I use only spiced oil, at all stages of the preparation : making the stage-1 and stage-2 sauce, pre-cooking the chicken, and making the final curry. As Kris Dhillon makes plain, a good curry requires an excess of oil which can then be poured off before the final dish is served; I then continually recycle this oil through subsequent base sauces, pre-cooked chicken and further curries, augmenting it with new oil (usually groundnut oil, but grapeseed oil if I have any) as and when required. But I wouldn't use chip oil in a million years !