I discovered that Viton return hose has one advantage that the braided hose does not, that is it is reusable! if for some reason you have to remove the return lines to an injector you simply pull off the Viton hose using a good tug up close to the injector nipples, and it comes off without having to cut it. And it can be stuck back on and it continues works fine, no sweat! I decided to swap a set of injectors on my engine while I was troubleshooting a nailing nose, so my Viton return lines have been off and back on with no leaks!

I want to see when two years from now if the stuff is weeping like the braided fuel lines. I always wanted to use teflon return lines on my 603 engine but I couldn't find anything that pushes on a hose barb, its all made for crimp fittings.

I do not find the small Viton hose dangerously soft like someone reported, but this is the injector fuel return hose that I am referring to, not any of the larger hoses. Using thin wall Viton for some of the larger hoses is likely to be an issue because it is indeed more flexible than regular hoses.
I suggest using regular hose material elsewhere on the engine and simply plan on replacing it when it starts to leak if you run B100 or similar.

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!