Talk:Fuel oil

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Undid addition of claim that a fuel oil is Transmix[edit]

Just like to clarify that although transmix can contain fuel oils, fuel oil is not transmix. Transmix refers to off-grade mixtures of gasoline and diesel fuels that are not usable or saleable as motor fuels and are therefore reblended to be refined again to within usable specs. ie: transmix is almost like junk oil. Fuel oil however, conforms to certain specifications for specific uses. Venny85 —Preceding comment was added at 14:59, 1 February 2008 (UTC)

Request addition of a missing class[edit]

Under Maritime, the table which displays bunker fuel grades, the author seems to have left out a pretty common grade too. A small addition is needed to it.

The table has 180cSt, 700cSt etc, but seems to have left out the 500cSt grade of bunker fuel. I'll see if I can get more detailed specs for this grade to add into the table, but if any of you guys already know, do feel free to edit it already.

Venny85 (talk) 06:04, 18 November 2007 (UTC)

fuel oil can be diesel fuel, heating oil, or biodiesel. —Preceding unsigned comment added by (talk) 06:59, 20 January 2008 (UTC) I was referring to marine fuel oils.

haha, actually i found out why already. Under ISO 8217, Specifications of marine fuels ISO 8217-96 edition, viscosities were specified at 100C. The viscosity at 100C of the RMH45 fuel oils would be about 500cSt at 50C, while the RMH55 would be about 700cSt at 50C. Under ISO8217-05 edition, viscosities are at 50C which also removed the 500cSt range and placed them as a 700cSt grade. Testing of kinematic viscosities of these products are done under the new ISO3104 or IP71 or ASTM D445 standards. Therefore, although the 500cSt isnt a standard grade, its still used as a specification for fuel oils in the range of 380cSt-500cSt. But, they will still be graded as 700cSt. Venny85 (talk)

Another question[edit]

Another question : What are the specifications of heating oil(s) ? Flash point, water and sediments,Kinematic viscosity, Sulfated Ash, etc. as an example of what I'm looking for: Nov 09 2006

Question: can someone from an oil major please fill some more details about the various supply chains and fuel oil transportation details please? Where does this stuff come from geographically? How does it get transported? And, how is it bought and sold? Are there trading markets? What types of deals are common? 21:35, 13 October 2005 (UTC)

what are the names of the six fuel oil grades,like #2 chemical    coposition is pentane,c5H12  — Preceding unsigned comment added by (talk) 16:06, 12 July 2012 (UTC) 

Expansion, corrections[edit]

The current article is correct as far as I can tell. Be careful when making changes to the "classes" part, as some otherwise reliable sources (government, industry) have incorrect information about fuel oil. One problem is that there are some many different names for the same thing, such as heating oil, No. 2 fuel oil, No. 2 distillate and No. 2 diesel fuel. Just as confusingly, there are a few things that people often say are the same thing, but technically aren't. For example, residual fuel oil is sometimes used as a synonym for No. 6 fuel oil. However, No. 5 is also a residual fuel oil, and No. 4 is often a mix of residual and distillate fuel oil. This mistake was made in the residual fuel article, which is actually about No. 6 fuel oil. I think the article should be merged into this one either rather than fixing it.

Additions - Andrew Waugh I added brief information about UK designations and other peripheral matter and would like to expand on the topic when time is available. I have plenty of info available as I'm a long serving (suffering?) equipment manufacturing company with 66 years historical / current data. end)

I've been trying to find information about the marine classes and I'll post it if I find any. It looks like they have some equivalencies with the fuel oils, but the specifications seem to be looser, such as allowing higher levels of sulfur. -- Kjkolb 04:36, 10 December 2005 (UTC)

I merged the articles. -- Kjkolb 09:50, 10 December 2005 (UTC)

Some information regarding the generic term for one of the lighter fuels Diesel Fuel Marine (DFM) would be useful. I'm still unsure as to whether that is a different name for Marine Diesel oil (MDO) or not. I work for MSC (Military Sealift Command) as a civilian mariner and all MSC and US Navy vessels use DFM for their main fuel (except nuclear vessels). However, the Navy is switching to MGO</a> because apparently it is cheaper(?). I thought that residual fuels were cheaper than lighter distillate fuels. Hengineer 10:44, 29 August 2006 (UTC)

