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As I was putting gas in my vehicle yesterday, I began to wonder if Pre-War Packs run better on high octane gas.

thank you
Garrett Meadows

87 octane gas we have today is higher octane than what they typically had available when your car was new.

The low compression pre-war engines don't need a higher octane to run well, but some markets you can get ethanol free gas in the higher octanes, which, in my opinion, runs better.

56 Cushman owned and ridden for 34 years at least 500 miles/year. CR about 6:1. 48 indian owned and ridden every year for 40+ years at least 2K miles /year. 6:1 CR. Runs EXTREMELY hot by nature. Various Ag equipment from 1950's operated every year for over 20 years. Other vehicles of the past.
They ALL run much better on the higher octane modern fuel.

Mostly i only run the hi-octane in the motorcycles. But can definately tell a difference (most of the time if the gas station didn't dump cheap stuff in for higher priced octane a common practice) on the bikes.

Car engines tend to run cooler so the low octane mite be ok. The high octane definately will not hurt any engine. I have too many miles and too many years t o prove it on the SAMEE equipment.

The Indian WILL spark knock on the low octane despite it's 6:1 CR and no i'm not running any hot rod engine parts other than Carrillo rods. The spark knock is rather subtle but i am sitting right ON TOP of the engine and can hear it. No spark knock wwith the high octane.

Low speed operation the low octane is ok. Moderate to High demand engine operation i recommend using the HIGH octane.

Or just experiment with it yourself.

We blew up a garden tractor once running it on 100 octane avgas. Guess that was too much of a good thing for it.

It depends on what you have. The postwar owner's manuals have the recommendations. For example, the higher compression straight eights and the V-8 should be using premium. The straight eights are prone to carbon build up and the 54 manual recommends premium. The 22nd series recommends regular.

I had a problem passing inspection with my modern car when I was in Pentagon City VA. I had been running regular and had some carbon build up. Since then I have been using mid-range.

Running higher octane in Packards is expensive because they gulp gas, but piston wear is more expensive.

A common myth is that old gasoline was junk. Actually back around 1900 the gasoline was pretty darn good. It wasn't until demand outstripped supplies that they needed anti-knock compounds. Today's car run on regular because the computer controls prevent detonation.

Quote from post #7 above:
" Today's car run on regular because the
computer controls prevent detonation."

PRECISELY!!! and explains the gasoline debate exhaustively.

The "clear gas" non-oxygenated fuel at the Mobil near me is what I use in the '54 Clipper when I can. If I recall correctly, it's 92 octane. I've also used it in my mower and snow blower for years.

This fall, topping up the tank before storage I goofed up. The "clear gas" and "racing gas" pumps are next to each other and... well 2 gallons of 110 octane "racing gas" was in the tank before I noticed the pump already read almost $20. THAT'S not right! (Racers are a different breed. Money is no object.)

Switching to the other pump for the last two gallons, I then had a top-off of half-and-half. I'm not too worried about it. The rest of the gas in the tank was mostly regular "clear", which goes for about $5 a gallon. Car runs just fine on it, although when I've used "oxygenated" gas with alcohol on the road I haven't really noticed a difference. It seems like I get slightly lower mileage, but really no way to test it because I usually fill up when the tank is still about 1/3 full.

Both of the pumps said: "Not a Mobil blended gasoline" so I don't know what's up with that. Maybe they buy it on the black market. Bottom line, they stock the "clear gas" specifically for cars from the pre-no-lead days and off-road use engines. I always feel a little better using it, and they probably feel better getting the extra money.

When all is said and done, I'm usually running a mysterious mixture of gasoline types and additives. (I put a little "Startron" stabilizer and supposed alcohol-destroyer in it when I get a substantial fill of alcoholic gas--once again, mostly a feel-good thing--and a dash of MM oil every so often.)

Given the choice, I always use the non-oxygenated stuff. There's even a website (of course) for finding it. I have no idea how accurate or up-to-date it is, but see if you can find a station near you!

pure-gas.org/

Some other things to keep in mind... While a given engine's "static" compression ratio from the factory may be 8:1... ...depending upon the camshaft's valve timing (opening and closing) that could lower the dynamic compression ratio to 7:1. A compression test usually tells the tale. ...and then the ignition timing, if delayed, could lower that. Remember all of those 1970's big blocks that had 10.5:1 compression one year, and 8.5:1 the next year. One of the things that they did was to delay the cam gear by 4 or 8 degrees. ...and then ignition timing was delayed a bit, and topped out at 24 degrees or so, when they topped out at 34degrees a year earlier.

Mark