Diesel fuel facts

#0, Diesel fuel facts
Posted by NoSlack on Jun-25-02 at 05:01 PM

Here is some info I dug up on cetane rating. You might want to ask what the rating is at your favorite fuel stop to see if your getting a grade of fuel for your money. Cn of 40-46 is OK 46 and up is great.
Mike

In the USA, all diesel fuel must meet the specifications set forth by the American Society for Testing and Materials (ASTM). In Canada it is the Canadian General Standards Board. They have web pages at www.astm.org and www.pwgsc.gc.ca. One can order documents for a fee. Diesel fuels are covered in documents ASTM D-975 and CGSB 3.6-M90 and 3.517-93. Their documents cannot be previewed. The CGSB lists the ASTM as a reference, they are that close. All the specifications for cetane, pour points, viscosity, flash point, BTU content, etc., are in these documents.
The most common question, Cetane? What is cetane? Cetane is to diesel fuel what octane is to gasoline. It is a measure of the fuel's ignition quality and performance. Cetane is actually a hydrocarbon chain, its real name is 1-hexadecane. It is written as C16H34, or a chain of 16 carbon atoms with 34 hydrogen atoms attached. All HC chains are also referred to as paraffins. Cetane is a hydrocarbon molecule that ignites very easily under compression, so it was assigned a rating of 100. All the hydrocarbons in diesel fuel are indexed to cetane as to how well they ignite under compression. There is very little actual cetane in diesel fuel.
Most of the hydrocarbons in diesel fuel have similar ignition characteristics as cetane. Cetane is abbreviated as CN. A very loose way to think about cetane is if the fuel has a CN of 45, then the fuel will ignite 45% as well as 100% cetane. Diesel engines run just fine with a CN between 45 to 50. There is no performance or emission advantage to keep raising the CN past 50. After that point the fuel's performance hits a plateau.
Diesel at the pump can be found in two CN ranges: 40-46 for regular diesel, and 45-50 for premium. The minimum CN at the pump is 'suppose' to be 45. The legal minimum cetane rating for #1 and #2 diesel is 40. Most diesel fuel leaves the refinery with a CN of around 42. The CN rating depends on the crude oil the fuel was refined from. It varies so much from tanker to tanker that a consistent CN rating is almost impossible. Distilling diesel is a crude process compared with making gasoline. Gasoline is more of a manufactured product with tighter standards so the octane rating is very consistent. So the CN rating at the pump can be anywhere from 42-46. That's why there is almost never a sticker on a diesel fuel pump for CN.
Premium diesel has additives to improve CN & lubricity, detergents to clean the fuel injectors and minimize carbon deposits, water dispersant, and other additives depending on geographical and seasonal needs. More biocides added in the south in summer, more anti-jell added in the north in winter. Most retailers who sell premium diesel will have little brochures called POPs (Point of Purchase) at the counter explaining what's in their fuel. Please don't ask the poor clerk behind the counter any technical questions after reading this post, all they know how to do is sell you beer, milk, cigarettes, lottery tickets, and take your money.
Texaco and Amoco are two big names who sell premium diesel in limited markets. Amoco mostly sells its Premier to specialized industrial and agricultural markets. I cannot get either in my area. Most fuel retailers buy additives or buy treated fuel. In the northern plain states, Koch is a well known marketer of premium diesel.
Because there are no legal standards for premium diesel yet, it is very hard to know if you are buying the good stuff. An ASTM task force has drafted standards for premium diesel. When the new specifications are accepted, information will have to be posted on the fuel pump. Retailers will no longer be allowed to label cheap blended diesel as 'premium'. They will have separate pumps with clear labels on both informing the customer what in being sold. The marketing and labeling will the same as with regular and premium gasoline. Retailers selling the real thing use this system now. Enforcement of all fuel standards is done on the state level in the USA.
Diesel fuel is an international commodity for industry with no brand name recognition. Because of this it's made as cheap as possible and is transported through most of North America by pipeline. At the area terminal you will see tankers with every oil company logo ever imagined all filling up with the same fuel. So don't get too picky about where you fill up. Shop for price from a large volume retailer so you have the freshest fuel.
The reformulation of diesel fuel in North America is due an international effort for lower emissions. Cleaner diesel emission laws are on the way. Diesel fuel is going to be reformulated into a cleaner fuel in general. Without getting too technical (this is very simplified and over generalized), diesel fuel for the most part is made up of two different hydrocarbon families: paraffin's and aromatics. The paraffin's have a naturally high cetane index, burn clean, but cause that annoying jell problem in winter. The aromatics have a naturally high lubricity, low cetane index, and cause a lot of diesel emissions and soot. Reformulated diesel will have a higher paraffin content, higher cetane number, and a much lower aromatic and sulfur content. It will also be more prone to jelling and have a lower lubricity. Big oil is working on improved additives.
The reason nothing has happened yet is because of infighting in the EPA on its new Tier II Emissions standards for gasoline and diesel. Ultra-clean technology for gasoline and diesel engines is almost ready to go but the refiners have to lower the sulfur level drastically in both fuels. Something should be formally set by the EPA by year 2000, with oil and auto industries whining and slowly complying shortly after.


