Facts or myths?

[ProfJohnL]

The subject of the Bio fuels and life of the fuel tank and other related problem has been discussed previously here and elsewhere. There is something to be concerned about with some older vehicles, but the issue of corrosion and compatibility of fuel lines has not arrived in anything like the tsunami predicted by some people.

 

[Buckman]

However I thought the OP was mainly about water forming in the tank due to the ethanol which could affect the smooth operation of the engine and not compatibility or corroding of fuel lines?

 

[Raywood]

The subject of the Bio fuels and life of the fuel tank and other related problem has been discussed previously here and elsewhere. There is something to be concerned about with some older vehicles, but the issue of corrosion and compatibility of fuel lines has not arrived in anything like the tsunami predicted by some people.

Our eldest daughter and her husband have a 1954 Anglia used for shows and meetings and that needs E5. Like most cars of that age it does a very low mileage so these problems would not be obvious now even if E10was used. They are very aware of the problems in the enthusiasts groups and it has had a lot of publicity, so perhaps that might save the day.

 

[ProfJohnL]

Just as an example of how small changes in the items fitted to your vehicle might affect MPG, an american web site TFL See

View: https://www.youtube.com/watch?v=YWHt_Vr1Ik8
) is condcuting a number of back to back MPG tests with the same vehicle but in different configurations. The latest one I have highlighted relates to side rear view mirrors on a RAM truck and how leaving them in towing mode rather than solo can make a big difference. I don't hold it up as scientifically accurate in terms of the actual numerical difference but it s a reasonable demonstration of the principles involved. But to be fair they do manage to eliminate a large number of factors by carefully planning the tests.

 

[Raywood]

Anything that affects the airflow will affect the MPG, but this might show the difference is more than you thought. Possibly we could save a few drops of fuel by dropping the big Milencos.

 

[ProfJohnL]

You asked for some facts.

In relation to these sections

Ethanol in fuel absorbs water vapour from the atmosphere and it quickly contaminates the fuel. The ethanol blended fuel we are forced to use in the UK absorbs moisture from the air faster in a partially filled tank than in a full tank, particularly if the car is not used daily.

The "quickly" in this section is misleading, yes the ethanol is hydroscopic but it can only grab moisture when it's exposed to moisture.

We should all know that fuel tanks have close fitting caps and some even allow a slight pressure build up . that means there isn't free and quick air exchange into the tank, and the reason is that both diesel and petrol both naturally vapourise and the vapour at normal air pressures and it's is heavier than air so your fuel tank rather than having an "air" cap actually has a vapour cap which excludes air. Even when refilling, a very small amount of air might try to enter when the filler cap is removed, but as you fill with liquid fuel, it will displace the vapour further excluding the entry of fresh air.

As you use a tank of fuel the void above the fuel grows, but its filled with fuel vapour it should not drag in external air.

Consequently the fuel in the tank is not exposed to copious amounts of humid air and thus the fuel will not "quickly" become contaminated.

The rate at which the fuel could become contaminated by air in the tank is not determined directly by how full or empty the tank is. It's basically governed by the exposed surface area of the fuel. Whilst the surface area may change a little at different levels in the tank, the change is not related to the depth of fuel in the tank. But.. The degree to which the content of the tank could be affected would be less for a fuller tank, but for the reasons given previously this is not a major accelerant to the problem as external air exchange is relatively small.

Basically the article is highlighting a potential real issue, but it is making a mountain out of a molehill and scaremongering. However it does not change the wider issue of trying to reduce bad emissions from motor vehicles.

 

[Buckman]

Thank you for a very informed and interesting post.