Alterations - S. Ray i've just made some slight alterations to the article. Although not an expert in heavy fuel oils / residual fuel oils in particular i am a senior marine engineer on VLCC oil tankers with 30 years experience and felt my input may be useful. Firstly, with regard to the area of the article which stated that steamships are not used anymore; they are infact in use, and although the "glory days" of steam powered oil tankers may have passed, most if not all of the newer LNG and LPG carrying tankers are utilising steam power due to the fact that waste gas from the cargo tanks can be employed as a fuel. There are a huge amount of these ships being built therefore i feel it is factually incorrect to state that steamships are no longer used. I also made a slight extension to the early passage, which deals with the grading system and nomenclature of residual oils. Very few ships and people in the maritime industry, with the possible exception of some naval personnel, actually use this system. It is mainly reserved for those in shore side industral roles. Shipping tends to employ a simple system where critical aspects of the fuel are analysed and the suitability of the fuel is determined, mainly down to viscosity, flash point, pour point, sulphur and vanadium content etc. Please be aware that this is the first time i have used wikipedia for anything other than reading, and so if my actions and / or explanations are not fitting with common wikipedia practice i am happy to ammend them further. Also, if encyclopedic reference is required i can supply extensive detail from both ships and publications such as Lamb's Questions and answers on marine diesel engines, pounder's marine diesel engines, and various fuel oil specific books. If any further information regarding anything i have written or about the article in general i would be more than happy to expand on it or supply the information required. S. Ray, Chief Engineer.

Carbon chain length[edit]

A carbon chain length column was added to the table (not by me), but there are problems with determining them. Number 1 and 2 are pretty easy, although the numbers given vary a lot. Number 3 is so rare that I don't know if such information can be found. Number 4 and 5 are a problem because they are mixtures of residual fuel (number 6) and distillate (usually number 2), with number 5 having less distillate. There doesn't seem to be a fixed ratio of distillate and residual fuel. I think they just add distillate to batches of residual fuel, which vary a lot depending on the oil's source and whether it was vacuum distilled, until they meet the specifications. Number 6 can just be given a lower value, as who knows how long the carbon chains could get. -- Kjkolb 02:24, 13 December 2005 (UTC)

Perhaps you could fill in the lengths for the first to rows and put "various" or some such for the other types Cafe Nervosa | talk 02:48, 13 December 2005 (UTC)
I took my best guesses from the information I have. I don't have much information for number 3. I don't even know if it's pure distillate or if it's mixed with a little number 6. -- Kjkolb 01:08, 14 December 2005 (UTC)

I notice the article for #2 heating oil states chain length from 14 to 20, whereas the article for diesel states chain length from 10 to 15, so perhaps "diesel" and "heating oil" are not exactly the same? N3362 03:44, 16 July 2006 (UTC)

I would advocate adding boiling point ranges to the table and removing carbon number. I'll double check the standard and edit accordingly. --EnergyMan 14:19, 22 August 2006 (UTC)

Boiling points[edit]

Petrocard shows the boiling point of No.2 Diesel to be between 320°F to 700°F (160° C to 371° C) I'm curious if the boiling points mentioned in the article should not be degrees F rather than degrees C. It's difficult to believe the article's quoted temperatures of 370 to 600 °C (698° F - 1112° F) as boiling points. -- (slightly modified by Kjkolb)

I lowered the boiling point range to 175 C, since that's what How Stuff Works has for kerosene, which is fuel oil #1. As for the higher number, it should be remembered that that is the upper boiling point for fuel oil #6, which is very heavy and viscous. -- Kjkolb 19:56, 7 February 2006 (UTC)

I will work on b.p. ranges this week. --EnergyMan 14:19, 22 August 2006 (UTC)

