We already knew about a classic unleaded (green) gasoline with an octane rating of 93 being rolled out in 1993 until present at all gasoline stations. The cost was only 2% to 3% lower than the now defunct premium leaded gasoline with octane rating of 93 and the present trademark of high performance unleaded gasoline with a variant of 95 to 97 octane rating. Of course, some drivers had been confident to use that gasoline at an affordable price in spite of limited engine performance.
But now an unleaded (green) gasoline has now degraded from octane rating of 93 down to octane rating of 91 on some gasoline stations in the Philippines such as Petron “Super Extra Gasoline” in 2nd quarter of 2013 and recently Shell “Fuel Save” Unleaded in October 2013. Why? Not only such aforementioned gasoline stations have had addressed to develop an affordable gasoline formulation in order to lower the cost from original 93 octane rating of classic unleaded gasoline by 0.5%, but also claimed to lower emission levels and increase fuel efficiency in spite of limited engine acceleration than that of 93 octane rating counterpart.
So what is the main difference between the classic 93 octane rating and the 2013 formulation 91 octane rating of unleaded (green) gasoline? We often thought that being an octane rating of 91, although work well on ordinary gasoline engine, would easily damage some earlier high performance engine that requires a standard gasoline formulation with a minimum octane rating of 93. In order to reduce such problem the 2013 formulation version unleaded (green) gasoline with 91 octane rating consisting of a special formulation that often “coat” the entire cylinder piston to become a special protective film before ignition stage may prevent engine knockdown. Therefore it would become the same engine protection measure as that of classic 93 octane rating unleaded (green) gasoline.
It’s so technical to inform the comparison between the classic 93 octane rating and the 91 octane rating 2013 formulation version unleaded (green) gasoline, even though the development remains confidential. Before the new 91 octane rating unleaded gasoline formula was introduced in 2013, a few years ago competing gasoline companies like Shell based in Europe and Petron based in Philippines have had distantly developed a fuel efficiency formulation and apply to their own 93 octane rating unleaded (green) gasoline.