I use a two handled wok and only cook bhajis, pakoras, onions and peppers in the oil and then use the oil from the wok to cook my curries. If the recipe calls for 2 TBSP of veg oil i only use 1 TBSP of the spiced oil and get very good results, if a dish requires to be oily then i add extra spiced oil to my liking.
I have cooked a curry with oil used from cooking chips in and was quite disgusting very acidic (has somebody mentioned before) so i always keep my oils seperate, have been using the same oil now for about 3 months and the taste gets better and better. I sometimes add half and half ( recipe requires 2 TBSP i then add 1 TBSP of veg oil and 1 TBSP of the spiced oil).