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Why Shouldn't I use Premium Gasoline?


Justin Smith's Avatar
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04-30-14, 08:39 PM   #1  
Why Shouldn't I use Premium Gasoline?

For the past year of so, I've been buying premium gasoline for my small engines, as it seems to last longer. I had to open the owners manual to my old Generac 4000EXL gasoline generator to find the oil filter number, and it read:
Use regular UNLEADED gasoline with the generator
engine. Do Not use premium gasoline. Do Not mix oil
with gasoline.
What is the reasoning behind this? Now I don't know too much about engines, but if it runs better and longer it must be better, right?

 
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04-30-14, 08:45 PM   #2  
The mfg has probably determined that the small engine doesn't need the high octane, or that it may make it harder to start, or they may feel that it will generate extra heat that may eventually damage an air cooled engine.

When in doubt, always follow the mfg's guidelines.

 
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04-30-14, 09:22 PM   #3  
It doesn't run better. Most small engines are only "air cooled". Since high test gas burns at a higher temperature it is recommended that you only use the regular gas in air cooled motors. Your motor will last longer.

Save the high test for liquid cooled motors.

 
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04-30-14, 10:51 PM   #4  
The higher the octane, the slower it burns. That's fine in high compression engines that pre-detonate regular gas and require something slower burning. Not in small engines. In small engines, it reduces efficiency. If it lasts longer in relation to storage time, that's because premium gas often has additives that can help keep it fresher longer.


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05-01-14, 02:42 AM   #5  
Back on the 60's I had a VW. Amoco had what we called "white" gas. Pure and clear, 97 octane. I ran one tank through thinking it would clean the engine out. Within a week both tailpipes literally fell off. It was too hot a gas to use in a utility engine like that.

 
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05-01-14, 04:27 AM   #6  
IMO the best thing is to use ethanol free gas for small engines! Locally we have a website that lists all the stations that sell pure gas, probably the same elsewhere.


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05-01-14, 05:00 PM   #7  
Thanks for the explanation, guys! Regular octane gas it is!

IMO the best thing is to use ethanol free gas for small engines! Locally we have a website that lists all the stations that sell pure gas, probably the same elsewhere.
The nearest gas station with ethanol-free gas that I'm aware of is about a half hour away. The tree farm I do the electric for sometimes gets it in, but I can't rely on it and nor do I want to ask for it all of the time. That stuff runs great.

 
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05-02-14, 03:37 AM   #8  
There are a couple of stores about 20 minutes [opposite directions] from me. While I'll occasionally make a special trip for ethanol free gas, I normally just take the can with me when I'm going that direction for something else. They sell a gas additive designed for ethanol but I don't know much about it and haven't used it.


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