Boiling points for fuel aren't necessarily as important for the folks that use the fuel as flash point. Working on board ships as a marine engineer, I've dealt with MGO and MDO. My understanding of the Coast Guard regulations concerning fuels is the flash point of fuels used cannot be less than 140 degrees fahrenheit. On just about all commercial ships (container ships, tankers, Ro/Ro's, etc...) you'll most often see #6 Diesel used. In dealing with #6, it is often kept in the storage tanks at atmospheric temperature (where it often has the consistency of tar, maybe a little less viscous) then when it comes to pumping it, steam coils in the tanks often heat the fuel to just below the flash point to pump it to the daily storage/settler tanks, then from there it is heated again before being delivered to the Main Engine/Boiler(s). Hengineer 10:33, 29 August 2006 (UTC)

Change "No" to "#"[edit]

Does anyone think this article should be changed from "No" to # for all the fuels, its so hard to read because i constantly keep thinking no.Patcat88 21:38, 18 October 2006 (UTC)

In my research, I mostly saw "No." used. The cases where "#" was used were mostly when there was not much room, such as in charts. I prefer to keep it, but if it is a significant problem for many people, then I suppose it could be changed. The usage should be noted in that case. It might be preferable to use "number" instead of #. I'd have to see how it looks to decide. -- Kjkolb 09:28, 9 November 2006 (UTC)


No. 6 oil must, in fact, be stored at around 100°F (37.8°C) heated to 150°F (65.6°C)–250°F (121.1°C) before it can be easily pumped, and in cooler temperatures it can congeal into a tarry semisolid. The flash point of most blends of No. 6 oil is, incidentally, about 150°F (65.6°C).

So #6 must be heated to 150 degrees before it is pumped, but at 150 degrees it also catches fire. Is it always pressurized or something, or is the article being self-conflicting?

note: you are mixing "flash point" with "fire point" or "kindling point" three different temperature points.

Addition: Flash points of these bunker fuels are always more than 60°C for safety reasons since it is also stored at that temperature. However, even if its flash point is close to its storage temperature, it simply means it might flash. The fire point of these fuels can be as much as 30°C above its flash point. The fire point is the temperature where a 'flash' can continuously sustain a fire, whereas flash point just means a 'flash' that happens and disappears almost instantly. Therefore, a fire is not a flash, but a flash can create a fire or flash fire. Hope this clears some doubts Venny85 (talk)

Is "expert attention needed" tag still valid?[edit]

The section on bunker oil has a tag of 'expert attention needed' just before the table. I'm not an expert, but the section looks pretty clear to me, and there seem to be a bunch of pretty good experts here working on the article.

Would it be reasonable to remove that tag? Loren.wilton (talk) 13:15, 13 December 2008 (UTC)

Done. Thewellman (talk) 21:07, 11 December 2013 (UTC)

Is viscosity of fuels affects the performance of Engines[edit]

Can somebody make a comment on this, is viscosity of fuel affects the performance of an engine, what is the difference between using light and heavy oil, does it affect the performance of engine —Preceding unsigned comment added by (talk) 09:14, 19 February 2009 (UTC)

Marine Fuels and fuel viscosity[edit]

Marine Fuels and fuel viscosity: Heavy fuel oil requires heating both to make it pumpable and for combustion. It may be used for engines or burners and the degree of fuel processing varies accordingly. However, in both cases the viscosity is important. The fuel is atomised as it passes through the injectors of an engine or the nozzles of a burner. The optimum combustion efficiency and least pollution occurs with a particular size of fuel droplet. Droplet size affects the behaviour of the droplet, how it disperses in the combustion region, how quickly and completely it burns and thus the amount of pollution released. The droplet size is affected by the viscosity. If the viscosity is too low then a fine mist is formed which does not disperse very easily, and does not project well from the nozzle or injector and hence, becuase the distribution is poor, it does not mix so well with the air. This means it takes longer to burn, burns incompletely and burns in the region of the injector or nozzle. Incomplete combustion results in excess pollution. If the viscosity is too high the droplets are larger, but instead of collecting around the nozzle or injector, they tend to be propelled across the combustion space. The result is a again a less well dispersed volume of fuel droplets which again do not mix well with the air. They take longer to burn and burn less completely. The combustion this time takes place on the surfaces of the combustion chamber or on the boiler tubes, if a burner. However, if the viscosity is optimised then the droplets are well distributed throughout the combustion area (or burning zone in a burner) and they then mix well with the air and thus burn more efficiently, burn more completely and burn where it delivers the its energy in the most efficient manner.

