CREATE TABLE table_19909 ("Series Ep." TEXT, "Episode" FLOAT, "Segment A" TEXT, "Segment B" TEXT, "Segment C" TEXT, "Segment D" TEXT)

Which episode has segment D on custom motorcycle tanks?
SELECT MIN("Episode") FROM table_19909 WHERE "Segment D" = 'Custom Motorcycle Tanks'
SELECT MIN("Episode") FROM "table_19909" WHERE "Segment D" = 'Custom Motorcycle Tanks'