#2, #1, Jet A... and lubricity.

I just had a conversation with someone who doesn't think kerosene or jet fuel is an any more dry than #2, and doesn't think it poses a threat to injector/pump systems.

I've heard (and read and searched) a million times that you need to add ashless 2cycle oil for lubricity if you run jet fuel. But I've never seen anything proving it. Saying "everyone uses 2-cycle oil" doesn't hold up well in an arguemnet with someone who supposedly worked in a Mobil lab.

Do any of you know where I could look to find information on this? Maybe comparing lubricity or wear, or some horror stories from people who didn't add something for lubricity.

Any links or even just some hints for a good Google would be appreicated.

Thanks,
Nick

Well, if the diesel engine has a fuel pump that uses engine oil for lubrication, then fuel lubricity is not critical. But for rotory fuel pumps that use fuel for all lubrication as TDIs use, fuel lubricity is a big deal.

I suggest you stop by your local diesel injection repair shop and talk to the technicians. They will have pictures and probably actual pump parts laying around showing the results of poor fuel lubricity. Then you decide if kerosine, #1 fuel oil, or jet fuel is OK to use.

Brian, 97 Passat TDI

Jet Fuel has the lubricity nearly as bad as gasoline. Jet engines can run gasoline (depending on manufacturer) for a given period of time between overhauls...limitation being lead build up on the turbine wheels!

The VE pumps in our cars do not have bearings but instead use the film of diesel fuel as the only lubricatn to prevent the four rollers from scuffing and wearing into their support pins. The plunger also relies on the lubricity of #2 to prevent scuffing of the plunger bore.

Older diesel used to run fine on Jet-A and the other fractions of kerosene BUT they also only ran at 1700 psi verses the nearly 20,000 of a TDI.

If you want to experiment with free sump fuels do so at your own risk but if you do adding anything to increase lubricity is just about mandatory.

DB

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Jet engines can run gasoline (depending on manufacturer) for a given period of time between overhauls...limitation being lead build up on the turbine wheels!


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Does this mean that the restriction on gasoline is for avgas only, and that they can be run on mogas indefinitely (subject to TBO)? After all, automotive gasoline is unleaded, so it won't build up lead on the turbine wheels.

Military jet fuels (JP-4 etc) are up to 75% gasoline, although they are now changing to commercial spec JET-A1, which is pure kerosene and safer to handle. The reasons for JP fuels were partly to do with the freezing point of fuel (for Jet A1 I think is around -40 C, although feel free to correct this). JP fuels have a lower FP. This is obviously an important factor for aircraft flying at high altitude. 100% gasoline does not work too well as it's Cetane level is too low (if its high octane avgas - cetane is the inverse of octane). Remember that a gas turbine is a compression ignition engine, like a diesel, although continuous, with lighter plugs to get the thing started or relight.

On my engines now I am limited to 150 gallons of Avgas between overhauls, can I run more than that? Well there is no reason too since Jet-A is so much cheaper than 100LL. I am required per the manufacturer (Pilatus) to use "Prist" or MIL equivalent when ambient flight conditions will drop below 0C...Since I am always in the mid to upper Flight Levels for cruise I don't think there is ever a time when I do not need to use an anti-icing additive.

Getting back to JP-4, the fact it has 100LL mixed in does concern me in terms of buildup on the turbo. I have found residues in the past on gasoline turbos. Since a TDI does not operate anywhere near the temps of a gasser turbine fouling is a legitamate concern...HOWEVER JP-4 is very rare in GA (General Aviation). The only time I ever had to worry about it is when flying out of Military bases and again they always had a ready supply of Jet-A with additive pre-mixed.

DB

I have no official data to support my next statement other than personal experience.

When I get #2 diesel on my hands, I wash the oily film off with a good hand cleaner. When I get Jet A on my hands, I flush them with IA, then wash with a quality hand cleaner, then apply hand lotion. If I don't follow this procedure, my hands will get extremely dry very quickly.

This leads me to believe that Jet A is much drier than #2 diesel.

I used to have an 81' Jetta 1.6 that I ran on sump Jet A alot. I would fill the tank and add 1ea 8 oz can of Marvel Mystery Oil per a recommendation from a Dodge Cummins owner that ran his on Jet A. He would only run a 50% mix though.

