Review: Ethanol Free Gasoline and Storage Additives Part 2

On May 31, 2018 I placed nine gasoline samples into long-term storage. Part 1 discusses the details in how I went about doing it. But by way of review, I had the following nine samples:

 

- Unopened 50:1 TruFuel

- Unused, but opened 50:1 TruFuel

- “Up to” 10% Ethanol gasoline

- Ethanol free gasoline

- “Up to” 10% ethanol + PRI-G

- Ethanol free + PRI-G

- “Up to” 10% Ethanol + Sta-bil

- Ethanol free + Sta-bil

- Ethanol free + PRI-G with 15 mL additions of PRI-G every 9-12 months or so. I added 15mL of PRI-G on March 12, 2019 and 32 mL May 12, 2020.

 

All of these gasoline samples were purchased on or around May 2018. Of course, that doesn’t mean that’s when the fuel was manufactured, bottled, delivered or refined, but having a consistent purchase date was the best I could do.

 

The purpose of this Part 2 blog post is to explain how these samples performed after 2+ years in storage.

 

How to Test

 

This is where the juice is. Ideally, we could compare these samples to fresh samples on the molecular level, but I have no way of doing that sort of analysis. I don’t have a mass spectrometer and I don’t have the desire to learn how to use one, either. Instead, I’m going to rely on a bit of subjective and objective testing.

 

With respect to subjective testing, I just used my ear to listen to the engine and see how it sounds with a given fuel sample. I also kept note of how many pulls it took to get the engine running. This is a form of subjective testing because I know my arm and shoulder will be unable to use the exact same amount of force to pull on the rope on each pull. I did my best, but take those numbers with a grain of salt.

 

As for objective testing, I used my PET 304 tach to measure RPMs at both idle and full throttle.

 

Testing Setup

 

The engine used would be my Echo PAS-225 with the PAS Power Pruner Attachment. It has less than 10 hours of run time on it before conducting this gasoline test. I then placed this tool on a table and held it in place with my hands. I made sure that I held the Echo PAS in roughly the same manner/position during all relevant times.

 

Except for the TruFuel samples, which already had 2-stroke oil in the fuel, I added the appropriate ratio of 2-stroke oil to the gasoline samples. Specifically, I measured out 400 mL of fuel and mixed in 8 mL of Stihl 2-stroke oil. This 2-stroke oil was brand new, although from a few years ago. I would estimate the 2-stroke oil was from 4-5 years ago. I know this isn’t an ideal situation, but I made sure I used 2-stroke oil from the same bottle in all tested samples.

 

Testing Procedure

 

The test began with the PAS-225 placed on a table and empty of all fuel, although there would be some residue of the old fuel in the carb and fuel tank. In case you’re wondering, until this test, the only fuel the PAS-225 has ever used has been TruFuel.

 

The first sample tested was the unopened can of TruFuel. Taking that sample, I did the following:

 

Step 1: I poured in roughly 1/4 of a tank of the fuel sample and pressed the purge bulb 10 times or so. I did this to flush out any residue of the prior fuel from the carb.

 

Step 2: I poured out the fuel sample from the fuel tank, then tilted the PAS-225 and pressed the purge bulb a few times to remove most of the fuel from the carb.

 

Step 3: I poured out the rest of fuel sample from the gas tank that came from the carb. I then poured in roughly 1/4 of a tank of the same fuel sample then pressed the purge bulb about 10 times.

 

Step 4: I started the PAS-225 normally, ie put it in choke, pulled the cord a few times, put it on run, then pulled the cord until the engine started.

 

Step 5: I let the engine run for about 30 seconds or so at idle, pulling the trigger to full throttle a few times, then shut it off. The purpose of this step is to warm up the engine. All data was to be collected from an engine was already hot.

 

Step 6: Within 10 seconds of completing step 5, I put the PAS-225 on run, then counted how many pulls it took to start the engine.

 

Step 7: I let the engine run at idle for about 45 seconds and recorded the RPMs that the PAS-225 had “settled on,” or otherwise spent the most time hovering around.

 

Step 8: I pulled the trigger to run the engine at full throttle for about 45 seconds and recorded the highest RPM reached.

 

Step 9: I shut off the engine and I emptied the fuel tank of gas. I then tilted the PAS-225 and pressed the purge bulb a few times to remove fuel from the carb. Finally, I emptied the gas tank of this fuel from the carb.

 

Step 10: I repeated Steps 2 through 9 for the remaining eight gasoline samples.