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#1, RE: Diesel fuel facts
Posted by InlawOutlaws on Jun-26-02 at 02:28 PM
In response to message #0

Great info, but what do you run in your boat, and what additives do you use? I use biobor for the water but nothing else. The habor BOYS are getting after me for the black oily mess left when you run the boat on the trailer, I'll float from now on. Its the nature of the beast, or is there anything I can do to limit the soot? I enjoy your post, especial about the 23 blackmans. I doing the lower end outdrive seal on my now. We fish the 390 sat and the boat ran great 16/17 knots home. Got it on the trailer and my buddy asked about the gear oil coming out of the prop. The joys. Well enough, if you have any suggestions drop a line.
CHUM

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#2, RE: Diesel fuel facts
Posted by NoSlack on Jun-26-02 at 04:51 PM
In response to message #1

The key for me on the fuel was to find a place that moves a lot of fuel and keeps up on their filter changes. I do use a fuel stabilizer if it looks like I'm not going to be using the boat for a few months. (like that's going to happen)
If I'm on the road I use So Cal Truck Stop in National City. It is very clean, lots of room and all 4 pump islands have Red Dye on tap. I stopped by today to check the price($1.16 sales tax included)and cetane rating. I couldn't get any info on the cetane rating out of the lady at the counter so I might have to call the main office for that info.

If I'm on the water, I like Harbor Island Texaco. The service and fuel quality have always been great. The "Blackman price" plus sales tax is generally very close to or a few cents under the truck stop price.

I read up on replacing the seal. If the lower end hasn't been apart in a while, pulling the bearing housing will be the hardest part. If you don't own a Volvo Stern Drive Shop Manual by Clymer, I would strongly suggest picking one up.

When you pull your prop make sure the stainless fish line cutter is behind it.

Mike



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#3, RE: Diesel fuel facts
Posted by Nomad on Jun-26-02 at 07:00 PM
In response to message #1

What the heck is Biobar? I have a lot to learn about diesels I guess!

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#4, RE: Diesel fuel facts
Posted by NoSlack on Jun-26-02 at 07:48 PM
In response to message #3

There are all kinds of after market additives you can buy. The most important thing is a fuel filter/water separator with a clear bowl you can look through. If my fuel looks clear I don't worry about additives. I have a Racor 500 as the first line of defense on my rig. You can chose from 3 different micron elements to run in this filter housing, 2, 10 or 30 micron. The filter mounted on the engine is a 2 so I run a 10 in the Racor.
Additives, where should we start?

Lubricators to cut down on injector pump wear.

Bio guards to kill the bugs. Yes there is a microscopic bug that can bloom in you tank and clog the filters.

Cetain boosters for a better burn.

Stabilizers to keep the fuel from gelling in cold weather.

Stuff to get the water out.

This list goes on and on. If someone thought they had a problem, someone came up with an additives to fix the problem.

I own 3 diesel engines:

Volvo AQAD40A 22 years old, no engine or fuel system failures.

Mercedes 300D 17 years old, 285K mile, no engine or fuel system failures.

Ford F250 16 years old, 100K miles, no engine or fuel system failures.

I'm not a fan of additives. If my fuel looks cloudy I will add something then try to run the tank down as far as possible before refueling.

I believe the fuel manufactures are working very hard to address the cetane and lubrication issues with the newer low emission fuels coming out.

That's my 4 cents worth, for what it's worth.

Mike


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#9, RE: Diesel fuel facts
Posted by Yellowfin1 on Jun-29-02 at 10:01 PM
In response to message #4

Mike,
Thanks for the interesting and informative article on diesel fuel. Your making me wish that I paid more attention in chemistry class.


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#5, RE: Diesel fuel facts
Posted by NoSlack on Jun-26-02 at 10:18 PM
In response to message #3

I forgot to mention the worst thing that can get in your fuel and make you lose power or shut you right down. AIR!!! Yes air is a diesels worst nightmare. Your fuel system must be air tight. Get a little air in the system between starts and she will cough and sputter while filling the whole marina with a light blue smoke. If you suck enough air while running she will shut down just like someone hit the kill switch.
If you get to a point were your engine is harder to start after a few weeks of down time, start looking for an air leak.

The good news is the Volvo 41 should last 15-20 years so you have lots of time to figure this stuff out.

Don't forget we are all just a phone call away if you ever get into trouble.

Mike


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#6, RE: Diesel fuel facts
Posted by InlawOutlaws on Jun-27-02 at 12:36 PM
In response to message #5

Mike, Thanks for the info, I've soaking the lower end for 2 days now and hava a blister from the slide hammer but no movement. I tried a little heat but not sure as to how much. Built a dam around on the seam to hold liquid wrench and to heil marries. I off the see my local mechanic for moral support. In my 75 mercedes diesel I use Red Line additive it seem to quite the valves and less smoke, an old mechanic told me about the stuff. Off the to harbor for help on that lower end.
CHUM

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#7, RE: Diesel fuel facts
Posted by NoSlack on Jun-27-02 at 12:57 PM
In response to message #6

The lower end bearing support can be a tough one to get out. I have a buddy that broke a gear a few years ago and the mechanic burnt all the paint off before it let go.
I pull my outdrive apart every few years just to take a look at the gears and bearing. Pulling it apart regular and lubing the o-rings helps keep things from freezing up.

Mike


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#8, RE: Diesel fuel facts
Posted by InlawOutlaws on Jun-28-02 at 12:01 PM
In response to message #7

mike, I wish you told me that 10 years ago. day 3 so, or 3weeks at the shop. scrapped off paint and 1 can propane no movement
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