Neither one of use had any fuel related problems. My Jetta exhaust smoke would drop dramatically . The cold start was also greatly shortened.

I didn't see this topic till I did a search on Jet A, sparked by a recent update I got on diesel aircraft engine receiving FAA Type Certificate. http://www.thielert.com/en/aircraft_industry/tae_125/tae_125.html

This puppy can run on diesel or Jet A in any combination. It's pretty much a VW TDI with common rail direct injection. Maybe lubricity isn't a big issue with Jet A fuel. /images/graemlins/rolleyes.gif

Where do they sell #1? I have always assumed all diesel sold at gas bars was #2 but I have never paid attention to see what # was going in. Should I be watching this?

I run my TDI on Jet A all the time but I mix 4 oz of ashless 2 cycle oil for every 5 gallons or 12 0z per tank full. Straight Jet A will shorten the life of your pump greatly. Rub a few drops between your fingers... it's as dry as gasoline. In Canada we have to watch out for Jet B which smells and feels just like Jet A but it contains 40% napthaline or white gas. It explodes just like gas too whereas Jet A like diesel burns. Helicopeter operators like Jet B because it is soot free compared to Jet A. I guess they like clean tail booms.
When I used to fly behind PT6 gas turbines they would allow a few hours in the TBO cycle on Av Gas but putting gas in your tank was really an emergency measure at best. I only remember adding av gas once when I was stuck up the coast of Hudsons Bay and it made the engine run hot as hell.
The Pw 123 gas turbines I sit behind now will not allow anything but Jet A or B to be used at $2.5 mil per engine I won't argue.
When I was at Oshkosh this year I examined 2 aero diesels both had completely different injection systems from our TDI's
2 cycle oil is cheap insurance really and it's great lubrication for the pump and injectors.
I have 150,000 Km/93,000 miles and i would estimate half the mileage is on sump fuel.

If anyone has more miles on their Type 4 TDI burning Jet A I would like to hear from them.
Cheers

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BlueKnight said: Where do they sell #1? I have always assumed all diesel sold at gas bars was #2 but I have never paid attention to see what # was going in. Should I be watching this?

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__. I've been alarmed at the use of "#1" occasionally in reference to diesel fuel. I'm not a petroleum expert but all my experience seems to indicate that people who are use "#1" to refer to a lighter, less-likely-to-gel, lower-BTU middle petroleum distillate which is either 1) a diesel fuel which is very much like kerosene, or 2) kerosene which is being used as a diesel fuel. But I have noticed a few (generally the rotest of the rot-gut) retailers attempting to get some "branding" cachet by selling their end-of-lot, other-peoples'-reject, low-quality scum as "absolutely, top-quality, #1 diesel fuel". I'm pretty sure that this stuff that's been listed as "#1" is #1 only in their fantasy as to what will help sell the stuff and not #1 in the refinery sense, but being used in this way seems to muddy the water.

__.Of course, the research paper quoted by the link above is likely to use the term more accurately. I'm assuming that in "minus-degree" Alberta (where the people who are pushing their product with this "research" paper are located) a fair amount of #1 diesel is mixed into regular diesel fuel as a winter mix, or even may be used straight as a winter fuel. The latter seems implied by the paper -- or the paper may be using the term "#1" to refer to what might be more properly described as "winter mix of #1 middle petroleum distillate and #2 diesel fuel". It's not made clear in the paper.

#1 diesel has a certain amount of lubricity, not as much as #2. You can run straight #1 in extreme conditions if you have to. It is not wise to do it for extended periods without adding some type of lubrication. #1 is a hotter fuel and can burn injectors, pistons, and turbos. Again this is under extreme conditions, such as running it in hot climates. In a lot of cases jobbers in northern climates will blend #1 and #2 together to prevent gelling, refinerys will already be stepping up blending for fuels shipped to northern climates. Double whammy in some cases, resulting in fuel mileage drops and poor performance.

