Originally Posted By: gathermewool
Is it a ECU thing or a materials thing. I know I've read of high HP, FI guys being tuned for E85, which is much less prone to det than E10, IIRC
Both. Fuel lines must be upgraded because E85 can damage them. Also, the vehicle must be able to adjust for very different octane levels. This is done in different ways, but I don't know enough on the technical ways to really explain them. From what I have gathered, essentially the whole fuel system is upgraded. Every parts store lists the flex fuel model Ranger as a completely different engine when you select your vehicle in the computer system, so I would say there are some significant differences.
That said, I remember reading a web page with pics about a '98-'99 Tahoe, non-FFV, that was run on E85 for something like 100,000 miles. IIRC, it had some occasional drivability issues, but no major problems.