I believe petroleum is the best.

Petroleum is not a bad thing in water where sulphate of lime prevails; but you should use only the refined, as crude oil sometimes helps to form a very injurious scale.

After coal, petroleum is the most important item, and in 1902 nearly 57,000,000 gallons was refined and sold in the India market, but this was not sufficient to meet half the demand, and about 81,000,000 gallons was imported from the United States and Russia.