Since we want the engine to warm up faster so we can be in S2/S4 sooner, have people noticed some brands burning hotter than others due to the additives they employ. I seemed to be able to employ P&G more often with Shell's "nitrogen-enriched" fuels but I am not sure if it's that or my fluctuating driving style.
I'd guess the fluctuating driving style and fluctuating morning temperatures have a lot more to do with it. There would be a lot of environmental factors that would outweigh gas additives for heating the engine up. You can try a partial grill block using insulation foam to speed the process along (limits cool air hitting the radiator and the engine bay). If you have a scan gauge, it helps a lot to see how your water temperature is doing.
