The only effect of temperature is to increase the sensible heat content of the oil. The specific heats of oils are publicly available, and approximate 2.2 kJ/kg..

nothing. temperature of flame in burning has relation to BTU, but you can store diesel fuel at any temperature, it's BTU will stay stable (within reasonable storage conditions)

But there will be sensitive difference in temperature by burning diesel fuel at different temperature of dosing, just like there is a difference between lower and higher heat contents.

I was more referring to fuel Supply temperatures for a large diesel generator - was I loosing power if the fuel supply temperature increased for 30C to 70C