If it were meant to be straight and was now curved, there would have to be another bend or damage somewhere else to compensate for the longer path between downtube and dropout. Besides, most unintentional bends leave a crimp in the tube or damage the paint. An inward bend would make far more sense than an outward bend if it resulted from an accident. Good chance the bike was made with that curved tube.
Oil is good, grease is better.
2007 Peter Mooney w/S&S couplers/Terry Butterfly
1993 Bridgestone MB-3/Avocet O2 Air 40W
1980 Columbus Frame with 1970 Campy parts
1954 Raleigh 3-speed/Brooks B72