How does the octane rating of today's gasolines compare with the rating requirements from the 1960s? If the Owner's Manual says to use minimum 92 Octane, what should be used now? What factors other than octane need to be considered? My understanding is that the lack of lead is not a concern unless the engine is often run hard--as in racing. Is that correct? Engine in question is an original 170 cid SIX in a 1965 Falcon with C4 tranny.