# Diesel rated by Cetane not Octane- but what do our deisels require?



## Kanuck (Feb 18, 2003)

d geek said:


> One fuel that Canada has (but isn't available in US) is Shell V-Power, which has 50 cetane IIRC.


I believe I get better mileage when I use Shell V-Power diesel but it is difficult to do a true "apples to apples" comparison. It normally costs about 3¢/litre (11¢/gallon) more, so probably worth it.


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## Max Schnell (Jun 22, 2011)

Just FYI

There are basically 2 grades of on-road diesel...historically #1 and #2. #2 is the the most common variety ...is considered "regular" and generally has a cetane rating (number) of 40 to 43. They do not publish this number at most stations. The highest the cetane number the more desirable the fuel because it has better combustion qualities.

#1 or premium diesel has a cetane rating of 44 to 45. It is lighter and burn more completely than #2 and as such will generally yield better fuel consumption. However it is more expensive. I have personally experienced a 25% increase in fuel mileage using #1 vs #2. So anytime I have the chance to use premium I will as the cost of premium diesel is NOT 25% more than regular.

Kerosene (jet fuel) is for al practical purposes #1 diesel. You can burn it in any variable speed diesel engine with no damage. However it doesn't have quite the lubricity of pump diesel and as such may ( I re-iterate MAY) increase wear on the fuel injectors of any diesel over time. However burning kerosene will not hurt your engine occasionally and you will likely see an increase in fuel mileage like that of #1 pump diesel. The reason I mention this is if in a pinch you need fuel and kerosene is readily available do not hesitate to use it.


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## Penguin (Aug 31, 2003)

Max Schnell said:


> Just FYI
> 
> There are basically 2 grades of on-road diesel...historically #1 and #2. #2 is the the most common variety ...is considered "regular" and generally has a cetane rating (number) of 40 to 43. They do not publish this number at most stations. The highest the cetane number the more desirable the fuel because it has better combustion qualities.
> 
> ...


I do not believe all Kerosene is ULSD fuel and, if not, will damage the emissions system. If you do try kerosene, make sure it is Ultra-Low Sulfur.

This is the first time I have ever heard anyone claim #1 diesel provides better MPG than #2... everywhere else the claim is that #2 has higher BTU content and provides better MPG than #1. The information I have seen attributes part of the MPG reduction people in colder climates see with their diesels to the addition/blending of #1 diesel into the #2 diesel to make a "winter diesel" which will not gel or form paraffin crystals/particles and clog the fuel filter.

Do you have any reference or source which supports #1 diesel providing better MPG than #2 diesel? You may very well be correct; however, this is the first time I have seen such a claim for #1 diesel and I'd be interested in learning more and the reason why.


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## 62Lincoln (Sep 26, 2004)

Penguin said:


> I do not believe all Kerosene is ULSD fuel and, if not, will damage the emissions system. If you do try kerosene, make sure it is Ultra-Low Sulfur.


This is critical with our engine's DPF system.


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## d geek (Nov 26, 2008)

Max Schnell said:


> ...#1 or premium diesel has a cetane rating of 44 to 45. It is lighter and burn more completely than #2 and as such will generally yield better fuel consumption. However it is more expensive. I have personally experienced a 25% increase in fuel mileage using #1 vs #2. So anytime I have the chance to use premium I will as the cost of premium diesel is NOT 25% more than regular.
> 
> Kerosene (jet fuel) is for al practical purposes #1 diesel. You can burn it in any variable speed diesel engine with no damage. However it doesn't have quite the lubricity of pump diesel and as such may ( I re-iterate MAY) increase wear on the fuel injectors of any diesel over time. However burning kerosene will not hurt your engine occasionally and you will likely see an increase in fuel mileage like that of #1 pump diesel. The reason I mention this is if in a pinch you need fuel and kerosene is readily available do not hesitate to use it.


This is incorrect info that could get someone in trouble. #1 Diesel is for all practical purposes kerosene (NOT premium diesel) and should *never *be put into a modern diesel engine in a pure form. :yikes: It is used to winterize diesel to prevent gelling in colder climes.

Premium diesel (if you can anctually find it) is a #2 diesel fuel with a few improved attributes (higher cetane being one of them). As far as I know the National Council of Weights and Measures definition of premium diesel was never formally adopted. I know in this state that retailers are allowed to put a "premium" label on any pump they please- with no additional criteria being met!


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## floydarogers (Oct 11, 2010)

Interestingly, the PDF posted in the "Everything you wanted to know ..." thread says that Cetane 51 is the fuel spec. I wonder if that's a European rating...

I've been wondering a lot lately on the varying MPG's posted in several threads. I changed stations recently when one brand became cheaper, and it seems I'm getting better mileage.