For engines the optimum viscosity is typically in the region of 10-15cst but it can be higher for burners. The difference between engines and burners becomes apparent when it is considered how the fuel viscosity is optimised. There are two ways the fuel viscosity is optimised; primarily by blending the high viscosity residual fuel with low value low viscosity cutter stocks to produce fuels which have a nominal viscosity at the reference temperature. Secondly by heating the selected fuel to reduce its viscosity. Thus some engines or burners will use a low viscosity fuel and others are able to manage a much higher viscosity fuel. Fuel fuel oil viscosity, for large diesel engines, is regulated by means of a viscometer in the high pressure circuit which regulates the viscosity to the optimum value by controlling the heating of the fuel. The original viscometer used was the Halikainen inline capillary viscometer ( In the capillary viscometer, a small portion of the flowing oil is pumped through a capillary at a precisely controlled flowrate. The pressure drop across the capillary is then a function only of the viscosity. The Halikainen was around 1% accurate but it was superseded by the twin capillary viscometer manufactured by VAF. Twin capillaries reduce measurement problems e.g. due to pressure drops across the tube due to the flowing fuel, and by adopting a larger diameter capillary machined from Teflon or PTFE, the resultant viscometer, even though less accurate than the Halikainen, is more practicable and this technology dominated the marine market for over 40 years.

However, fuel to engines is centrifuged and filtered because engines tend not to respond well to the particulates and other contaminants, but burners are far less troubled by fuel quality and the fuel is less thoroughly processed. This is an important difference because the capillary viscometer is sensitive to particulates and thus has not been successful in burner applications.

For burners, the approach to controlling fuel viscosity is more complex. It usually depends on samples of the fuel being taken at regular intervals to determine the injection temperature (the temperature at which the viscosity of the fuel will be the optimum for combustion; otherwise also known as the EVT value or Equi-Viscous Temperature). The fuel temperature of the fuel is measured online and used to control the fuel heaters such that the EVT value is maintained. The problem with this is that fuel quality can be variable and viscosity is very sensitive to even small changes in quality. The laboratory analysis must be repeated regularly and further measures are often necessary to compensate for quality changes. This includes increasing the excess oxygen flow and visual flame inspection. Even so the result s that soot blowing and tube burn outs can be more prevalent than if the viscosity could be measured.

Changes in the marine industry toward unmanned machinery space and de-manning and de-skilling have meant that the capillary viscometers have now largely been superseded by vibrating element viscometers which are virtually maintenance and calibration free, and some of these viscometers are also suitable for burner fuels as well as engine fuels since they are far less sensitive to dirt or particulates. Digital viscometers can be more accurate and much faster responding which means a more stable control of the fuel oil heaters and thus some further improvements in efficiency.

Marine Fuel Oil Grades

In the marine industry today one of the more common standards is ISO 8217 2005E which now lists fewer fuel grades than the preceding standard or the CIMAC standard (derived from the earlier British standard BS MA 100) and includes limits on marker elements to restrict the use of heavy fuel oils as dumping grounds for waste chemicals and used lubricants. It is increasingly aligned with MARPOL Annex VI (the marine atmospheric pollution legislation) to reflect the sulphur content limits. However, the standard often set maximum value limits for the various properties and thus the actual properties of a fuel may vary significantly from one batch of fuel to another. Many marine fuels are not covered by the standard but are subject to conditions in the bunker supply contracts which reflect the engine manufacturer's guidelines. There range of fuels actually supplied exceeds those listed in the dstandards and this means that 500cst fuels and 750cst fuels or higher do not appear in the ISO 8217 standard. e.g. intermediate fuels such as IF 30, heavy fuels such as 180cst and 380cst and, more recently, 500cst. Incidentally, the fuel standards usually referred to fuels by their viscosity at 100degC which is the usual reference temperature in the refineries. Hence G35, H35 and K35 are all fuels with a viscosity of 35cst at 100degC. In the marine industry these fuels are usually simply referred to by their viscosity at 50degC, a more convenient temperature for reference when analysing off line e.g. on board vessels or on fuel barges. Hence the above fuels (according to CIMAC) are all 390cst at 50degC.

