I would add that perhaps the best answer here would be that it depends today on the chemistry of the fuel in your local market. If you live in an air quality management district or have low octane numbers or ethanol percentages or "smog" fuels of some type, chances are that "regular" is not going to be adequate for your original compression ratio hemi motor. It would have been originally, but it may not be today. I would suggest using mid-range fuel as a rule unless you wish to study the octane and other content stickers everywhere you travel and fill up. To some degree, it is also going to depend on timing of your engine, specifications of your camshaft, what jetting is in your carburetors and etc. as well. In lesser states of tune, or in higher performance conditions, premium would either be totally wasted or absolutely required! Wayne -------------------------------------------------------------------------------- Date: Fri, 15 Jul 2005 23:10:09 EDT From: eqrode@xxxxxxx Subject: 392ci Fuel What is the proper octane fuel for the 392ci 375 HP? (1957 300C engine) Can anyone shoot me a quick response? Ed Rode [Non-text portions of this message have been removed] To send a message to this group, send an email to: Chrysler300@xxxxxxxxxxxxxxx For list server instructions, go to http://www.chrysler300club.com/yahoolist/inst.htm Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Chrysler300/ <*> To unsubscribe from this group, send an email to: Chrysler300-unsubscribe@xxxxxxxxxxxxxxx <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/