93 octane fuel

Shouldn't need that high an octane fuel unless you are running a high compression ratio. But to high an octane shouldn't cause a driving issue. How about bad fuel? I have seen several cases where the fuel (at the supple station) is contaminated with something, like diesel or water, etc.
 
The chugg description will need further clarification. At what rpm is this chug and is it when the engine is under load or no? Engines will miss and rpm fluctuations can happen under certain conditions but the only thing that chugs is a steam engine in my way of thinking. Stuck valves can cause after fire in the exhaust and a lean fuel mixture can cause backfire through the carburetor. These would be like the definition of "chug" when related to motor vehicles.
 
The question, as asked, cannot be answered. Please define what "chugg" means? Running octane much higher than the requirements of the engine can cause some performance issues but I would not refer to that as being a "chugg".
 
Higher octane fuel burns slower than a lower octane number. Higher compression ratios require a slower burn rate than lower compression ratios. Did the engine "chug" before you tried the 93 Octane fuel?
 
warhorseracing said:
Higher octane fuel burns slower than a lower octane number. Higher compression ratios require a slower burn rate than lower compression ratios. Did the engine "chug" before you tried the 93 Octane fuel?
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Higher octane fuel has more resistance to pre-ignition, it is more resistant to ignite due to compression. In a gasoline engine you want the fuel ignition to be by the spark plugs.

It doesn't have any more energy or higher performance. In a flathead it is a waste of money.
 
mrtexas said:
Higher octane fuel has more resistance to pre-ignition, it is more resistant to ignite due to compression. In a gasoline engine you want the fuel ignition to be by the spark plugs.

It doesn't have any more energy or higher performance. In a flathead it is a waste of money.
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That is what the slow burn of higher octane does is slow down the ignition rate to burn slower. Exactly, a waste in any flathead unless running extreme compression or forced induction. Even then it depends on the timing and static compression ratio.
 
I run non ethanol fuel which only comes in 93 octane in my area, no problems in my ‘41 or the snow blower, lawnmower.
 
marko39 said:
It sure makes my 40 year old chain saw start easier and run better.
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My impression and my friends who have used higher octane gas in a variety of vintage vehicles is the car runs better -However its probably pyschological rather than scientific . The same pyschology that gets millions adding useless fuel additives to the gas tank.
 
Karl said:
My impression and my friends who have used higher octane gas in a variety of vintage vehicles is the car runs better -However its probably pyschological rather than scientific . The same pyschology that gets millions adding useless fuel additives to the gas tank.
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I think he is referring to non-ethanol gas. I agree 100%. The ethanol gas causes havoc in small engines and motorcycles if left to sit for any extended period; even with Sta-bil, etc. in it.
 
Karl said:
My impression and my friends who have used higher octane gas in a variety of vintage vehicles is the car runs better -However its probably pyschological rather than scientific . The same pyschology that gets millions adding useless fuel additives to the gas tank.
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When my dad was growing up in SE Massachusetts in the '30s, they lived behind his stepdad's gas station on rt 6. They sold something like 8 brands of gasoline. Flying A, Mobilgas etc and the loyal customers would swear by their particular favorite brand of gas... "ol Bessie won't even climb a hill on the cheapass stuff you're filling up on". Well, years later Dad told me they only had One underground tank and it was re-filled at night by a flat black painted fuel truck...
 
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