Higher octane fuel will not help lower HC; it will cause fuel to burn slower and cooler. Advancing timing might lower HC, however you are allowed only +/- 3 degrees, so you want to ensure you don't fail the timing functional inspection.
Our recommendation would be to investigate why you have high EGR flow, and to also ensure your Ranger's computer is in proper fuel control. You can start by making sure the oxygen sensor is functioning properly, and CO levels are within the normal range. Both high or low CO emissions will cause high HC.
posted by SmogTips Support