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## Max Schnell (Jun 22, 2011)

Jet fuel is chemically similar to diesel fuel, and most diesel engines are capable of burning any type of jet fuel. In fact, many major airports around the world make a point to employ ground vehicles that have diesel engines, so that they have the option of running on jet fuel. This helps to reduce the number of different fuels that must be stored at the airport. Jet fuels are more expensive than regular diesel as they are produced to tighter standards and also usually have more additives.

These may be of interest:

http://www.tdiclub.com/articles/Diesel_Fuel_Guidlines/

http://dodgeram.org/tech/dsl/FAQ/diesel_fuel.htm

http://www.astm.org/Standards/D613.htm

Here's a sales pitch from Universal that claims Premium Diesel will result in better fuel economy. Buy then consider the source.

http://www.universaloil.com/premium_diesel_fuels.php

Additonally Octane and cetane are both measurements of ignition performance, but they represent completely opposite performance characteristics.

To put it another way, octane represents the fuel's ability to resist pre-ignition. In diesels, just the opposite is desired because compression IS the ignition source not a spark. So faster ignition is desirable in diesel engines. It results in more complete combustion. The fuel should readily ignite, and cetane is a measurment of that characteristic. Generally, diesel cetane falls around low to mid 40s. Premium diesel is 50+ cetane.

Here's a quote from a petroleum engineer friend of mine that works at a refinery in Houston:

*The Cetane Number you see on the diesel pump at the service station, is an indication of the ignition quality of the diesel fuel. Ignition quality is the ability of the fuel to ignite and burn. The higher the Cetane Number, the faster the fuel burns, or the shorter the time between the entry of the fuel into the cylinder until it ignites.

Cetane itself is actually a clear liquid hydrocarbon which ignites very very easily. Using the Cetane as a test fuel it is compared with diesel fuel to determine the ignition quality of the diesel fuel. The Cetane rating scale ranges from 1 to 100, with Cetane itself at the top of the scale at 100.

As I mentioned in my earlier , Number 1 Diesel Fuel has a Cetane Number of 44 or 45 and Number 2 Diesel Fuel has a Cetane Number of 40. Whenever you see a pump labeled "Premium Diesel," they're usually talking about Number 1 Diesel Fuel. Since Number 1 Diesel Fuel has a higher Cetane Number, it will ignite easier and is good for use in cold weather.*

While it is true that #2 diesel has very slightly more energy per unit volume it is also true that #1 burns much more readily. In other words...in a diesel engine... it doesn't matter if the fuel has a higher energy content if the engine does burn the fuel COMPLETELY. #1 diesel has a higher cetane rating....and thus has better ignition qualities (burns more readily or efficiently) and should result in better fuel economy and performance.

But it is very hard to find and is generally used only in the winter because of it's quality to combust even in cold temps.

Hope that helps. Odds are it just "muddied" the proverbial waters. :dunno:


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## Max Schnell (Jun 22, 2011)

One more thing:

If you are an old diesel guy like me you know from experience the addition of certain fuel additives can increase your fuel efficiency. These additives simply make the diesel more readily combustable. 

However I read where BMW does not recommend using ANY FUEL ADDITIVES in the 335d. Is that true?


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## Snipe656 (Oct 22, 2009)

Max Schnell said:


> As I mentioned in my earlier , Number 1 Diesel Fuel has a Cetane Number of 44 or 45 and Number 2 Diesel Fuel has a Cetane Number of 40. Whenever you see a pump labeled "Premium Diesel," they're usually talking about Number 1 Diesel Fuel. Since Number 1 Diesel Fuel has a higher Cetane Number, it will ignite easier and is good for use in cold weather.[/B]:


I think that statement about if it says Premium Diesel then it probably is number one is false or at least down here. Up until this past year almost all Shell stations had signs that said "Premium Diesel". They however were not selling number one at all.

I honestly don't recall ever seeing number one at a pump. I probably have and just don't remember it.

Sent from my iPad Nano


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## floydarogers (Oct 11, 2010)

Max Schnell said:


> Jet fuel is chemically similar to diesel fuel, and most diesel engines are capable of burning any type of jet fuel. In fact, many major airports around the world make a point to employ ground vehicles that have diesel engines, so that they have the option of running on jet fuel. This helps to reduce the number of different fuels that must be stored at the airport.
> 
> Hope that helps. Odds are it just "muddied" the proverbial waters. :dunno:


1) Jet fuel is allowed to contain far more sulfur than our ultra-low-sulfer diesel. I doubt that airport operators are allowed to use it any more (or only in older vehicles.) Too much soot.

2) One should note that there is a definite difference between FUEL-OIL #1 (kerosene), FUEL-OIL #2 (diesels), FUEL-OIL #3 etc. and the #1 & #2 attached as you have to DIESEL. They are used in similar methods (delineating different fractions).


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