The remainder is 1-5/8-1/4=8/8-5/8-2/8=1/8.
If the quantity of dressing was 24oz, then there would be 15oz of olive oil, 6oz of vinegar and 3oz of mixture, consisting of 1oz each of salt, pepper and sugar.
If the vinegar doubles we have 12oz of vinegar. The quantity of ingredients is 15oz of olive oil, 12oz of vinegar, and 2oz of mixture (no sugar) making 29oz altogether. The proportion of olive oil is therefore 15/29.