7 replies to this topic

[Java_Green]

Why do you need to treat a full tank when you are about to treat petrol? Is not it better to just leave a little petrol in the tank and treat that quantity? I am refering to a classic vehicle that is garaged in a tempered garage over the winter.

[Spider]

The thinking there is with less air space, some of the volatile components are less likely to evaporate out of the fuel.

I'm no chemist, but sounds plausible to me.

This might also be helpful

 

 

[StefanMini]

https://youtu.be/yXR..._p_K7Q0L7FGkTfS

[slidehammer]

The other thing that contributes the the issue, is Ethanol absorbs moisture which makes the fuel less volatile. So if the tank is stored with less fuel in there is the possibility of condensation forming on the upper part of the metal tank which then would drip into the fuel in the form of water, filled right up it is less likely to happen. I store my vehicles full and with Sta-bile in the tanks and it seems to help. I know AC Dodd uses it and has also shown the damage Ethanol does to carb needles in his Youtube videos

[alpder]

Any air left in the tank will expand and shrink - most especially due to day/night temperatures but also changes in barometric pressure. This means that the tank slowly sucks air in during the night (as the air inside the tank cools and shrinks). This new air cools inside the tank and so loses its moisture either into the ethanol or as condensation on the inner tank walls. Then the (newly dried) air gets slowly blown out during the day (because the air in the tank warms and expands). Ready for new, damp air to be sucked in the next night. So, gradually, the tank accumulates water that has condensed out of the surrounding air.

 

The less air in the tank, the less air is exchanged in the day/night cycle, so the less water ends up in the bottom of your tank at the end of the winter.

 

Unfortunately, to prevent this means filling the tank with (modern) fuel. Which contains ethanol and therefore lurves water. I try to fill with Super (which in my part of the UK has zero ethanol edit: I am reliably informed this is no longer true) at the end of the summer. And during the summer I use E10 but add Valvemaster whenever the fuel is going to be in the tank longer than a couple of days.

Edited by alpder, 16 August 2024 - 06:28 PM.

[Chris1275gt]

Any air left in the tank will expand and shrink - most especially due to day/night temperatures but also changes in barometric pressure. This means that the tank slowly sucks air in during the night (as the air inside the tank cools and shrinks). This new air cools inside the tank and so loses its moisture either into the ethanol or as condensation on the inner tank walls. Then the (newly dried) air gets slowly blown out during the day (because the air in the tank warms and expands). Ready for new, damp air to be sucked in the next night. So, gradually, the tank accumulates water that has condensed out of the surrounding air.
 
The less air in the tank, the less air is exchanged in the day/night cycle, so the less water ends up in the bottom of your tank at the end of the winter.
 
Unfortunately, to prevent this means filling the tank with (modern) fuel. Which contains ethanol and therefore lurves water. I try to fill with Super (which in my part of the UK has zero ethanol) at the end of the summer. And during the summer I use E10 but add Valvemaster whenever the fuel is going to be in the tank longer than a couple of days.

As of September 2023 Esso 99 super has contained ethanol up to 5% country wide

[alpder]

As of September 2023 Esso 99 super has contained ethanol up to 5% country wide

 

:-( Even so, a full tank of E5 with stabiliser should still be better than a tank full of air, for winter storage. The trouble being you end up with a nice rust-free tank... full of aged fuel.

 

Does anyone know if Sta-Bil is different to other products (like Valvemaster). Both say they stabilise the ethanol content. Which should be enough for a car that's in reasonably frequent use. Sta-Bil's blurb suggests it does more to stop the fuel aging but without actually saying what... So are they the same? Or should we be using Sta-Bil for fuel stored over-winter? I'm sure that's what their marketing team would like us to do.

[alpder]

So, yesterday evening I sent a (slightly tongue-in-cheek) question to Valvemaster. Really not expecting a reply. Was pleasantly surprised to find a patiently scripted answer in my inbox this morning.

 

Here's my question:

 

I've been prompted to ask the following by a discussion on a UK classic car BB. There is a sense that Sta-Bil (boooo, hissss) is better than Valvemaster for long-term fuel stability. Or is this just Sta-Bil's marketing BS working its magic? So, I wonder if you could tell me...

Is Valvemaster as good at stabilising E5/E10 as Sta-Bil? Sta-Bil's marketing says that it makes petrol stable for months. By comparison, how long can petrol treated with Valvemaster be stored before it degrades - not just the ethanol content but also the volatiles? Will Sta-Bil do a better job? Does it make a difference if the tank is vented (car fuel tank) or unvented (jerry-can)? Does it make a difference if the air/fuel interface at the top of a vented tank is minimised (e.g. by topping-off right up into the filler neck)?

Looking forward to your comments.
Kind regards,
Ian.

 

And here is their reply which, while it doesn't answer all my pesky questions, is still clearly not a cut'n'paste job so kudos to them for bothering:

 

Good Morning Ian, thank you for your email.

 

The Valvemaster range contain a blend of chemicals under the name of Etha-Guard.  The primary purpose of Etha-Guard is to stabilise ethanol blend petrol under running and storage conditions.  I understand from the Sta-Bil website that they claim ‘up to 24 month protection’.  It would feasibly be possible for both products to provide protection for this long under ideal conditions - ie. in a laboratory.  For Etha-Guard we only say 6-12 months, as the intended storage application is over winter.  For longer term storage we would recommend draining.  It is best that the tank/container is full to minimise the air gap at the top, reducing oxidation.

 

It is not possible to give you a direct comparison, or test the longer term claims, as the chemical content on their msds is withheld as proprietary.  However, regarding your questions below raises two key questions:

1. How do the products compare re. water absorption and phase separation?
2. How do they compare on fuel degradation? 

1. Etha-Guard utilises Hydrocarbons (C10 arom.) and 2,2’-iminodiethanol.  The hydrocarbons act as solvents to maintain homogeneity, reducing the chance of phase separation.  The 2,2’-iminodiethanol absorbs and neutralises any water in the fuel.  The Ethylene glycol monobutyl in Sta-Bil is the solvent that they use.
2. Sta-Bil list Napthalene, which is a preservative, and likely other additives in the proprietary blend that will reduce oxidation.  Etha-Guard contains Napthalene as well as Cycloheyldimethylamin and Amides (C16-18, C18-unsatd.).  The cycloheyldimethylamin prevents oxidation of the fuel, and the amides stabilise it by forming a protective barrier against oxygen.  The hydrocarbons C10 mentioned in 1) also prevent the evaporation of lighter hydrocarbons in the fuel.

Both products therefore will be effective at stabilising fuel against water and preventing degradation from contact with oxygen.  Etha-Guard also has a component that explicitly prevents evaporation of the lighter volatiles, Sta-Bil list petroleum distillates and proprietary ingredients for this purpose.

 

In summary it is therefore not clear cut.  We do not make a claim for 24 month performance as our product is tested and marketed for over-winter storage.  Sta-Bil may well have tested their product for longer periods, we would recommend draining the tank for long term storage.  Storage conditions for most vehicles are usually far from ideal!  I hope that helps you.

 

Kind regards,

Dan