Hugh, I get 13.6-14.9 mpg on the highway at 70 mph depending on the terrain. To my knowledge the engine has never been apart. I do suspect carbon buildup as the culprit in enhancing the ping. See my previous post concerning the lengths I have gone with timing, plugs, chassis dyno etc. Someday when I rebuild the engine, I will use the 1957 9.25 to 1 compression pistons to rectify the situation permanantly. >From: "hugh hemphill" <hugtrees@xxxxxxxx> >Reply-To: mailing-list@xxxxxxxxxxxxxxxx >To: <mailing-list@xxxxxxxxxxxxxxxx> >Subject: IML: need 94 octane in a 58 Imp ? >Date: Mon, 25 Feb 2002 19:59:23 -0600 > >From: "Robert Dervin" <rjdervin@xxxxxxxxxxx> > > > > I need to run 94 octane in my '58 along with a bottle of booster just to > > keep the ping out. That is with only 6 degrees BTC initial and only 19 > > degrees total advance. Other added advantages to premium fuels are >better > > detergent, more consistancy and smoother running. > > >This is a thread that can go on ad infinitum if not ad nauseam. I am >interested to know what kind of MPG you are getting on this car with the >current engine set up. It seems to me there is no such thing as premium >fuel. It is all the same stuff, only the plus and the supreme have >additional additives. The latent power is exactly the same. the additives >serve to provide a higher resistance to knocking or pinging and that's it. >I have never heard of detergent in gasoline, but that does not mean much. > >I dare to suggest that few people with these engines have to go to the >lengths you are going to, Bob, to avoid knock. I certainly do not have to >do anything like it, and, as admitted, having been educated in frugality by >the Scottish education system and culture, I run 89 octane in mine. >Dimitrios tried to show me the benefits of running higher octane gas in the >engine with the timing advanced, but I found it to be very unsatisfactory, >and was glad to get the backing of engineering reports published in 1958 to >provide quantified, objective, analysis on the subject. Objective in as >much the report was not created at the behest of either the car or the oil >industry. > >I suspect, Bob, your engine has some significant issues for which the use >of >the knock suppressing gasoline is only a band-aid. That is why I am >interested in your MPG. I am using rough estimates, because my odometer >does not work, but I am running at 16 to 17 MPG on the highway in my '58. >Stop start traffic kills MPG in the car. It really is scary seeing the >needle drop as I crawl along in crowded situations. But, out on the open >road, the car runs quite parsimoniously. > >Hugh >58 Imperial > > >