Oil leak

[drowe]

Finished diy oil change in '04 Explorer as I have before. Oil pan drain bolt tightened, new filter tightened and oil topped to manufacturer's specified level. Started engine to idle (which I normally don't do) before backing down from ramps. After backing down, lots of oil leaked out from underneath. Going to look further to see exactly where the leak is happening but wanted to see if anyone could advise possible causes of the leak. Thanks.

 

[TechGuru]

Are you sure the old oil filter gasket came off with the filter?

What filter are you using?

 

[LaneSplitter]

What TechGuru said is the most common problem. The old oil filter rubber gasket stays on the block and then when you screw in the new oil filter there are two gaskets (the old one plus the new one) and it'll leak oil.
Remove the filter and double check that you didn't install it with two gaskets.