Prest

[wrenches and radios]

Can anyone tell me what this stuff does. Can you tell if it's in your fuel? What does it do to a hydro test kit?

[iflyforpie]

Is Prest like Prist?

AFAIK it is an anti-icing additive.

[mag check]

Prist, is also known as FSII, and is in jet fuel when it is shipped to the depot.
Whoever you buy your fuel from tests the fuel in the ground regularly(part of the daily/weekly inspection), to ensure that the proper amount is there.

If memory serves, I think you test it with a refractometer.

[fortis risk]

Some FBO's use an injection system on their trucks making it optional. Some, like PLH integrate FSII it into the system. Still others will hand spray Prist while overwinging an aircraft.

[mag check]

Some FBO's use an injection system on their trucks making it optional. Some, like PLH integrate FSII it into the system. Still others will hand spray Prist while overwinging an aircraft.

Perhaps that is at Shell FBO's?

Esso/Exxon puts it in at the depot, so if you are paying for Prist as well, then I would say you are paying too much/putting too much in your tanks.

I worked at an Esso Avitat for a number of years, and before we could take delivery of a fresh load of fuel, we had to test to make sure that the proper amount of FSII was in the fuel.

Ask the fuel boy next time when he last checked for FSII in the fuel he is pumping into your plane. He should be able to supply you with the documentation that shows whether it is in it or not. We could.
You don't want to be doubling up on the "dose" because it is an alcohol, and is not good for fuel bladders,(if installed) causing leaks over time.

[Ref Plus 10]

I'm actually surprised at the number of fuellers who have no clue whether or not their fuel contains some form of FSII...there are also many Shell and Esso fuel trucks I have taken fuel from who did not have pre-blended FSII. Our AFM mandates the use of Prist (or some similar product) at all times, regardless of OAT, imagine the funny looks I get adding it in Central America. It lowers the gel or freezing point of fuel, and I believe it is also an anti-organism additive (I could be quite wrong), and as said before, should be added in the specified volume, as it is quite corrosive.

[NormS]

The main ingrident in the Prist brand of FSII is DEGMME or diethylene glycol monomethyl ether. When this stuff is mixed in with jet fuel it migrates to the small amount of water in jet fuel and lowers the water’s freezing point to -46 deg F. According to Tom Burr of Arrow Energy, it does this by actually surrounding the water molecule to keep it from freezing. It is important to note that FSII has to be added to the fuel while fueling and cannot be added afterwards. The reason for this is that FSII is heavier than fuel and will sink to the bottom of the tank and not mix in with the fuel you are trying to treat.

The brand Prist also has some biocidal and pesitcide properities. That means it can help kill bacterial growth in your fuel tanks. We all know that bacteria likes to grow in damp dark places. And nothing is as damp and dark as a fuel tank. DEGMME is a pesiticide, although the manufacturers of Prist say on their website that it has not be certified by the EPA as such (just a guess, but it is probably cost inhibitive).

http://www.askacfi.com/80/what-is-prist ... t-used.htm