ISO 8217 2005E now uses 50degC as the reference temperature.

The problem for the industry is the cost of fuels. Heavy fuel oil is less expensive than MGO or MDO typically close to half the price. The heavy grades of fuel are cheaper the higher the viscosity. This is because most fuel oils are a blend of residual oil and low value low viscosity cutter stock but the cutter stock is the more expensive component. Hence, the less cutter stock, the higher the viscosity and the less the cost. The main advantage of 500cst fuel over 380cst fuel is the lower cost of this fuel.

Despite the low cost of heavy fuel oils and the small differences in price resulting from the amount of cutter stock used, because ships burn so much fuel (it can be as much as 70-80% of the operating costs) these small differences are important. SO much so that the ideal is to blend fuels specifically for the engine and increasingly engine manufacturers and vessel operators are interested in blending fuels at the engine. The optimum fuel blend is one that has the highest EVT or injection temperature consistent with the ability of the fuel treatment system and the engine to handle it. The energy to heat the fuel is derived from the exhaust gases (essentially a waste product of combustion on a vessel where there is surplus heat) so the limit to heating is in the capacity of the heat exchangers. The temperature limit is determined by the engine components e.g. the injections and fuel pumps.

For a typical engine the optimum injection viscosity may be 11cst and the maximum permissible temperature 150degC. If the engine usually burns a 380cst fuel the injection temperature is around 140degc. hence the fuel is not optimal. By increasing the fuel viscosity to 610cst,the injection temperature increases to 150deg. However, at one time there were no suitable fuels between 380cst and 750cst and hence many older vessels have heaters that cannot raises the temperature as high as necessary but those that can are able to use the 500cst fuels available. The injection temperature for a 500cst fuel is typically around 146degC which is still short of the desired optimum hence if vessels bunkered 750cst fuel and blended it at the engine to 610cst or marginally less then the fuel costs can be further reduced.

For temperature viscosity calculations visit and download "RMI ASTM D341 Rev01.xls". —Preceding unsigned comment added by (talk) 20:09, 22 March 2009 (UTC)

Fuel Oil Management System (FOMS)[edit]

Recently the students of Air University Pakistan are taking Fuel Oil Management System as their final year project. In this project, they shall monitor as well as control fuel oil (also known as furnace oil) from any remote location using Programmable Logic Controller (PLC) and Supervisiory Control and Data Acqusition(SCADA) system. Technical help is being provided by Nation Transmission and Despatch Company (NTDC). In future NTDC is planning to take over all power plants of Pakistan and this project will be of great help to the. —Preceding unsigned comment added by (talk) 04:21, 13 May 2009 (UTC)

Recent developments[edit]

As merchant navy chief engineer I use bunker fuels for the main engine and auxiliary engines on board. (around 30,000 kW and 4 x 2000 kW). Since end of 2008 also grade RMK 850 is available. Apart from the viscosity it has similar caracteristics as RMK 700. The higher viscosity means 3 ºC more heating compared to RMK 700 to get the desired viscosity of 11-13 cSt at injection. For RMK 700 this means heating to150 ºC. As engines are designed to a max. fuel temperature of 150 ºC, most enginebuilders have made this the limit and as a result accepted that RMK 850 can be injected at 150 ºC with a viscosity of 15 cSt.

A drawback is that the heavier the fuel, the lower the Low Caloric Value. As bunker fuels are bought by the ton, it means less energy per kilogram and this has an negative impact on the efficiency of the engine. To compare: RMK 700 can have a density of 1007 kg/m3 and a LCV of 39,560 kJ/kg. Standard calculations are based on a LCV of 40,700 kJ/kg.

