E10 fuel and the T3

The consensus seems to be that it won't be an issue for the engines - many countries are already running on E10 anyway, and there haven't been any big problems reported for T3s.

However, as chris7ian says, the main thing you have to watch out for is your fuel hoses. If you haven't changed them recently then I would suggest you do this immediately, as they perish as they oxidise over time, and the ethanol content in the fuel can acelerate this process. This causes cracking of the rubber in the hoses, which can lead to fuel leaks in the engine bay, and possible fires. Brickwerks have a really detailed article on their blog about the the problem with buying suitable fuel hose, which is here:

To paraphrase, you need to check what you're buying, and the suggestion is that you make sure that any new fuel hose you buy is compatible with 100% ethanol, i.e. E100. Neither the R9 spec (SAE J30 R9) nor the R14 spec (SAE J30 R14), both of which you frequently see quoted for fuel hoses, require compliance with an ethanol content higher than 5%, so you need to look for a hose that not only meets either the R9 or R14 spec generally, but which also exceeds it in respect of Ethanol or Biodiesel content. The hose that Brickwerks sell is R9 spec plus compatability with fuel that has up to 100% Ethanol or Biodiesel content, and products like the Gates Barricade hoses are similar, so I would suggest going with something like that. Whatever you do, don't just buy generic R9 or R14 hoses off the interweb and assume it will be okay.