im not sure about the whole gap issue. sure a bigger gap is safer so you dont hit the car in front. but in busy traffic too much of a gap just offers up people to try and squeeze between you and the car in front which puts you right on that second cars bumper. i have that happen all the time, i dont want to tailgate someone but i also dont want a car thinking they have room to enter the lane in front of me if i leave a bigger gap.
as for the crash i have no idea the cash. but i doubt it was oil i think either you grabbed to much brake. or seeing the car in front getting closer while hard ont he brakes you tried to turn(probally without even knowing it) and lost the front wheel that way. no thing you could have done about other than hang back a little.
guess its just a matter of feeling the traffic out if a car next to you seems to be trying to get in your lane slow up and let them in creating enough of a gap behind them. or speed up and hold your lane position while staying closer to the car in front.