[T3] Is there a real issue with using 5/16" ID fuel hose ratedSAE 30 R7 ?

[Jim Adney]

Much of the problem here is that people tend to lump different kinds of 
elastomers together as "rubber." The author of the piece you cited does 
somewhat well at avoiding that trap, but not completely. If you take a look at 
the web sites of makers of O-rings or hose, you will find that there are at 
least a dozen different families of elastomers and each family has multitudes 
of members.

It's hard to believe that any major hose manufacturer would make fuel hose 
today that would not be compatable with large amounts of ethanol. 
Remember that Russ told us that his company, Mahle, switched to rubber 
seals that were compatable with E85 years ago. That doesn't mean that it 
would be impossible to come across hose that's been sitting in a warehouse 
for 20 years, or that came from a no-name manufacturer, but it's unlikely. 
Note that most hose also comes with dating printed on it.

I recommend Parker for their web site, but for a really good idea about the 
range of elastomers out there, find a Parker O-ring catalog. I stock a Parker 
fuel hose which has worked well for me in the 5/16" size. I used to get 
Airequip hose, but they discontinued the version that I liked. Both were 
good, but I have to buy it in 100' coils to get a decent price. I sell it for $3/ft 
or 22' for $60 plus shipping. (22' will do a full '70-3 FI car; '68-9 takes a little 
less.)

One place where the cited text goes wrong is with Tygon. Tygon makes 
dozens of different kinds of excellent, mostly low pressure, hose, each in a 
variety of sizes. Only a couple of them are compatable with fuel; those are 
all yellowish. I use those in my overflow hose repair kits and they have 
worked great. Other varieties of Tygon will work with fuel for short times, 
then turn hard and eventually crack. That's not a Tygon problem; it's a user 
problem because the user chose the wrong kind of hose.

I don't think there is a Tygon hose suitable for 30 psi gasoline or gasohol.

So the short answer is that you have to make sure that you're buying FUEL 
hose. Water hose won't hold up, and hose for brake fluid is different from 
both of those. And it's also important to pay attention to the minimum bend 
radius that the hose is rated for; this can vary a lot.

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Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA
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