Re: [FWDLK] Octane

[David Homstad <dhomstad@xxxxxxxxxxx>]

Tony,

While Neil's D500 may run OK with 87 octane at 4000 ft altitude where the
lower atmospheric pressure lowers the combustion chamber pressures, any
engine over 9:1 compression should seriously consider 92+ octane. Especially
if you have improved upon the extremely conservative ignition advance curve
the 56/57 D500s had. Those are already retarded 10 degrees compared to a
315/325 Poly (C/R 8.0) because of their compression ratio.

The reason premium fuel gets better gas mileage is that you can run the
engine with more ignition advance, which is more efficient. If you have to
retard the ignition advance to use 87 gas, you will spend more money because
of an improperly tuned engine than you save on gas. But using more octane
than the engine needs is also a waste of octane and money.

You might try 87 gas, but don't fill the tank over 1/2. Leave room to add
some of that 110 gas if the engine pings under acceleration, especially on a
hot day.

Gas for different brands may all come out of the same pipeline, but the
additives can make a big difference. Just like soda pop, the water may come
out of the same faucet, but the flavoring additives makes all the
difference.

Dave Homstad
56 Dodge D500

-----Original Message-----
From: Forward Look Mopar Discussion List
[mailto:L-FORWARDLOOK@xxxxxxxxxxxxx]On Behalf Of eastern sierra Adj
Services
Sent: Monday, August 25, 2008 11:24 AM
To: L-FORWARDLOOK@xxxxxxxxxxxxx
Subject: Re: [FWDLK] Octane


I routinely install regular grade gas in my car (87 octane) , also a 57
D500 with 9.25 :1 combustion ratio, year round here, at 4K' elevation,
without any apparent adverse reactions.

You can adjust your car's timing to the gas grade, and just don't try to
do anything dumb, while using the lower octane.

Name brand gas does have more-better additives than the discount brands,
but the base-gas is all the same chemical substance; when the tanker
pulls up to the refinery, or wherever it gets its gas, the attendant
figures out what brand/type of product the tanker is supposed to
receive, and, just like the way your local hardware store mixes up
paint-to-order
colors, the attendant adjusts some valves and differering quantities of
additives are added to
the base gas, to produce "Shell", or "Texaco" or "CitiesSevice", or
BumFart blended gasoline.

It is claimed that higher octane might produce better MPG, but,
gas-is-gas ; the difference between the commercial products is the
quantity and quality of the additives which are put into the gasoline.

Neil Vedder

-----Original Message-----
From: Forward Look Mopar Discussion List
[mailto:L-FORWARDLOOK@xxxxxxxxxxxxx]On Behalf Of Anthony C. Boatman
Sent: Monday, August 25, 2008 10:58 AM
To: L-FORWARDLOOK@xxxxxxxxxxxxx
Subject: [FWDLK] Octane


Hi All,

I have a 57 Dodge with the D-500 Hemi engine in it, and I've been using
Unleaded Premium with a 93 octane rating.  It runs just fine, but I'm
wondering if I am spending extra $$ I don't need to.  Should it run equally
well with lower octane?  Considering I drive it about 200 miles a year at
most, I guess it doesn't really matter, but is higher octane really better
for this engine?

A local station has begun carrying 110 octane, and some have suggested I
even switch to that.  Since I've never driven the car faster than 65 mph
that I can remember, it's not like I need any more power.

Thanks,

Tony Boatman
57 Dodge D-500

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