Please please please understand that im not trying to be a jackass, but its not diesel fuel leaking is it? All the fluids in a car have a unique smell to them, but im not 100% sure which smells like wd40, Clear and oily, diesel, brakefluid, could be biodiesel, which doesnt smell like diesel at all,

Wont be ATF, it may be coolant which can feel oily sometimes, certainly not oil.

My sugestion, if its not obvious which fluid it is, smell the brake fluid and coolant, and the fuel tank, see which is closest, Fuel leaks are common on diesels.

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1984 Euro 300SDC, (4spd standard)
1986 Toyota Landcruiser Diesel HJ60 5spd X2

Gone but not forgotten (some sold, some stripped)
1983 300 SD, 1985 300 SD, 1983 240D, 1986 300 SDL, 1985 300 SDL, 1983 300 D, 1984 300 D, 1985 300SD, 1987 300 SDL, 1983 300 SD, 1985 300 TD Euro, 1983 380SEC, 1990 300 D, 1987 300D, 1982 300D, 1982 300D, 1994 E420, 1987 300 TD, 1987 300 D, 1984 300 D