I have for a long time used TetraBoost (the latest mix is called EGuard15) in my older vehicles (Lotus Elan/MGB GT).
Its makers state: "TetraBOOST contains anti-acid formulations designed to minimise the problems associated with ethanol water absorbtion and acid formulation – unbeatable both for regular driving use and over-wintering situations"
It contains tetraethyl lead in solution and increases octane levels. It is NOT suitable for vehicles fitted with catalytic converters or permanently-mounted 02 sensors. However, later cars with cats etc are unlikely (as has already been stated) to suffer from ethanol in the fuel anyway.
I find mixed with super unleaded, Tetraboost (I have no connection with this product except as a customer) allows more aggressive timing curves without pre-ignition and commensurate increases in power and efficiency.
But, over winter, there's no substitute for (on a dry day) a really hard run for at least ten miles with enthusiastic use of brakes (to free up those pesky Morgan rear slave cylinders). Not much chance of that today -- it's snowing even in Cornwall!
