Tom,
Did not jump to a conclusion, just been there with a car which sat (garaged) for 5 years. In Ca. the condensation might be void, but here in a humid at times NJ, the tank had to be replaced. I did not replace it initially, ( thought I might get away with the additive) 200 miles and two tows, I pulled the tank and cut my losses.

I did not consider the location when originally writing the thread. But I still would not hesitate to pull the tank, It is no be deal.
Just two approaches.
We buy these cars to work on them do we not ????

__________________
Gary
Experience is something you get, Just after you needed it....
'99 E300 295K, '83 300D 220K, '75 240D 185K sold
'80 MCI Bus Conv DD 6V92TA, w/4 cyl. Kubota diesel GenSet 12.5KW