As I just mentioned, my injector return lines are seriously bleeding fuel now, thanks to more fuel getting to the engine through some new filters. However, I have visited 4 different auto parts stores to find some 1/8" I.D. (inside diameter) fuel line to replace it with. No one has it, and all I get is confused looks.
I shouldn't say no one, because Advance Auto does have 1/8" fuel hose (for chainsaws) in 2' sections ($1 a foot) that I tried. It technically works, but it worked practically work. For one thing, its clear PVC hose that will probably not last too long against diesel fuel, and also it won't actually go onto the hose fittings. The hose is too thin and flimsy to fit over the barbs on the hose attachment points. I got one section on with that and its working, but I think that I will go with a solution designed for this purpose.
The best (and cheapest) source I have found for these hoses is online. Greaseworks.org is a biodiesel/veg oil conversion website that carries hoses and other misc. parts for these Mercedes.
They have a specific kit for this replacement ($30 shipped) and its also biodiesel resistant so if I ever decide to start pouring soybean oil into the tank, it won't eat these hoses up (just all the other hoses). Okay, so I'm not converting my car to biodiesel, or veg oil, but I'm not ruling it out especially if diesel fuel keeps creeping up in price.
When I bought this car (5 months or so ago), diesel was cheaper than regular unleaded here at the local truck stops. Now, its more than premium unleaded. This is very annoying. Hopefully I will get that extra fuel mileage I've been hoping for once I have all this maintenance taken care of.
Also, my fuel treatment experiment is officially over. I tried Startron fungicide and Marvel Mystery Oil in it for about four tanks and didn't see much in the way of mileage increase. However, I think the startron might have loosened some stuff up and caused the fuel filter to get clogged.
Maybe, just maybe I'll see a large fuel mileage jump with this next tank of fuel now that the filters are new, and the injector return lines aren't spilling $3.11/gallon out all over my engine.