to you?  Yes  /  No

9 of 9 people found this review helpful.

Ive been using this for ages
15 September 2020  | 

Amazing product. I add 100ml to 50L fuel and find this mix gives me best results for MPG and power. Hydra Cetane Booster works out to be very cost effective in use - I will keep using it

Was this helpful to you?  Yes  /  No

3 of 3 people found this review helpful.

More energy
16 October 2018  | 

After adding Hydra Cetane Booster to my VW Passat my garage used their diagnostic tester and found vastly improved results. My car has more energy and certainly keeps my DPF clean. Will keep using it and another benefit - its not expensive to use

Was this helpful to you?  Yes  /  No

8 of 8 people found this review helpful.

Fantastic product for my car
27 August 2018  | 

After using this Cetane Booster I thought my car had turned into a Ferrari sports car! This product is brilliant and my fuel gauge hardly moved. Will buy again as it works out cheaper than other additives with better results.

Was this helpful to you?  Yes  /  No

8 of 8 people found this review helpful.

Just read what I have to say about this product
24 May 2018  | 

Tried and tested. I found the more I used this Cetane Booster the greater the improvement. My Kia now runs smoother and quieter. I add this to every fill and I can heartily recommend this product.

Was this helpful to you?  Yes  /  No

7 of 7 people found this review helpful.

Better mpg with incredable smooth running
19 March 2018  | 

My Renault was juddering badly when I accelerated so I thought I would try this product. I was amazed as the juddering stopped and my car is now running smoothly. Also after adding 100 ml to the tank my MPG has vastly improved.

Was this helpful to you?  Yes  /  No

7 of 7 people found this review helpful.

Yes this product does work!
22 October 2017  | 

Reluctant to try at first but as I had cold knocking on my van bought some to try. It worked and the knocking stopped. I now use it on all my vehicles and find the MPG has significantly increased.

Was this helpful to you?  Yes  /  No

8 of 8 people found this review helpful.

Best Additive Around
04 May 2017  | 

A friend who runs a garage put me onto this product and I am pleased she did as my car is performing so much better now. So much better than other well known additives !

Was this helpful to you?  Yes  /  No

7 of 7 people found this review helpful.

Related Products
HYDRA CEBO: Cetane Booster + Lubricants
HYDRA CEBO: Cetane Booster + Lubricants
From:  £17.99

Contains the best Cetane Booster (2-Ethyl Hexyl Nitrate) + Lubricants

HYDRA CEBO: Cetane Booster + Lubricants
HYDRA CEBO: Cetane Booster + Lubricants
From:  £17.99

Contains the best Cetane Booster (2-Ethyl Hexyl Nitrate) + Lubricants

HYDRA DPB-100: Detergents + Lubricants + Cetane Booster
HYDRA DPB-100: Detergents + Lubricants + Cetane Booster
From:  £14.50

Reduces Fuel Consumption, Cleans Injectors, Pumps etc