Sta-bil, PRI-G or Additive Free: Does it Matter?

mh9162013

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After more than two years, I finally finished my gasoline sample testing, where I compared various fuel samples in terms of their performance and ability to start in a 2-stroke engine.

My results:



SampleNumber of Pulls to Start the PAS-225Idle RPM (“settled on” reading during 45 seconds)Full Throttle RPM (highest reading during 45 seconds)
Unopened TruFuel 50:113,29010,450
Opened TrueFuel 50:113,29010,510
Ethanol free gasoline with Sta-bil13,28010,700
10% ethanol gasoline with Sta-bil13,41010,800
Ethanol free gasoline with PRI-G plus 15mL added in March 2019 and 32 mL May 202013,42010,660
Ethanol free gasoline with PRI-G13,55010,750
10% ethanol gasoline with PRI-G13,63010,830
Ethanol free gasoline13,31010,730
10% ethanol gasoline13,51010,800

To get a better idea of what these results mean and their context, you can read my blog post: https://gadgetsoftheoutdoors.blogspot.com/2020/09/review-ethanol-free-gasoline-and.html

TL;DR: if you're gonna store your gasoline in a sealed container for less than 2 years, Sta-bil and PRI-G seem to perform the same. And if you don't use any additive, don't worry, your fuel is still very usable, although you'll notice some slight under-performance at full throttle.
 

bertsmobile1

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Nice piece of work and thank you for sharing.
Down side it is meaningless for any one else but you and the fuel you were using.
There are so many factors that affect fuel quality that blanket testing like you have done is irrelevant .
Factors include the age of the fuel you used before you got your hands on it
The day & night temperatures where the testing was done
The dew point
The relative humidity
The altitude
The actual air quality

This is why testing is always done under standardized conditions in labs so the comparisons are just the fuel addative.
I for one never bother as most are little more than surficants but some swear by them
 

mh9162013

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All those variables you mentioned were the same, during both testing and storage.

In that chart, there were 9 total samples tested, but they all came from 4 sources (2 cans of TruFuel, a few gallons of ethanol free gas and a few gallons of "up to 10%" ethanol gas, which had 2.5%-3.5% ethanol). All samples were created and stored within a 2 hour window, all samples were tested within a 1.5 hour window, all samples were stored in the same location and under the same environmental conditions. Except for the TruFuel, they were all stored in the same brand and model of gas cans.

Excluding the TruFuel, the only variables were the ethanol content of the gas, the existence of additive and the type of additive.

If you read the two blog posts (Parts 1 and 2), you'll see that everything has been standardized (for the most part).
 
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bertsmobile1

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The point is if I did the exact same testing here there is a better than average chance that my results would be different to yours
The same tests done in Texas would give different results to being done in Alaska .
I am at one with you, most of the goos are the proverbial snake oil .
But the reality of things is people use them under anything but a standard condition and expect them to work regardless of weather they have a full tank of fuel or a 3/4 empty tank of fuel, weather the fuel is in a steel stand alone shed or a brick garage adjoining the house , etc etc etc.
And all of these have a drastic effect on the outcomes.

As mentioned before, I store a motorcycle 450 yards away from my landlords house.
We can both return from a ride in summer, fill our tanks from the same nozel at the petrol station then ride home.
In 2 weeks , my bike will start right up while his won't and will regularly foul a plug.
I can store fuel in drums for months , which I regularly do because of wild price flucuations and have no problems when using it.
Nothing in his shed will be good after a month .
Like crash testing cars or oil testing , fuel testing is not designed to test it's response to actual use .
It is designed to test the effects of making changes to the product , not how well the product works.
 

mh9162013

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I would agree your results would be different than mine. But I would predict that the effect of the additive for you would be comparable to the effect it had for me, as long as you were using the same tach, Echo PAS-225 powerhead and Power Pruner that I used.

I know my experiment leaves a lot to be desired. But it's not due to lack of variable control. Rather, it's due to inadequate testing methods. For example, I'd love to have tested fuel efficiency, engine wear and torque.
 

bertsmobile1

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Absolutely nothing wrong with your testing, in fact I would give you a very well done for it.
Problem comes when people extrapolate the results to their own enviroment .

We have compulsory seat belt wearing down here .
I ran a small local delivery company using vans so the last thing I wanted was to be crushed between a seat belt and whatever had slid forward from the back.
Then there restrictions when making sudden moves to check the side windows plus getting in & out better than 100 times a day.
I got off a not wearing fine after constable keen started to lecture me about crash test dummy results.
After me breading him for 20 minutes solid about extending the results from totally artificial testing to real lfe situations he finally got embarassed when his supervising sergent had to agree with what I was saying .
The lack of proper education of local police is very dissapointing .
Reminds me of another case when another new officer was about t fine a taxi driver for leaving his cab to fill with LPG while he took a piss .
She honestly believed that the big tank of LPG connected to he cab would cause the small tank in the cab to explode & start a major fire .
 
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