Jet A, B, JP-4, JP-8, and other aviation grade kerosenes are extremly dry and carry little to no lubricity. They also burn much faster and hotter than #1 at a rate of more than 20'F . I had to run straight JP-4 once in a older Cummins because I ran out of diesel and had a load of JP. It ran extremly hot for the 15 miles I went, pyrometer temps (EGTs) in the 1400', just babying it in.

I would not burn Jet-A or any aviation fuels in a TDI. I have on occasion, put a little 100LL AVgas in my bike, it can be a fun ride. /images/graemlins/smile.gif

Ok, I sent a message to the Centurion Engines, maker of the diesel aircraft engines, which recently got US FAA approval, asking about lubricity and turbine fuel. Following my question and their response.
Question:

A question about the engine and fuel. I read that the engine can run on
any mixture of diesel and Jet A. How is the fuel lubricity affect the
injection pump. Similar auto engines running diesel I have heard may be
harmed by Jet A due to lack of lubricity. (Maybe this was just rumor)
Or is there a specially designed pump? Also is there redundancy for the
injection pump?
Thanks

Response:
As far as lubricity of Jet fuel is concerned you are exactly right. We have
specifically developed the high pressure pump components. This includes
using new materials, revised manufacturing methods, special surface
covering, treatment and testing procedures. This high pressure pump is
redundant in itself as it incorporates three separate pistons. During the
operation the duty cycle value is constantly monitored and recorded in the
data logging system. Defined duty cycle limits are used to monitor the
condition. This ensures that long before you would notice any misbehavior in
engine performance or running characteristics the system sends a signal to
the caution light.

Please visit us regularly on: www.centurion-engines.com
end

Well, this just confirms what everyone was saying, but, that there is a way to make pumps tolerant of low lubricity fuels. FWIW /images/graemlins/wink.gif

All the corporate jet types that I've flown (and the Turbo Commander, if I'm not mistaken) allow some small amount of avgas to be run, like 150 gallons between hot sections. But they only allowed 80/87 octane. No 100LL or 110/130.
Just found this reply from Chevron on another thread about kerosene:
You are quite correct to say K1 kerosene is a different "animal" than Diesel # 2. It is, however, very close to the same fuel as Diesel # 1. I will note some differences later.

The most important thing to remember is that Chevron would never advise anyone to use a product in a piece of equipment if the equipment manufacturer did not also agree that the fuel was correct for use in its equipment.

K1 kerosene is a low-sulfur kerosene that is made for use in space heaters, lamps, etc. - and not for use in vehicles or generators. It is also not taxed so would be illegal to use in "on-road" vehicles.

Some of the differences between the three fuels would be

Viscosity

Four semi-annual surveys for years 1990-1992 showed national averages as such for viscosity (represented in milliPascal-seconds (mPa . s)(=centipoise) cSt)

Diesel # 1 1.33
Kerosene 1.63
Diesel # 2 3.20

Lower lubricity is likely as the viscosity decreases. While this may not cause catastrophic instant damage, it could cause long-term wear of pumps, etc.

Flash Point

Diesel # 1 and Kerosene both have lower flash points than Diesel # 2 and are therefore somewhat more hazardous.

BTU's

Both Kerosene and Diesel # 1 are less dense than Diesel # 2 and will thus have a slight reduction (~3%) in BTU per gallon. This would likely be reflected in lower fuel economy.

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Milehog said:
Well, this just confirms what everyone was saying, but, that there is a way to make pumps tolerant of low lubricity fuels. FWIW /images/graemlins/wink.gif

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Easily done. Just buy a Dodge Ram pickup with a Cummins engine. The fuel pump is lubricated by engine oil. I've put *ANY* crappy fuel in it and the engine will chug right along with no concern.

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Jet Fuel has the lubricity nearly as bad as gasoline. Jet engines can run gasoline (depending on manufacturer) for a given period of time between overhauls...limitation being lead build up on the turbine wheels!

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second that, a jet engine will run on almost anything, 100LL regular gas diesel whatever you can find, but it isnt the best for it and only in emergencies.

i too asked about running JET A but the comments on the lack of lubricity scared me off it.

just take some jet A in one hand and rub it in your fingers and do some diesel the same way!
dont skimp to save a few bucks a fill up only to ruin your $1500 injection pump