Yes, I'm familiar with the concept of gain and loss basis when converted to business use.  But I am still not sure how to allocate the basis between business and personal use.

The real question is for determining the gain basis should the lifetime miles of the vehicle be used or should only the miles driven since the first business use be used as the denominator.

In the present case, if we only choose to use the miles after the first business use we would have 29% (6335/22016) Business use.  If we assume that the FMV of the auto at conversion was $6500, this would give us a loss basis of $696 (29% x 6500) less 1174) and a gain basis of $5156 (29% x 22,000 less 1174) with the proceeds $1,870 resulting in no gain or loss.