As the advice is contradictory from both suppliers and standards I thought I'd post my own recent experience of fuel hose degradation and my conclusions in case its of any use to others.
In 2019 I replaced (most) of the hoses on my Spyder as the original ones were getting a bit old/brittle/shrunk at the joints and weeping although no obvious cracking. I was advised to use SAE R9 rated hose as I was told it is ethanol rated so that's what I used.
Fast forward 3.5 years and that R9 hose is already failing. The pipe has hardened and feels brittle and cracks are visible in the outer surface on bends although no actual leaks yet. At the time I replaced most of the pipes I was a little short so used a bit of R6 rated pipe that I believe was left over unused from the original build back in 2003-4. It came in the box of bits that came with the car and matched the pipes I removed that had survived 15 years of use although for the majority of that time it would have been using E5 rather than the current E10. That length of R6 pipe is still looking fine with no obvious signs of degradation.
Shocked that what I thought was the correct grade of hose degrading so soon I've read the actual text of SAE J30 and as far as I can tell there is little mention of ethanol tolerance in either R6 or R9. It seems to me that this standard is being misquoted/misused when these pipes are sold. I'm not sure if there is another standard that better deals with ethanol tolerance but I can't find one and all the pipes are marked with the SAE J30 reference and either R6 or R9. It seems the difference between R6 and R9 is actually more to do with pressure rating and vapour loss.
Trying to understand why the R6 hose I used seems to have coped okay so far I found that it had a brand name - "Codan". Looking at the manufacturers data I can see that Codan do sell hoses that they rate as suitable for ethanol which are lined with Viton (FKM) whereas the non ethanol hoses are simply NBR both are rated SAE J30-R9 however. But, the one I used isn't the Viton lined one but is still okay so it seems that even for the NBR hoses they are not all made equal.
So, my conclusions:
Ignore the SAE J30-R rating when choosing new hose. it will not tell you if the hose is ethanol tolerant in use.
If the hose is generic/unbranded avoid it as it will most likely be straight NBR rubber and won't last with E10 fuel.
Only buy hose from brands whose data sheets show that it is ethanol tolerant and explain how it is achieved (e.g. Viton lining or PTFE or suchlike)
Don't use suppliers who tell you R9 is fine for E10
From my searching I found three brands that seem to tick the boxes but not all hose from those brands is right so you need to also ensure you get the right spec from their range. These are Codan 3133 VKM; Gates Barricade and Cohline 2240 or alternatively you can go down the teflon/PTFE route but then you'll need specialist fittings and deep pockets. If the hose you are looking at is less than £15/m it is probably unsuitable. I found suitable hoses from these brands were all in the £15-25/m bracket for normal 5/16" 8mm that is typically used on fuel injection flow and return pipes.
In this picture you can see the cracked 3.5 year old R9 hose and the non cracked 20 year old (but in use for 3.5 years) Codan R6
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cracked 2018 R9.jpg [ 224.96 KiB | Viewed 2944 times ]