For ignition qualities the unit CCAI = Calculated Carbon Aromatic Index is used, rather than the Cetane Index. Typical values are around 865. Pourpoint is unpractical, on ships a transfer temperature is needed to prevent damaging the fuel transferpumps. A fuel with a pourpoint of 20 ºC still needs a transfertemperature of 50 ºC. Vanadium is important as with high exhaust gas temperatures it can form ash deposits on the turbo chargers. Limit is 600 mg/kg. Aluminium and Silicon are remains of the katalytic process to break bitumen molecules into smaller fractions. They take no part in the combustion process in the engine but give extra wear to the fuel pumps and atomizers.

Sulfur content is getting more and more attention from coastal states. In Europe complete seas (“SECA”, Sulphur Emission Control Areas) are limited to fuel consumption with fuel of max 1.0 % and alongside in ports 0.1 % of Sulphur by mass, getting more stringent in 2015. New Zealand and Hong Kong allow fuel with max Sulphur content of 0.5 % when alongside. The state of California also has some rules. Zwart Chief Engineer Maersk Line — Preceding unsigned comment added by (talk) 16:19, 11 July 2011 (UTC)

How to parse this sentence?[edit]

Broadly speaking, fuel oil is any liquid petroleum product that is burned in a furnace or boiler for the generation of heat or used in an engine for the generation of power, except oils having a flash point of approximately 40 °C (104 °F) and oils burned in cotton or wool-wick burners. I'm not sure what that's trying to say. Are "oils burned in cotton or wool-wick burners" considered fuel oil, or not? -- RoySmith (talk) 10:38, 10 July 2012 (UTC)

As I read it, they are not. I can't see the fuel oils talked about here being suitable for wick burning (too dense to wick up), and the lack of a comma after (104 °F) indicates that the next clause is in the 'except' group, not in the 'fuel oil is any liquid petroleum product that' group. Peridon (talk) 15:06, 15 August 2014 (UTC)


In the Maritime section, it says: "MFO (Marine fuel oil) - same as HDO (just another "naming")". OK. But what is HDO? It's not mentioned anywhere in the article. Peridon (talk) 15:02, 15 August 2014 (UTC)

Is it safe to assume HDO is a typo for MDO?Robocon1 (talk) 11:44, 8 January 2017 (UTC)

Mitsubishi Heavy Industries manufactures generator for power plant, one type says MFO engine aside from natural gas type and diesel engine type. In 2015 there's a shift of using MFO engines in Indonesia. I hope to find out more before updating here.YogiHalim (talk) 08:04, 26 May 2017 (UTC)

Request for global quantities used information[edit]

It would be useful if there was a section on the amount of fuel oil used globally, and by sector (Marine, ...). Briancady413 (talk) 17:22, 19 September 2016 (UTC)


The classes detailed in this section of the article are essentially the American ones. It would be useful if the viscosities for these could be added to enable comparison with classifications in other countries.

The UK, for example, has the standard BS2869 which defines Class C2 (kerosene, max 2 mm²/s @ 40°C) and Class D (gas oil, max 5.5 mm²/s @ 40°C) distillate oils, and Class E (light fuel oil, max 8 mm²/s @ 100°C), Class F (medium fuel oil, max 20 mm²/s @ 100°C), and Class G (heavy fuel oil, max 40 mm²/s @ 100°C) residual oils.

German standard DIN 51603 has, among others, heating oil EL ("extra-light", max 6 mm²/s @ 20°C) and heating oil S ("heavy", max 50 mm²/s @ 100°C).

The American classes are interesting and important to the article, but without a point of reference they are meaningless to the non-American reader. I would gripe at the predominant use of °F (USA) rather than °C (every country except the USA) at this point too, but I don't want to start off any flaming. Especially not with all that oil around...

P M C 16:44, 18 February 2017 (UTC)

Looks like you've written most of the section already. Write it up! Add it in! And if we didn't have an article with units in degrees F, we'd still be waiting for an article written with units in C. --Wtshymanski (talk) 01:14, 21 February 2017 (UTC)
I'd be happy to, but without the viscosities for the US grades I can't make a comparison. I could hazard a guess, but I don't think thats a good idea! If nothing else, it would be OR...

P M C 15:51, 27 February 2017 (UTC)