 

I started with the unopened bottle of TruFuel and each succeeding sample was the gasoline that I figured would be the next freshest or otherwise perform the best. For example, I figured the Sta-bil sample would perform the best, the PRI-G the next best and the samples with no additive the worst.

 

A Few Notes About the Samples

 

After creating the samples in May 2018, none of the containers were opened until I created the samples for testing. The only exception was for the PRI-G sample that had extra PRI-G added every 9-12 months. 

 

On March 12, 2019 and May 12, 2020 when I added PRI-G to the appropriate gas can, I shook the can for a few seconds to mix in the sample. I replicated this shaking for all other gas samples, except the TruFuel samples.

 

I mixed in the 2-stroke oil about 4 months before conducting the tests (around the middle of September 2020). This means in addition to the samples sitting in sealed jerry cans for about 2 years, they samples sat in sealed mason jars for 4 months after adding the Stihl 2-stroke oil.

 

Before getting to the results, keep in mind that TruFuel claims its fuel will be fresh for five years if the can remains unopened and two years if opened.

 

PRI-G claims that the fuel can be kept “fresh” indefinitely as long as a sample is added every six to 12 months or so. It also claims it can revitalize aged fuel.

 

The Results

 

Ok, what you’ve all been waiting for, how did these samples perform? Let’s take a look the following chart. Note that the red and blue color has been added merely for ease of reading. I also tested these samples in order, from top to bottom:

 

Sample	Number of Pulls to Start the PAS-225	Idle RPM (“settled on” reading during 45 seconds)	Full Throttle RPM (highest reading during 45 seconds)
Unopened TruFuel 50:1	1	3,290	10,450
Opened TrueFuel 50:1	1	3,290	10,510
Ethanol free gasoline with Sta-bil	1	3,280	10,700
10% ethanol gasoline with Sta-bil	1	3,410	10,800
Ethanol free gasoline with PRI-G plus 15mL added in March 2019 and 32 mL May 2020	1	3,420	10,660
Ethanol free gasoline with PRI-G	1	3,550	10,750
10% ethanol gasoline with PRI-G	1	3,630	10,830
Ethanol free gasoline	1	3,310	10,730
10% ethanol gasoline	1	3,510	10,800

 

Notable Observations During Testing

 

When all the samples started at full throttle, they would start at below 10,000 RPM, often around 9,800 or 9,900 or so. Then they would all gradually rise over the 45 seconds and usually peak after around 35-40 seconds and hover around that level.

 

The first 7 samples did not suffer from any stuttering or bogging down during this slow RPM rise at full throttle. The last 2 (the samples stored with no additives), stuttered/bogged down 2 or 3 times (for half a second or so) during the 45 second time period, but quickly jumped back to “where it left off” with respect to the RPM increase.

 

As for starting performance, they all started on one pull; I couldn’t tell a difference among any of the samples.

 

It also appears that the ethanol gasoline seemed to have higher idle and full throttle RPM readings.

 

In all samples, during idle, the RPMs varied a lot. Most samples had idle readings that varied 200-300 RPM during testing.

 

Conclusions

 

If you’re going to store fuel in a sealed container for 2 years or less, adding a stabilizer/preservative helps, at least with respect to full throttle performance.

 

Sta-bil and PRI-G seem to perform the same.

 

Ethanol, at least at 2.5% to 3.5% levels, seems to improve RPM performance.

 

TruFuel doesn’t have better RPM performance than my stabilized 91 octane gas that the gas stations near me sell. Of course, that doesn’t mean you shouldn’t buy it, as part of what you’re playing for is convenience. Also, most people aren’t lucky enough to have access to ethanol free gasoline, so TruFuel is their only practical alternative. Lastly, my testing methods were crude, so who knows if TruFuel can provide better performance in other ways, such as engine longevity, fuel efficiency or torque.

 

Possible explanations for these conclusions or observations:

 

- The Echo PAS-225 powerhead I was using might be very good at running not-so-good fuel.

- Maybe starting the engine from a “true” cold start would make a difference in performance or ability-to-start.

- The Stihl 2-stroke oil, even though not new, helped revitalize old fuel.

- The PAS-225 runs better the longer it is run. For kicks, after testing all my samples, I retested the unopened TruFuel and got similar idle and full throttle RPM readings. However, they were slightly higher (although still lower than most of the other samples). But would an engine that’s been running for 20 minutes run better than an engine that’s been running for 15 minutes? I would assume an engine that’s fully warmed up would run the same no matter how long it’s been run (as long as it’s not overheating). Perhaps that up to a point, an engine that gets hotter and hotter produces better performance in terms of RPM?

- Maybe the Power Pruner attachment “loosens up” the longer it’s run? Maybe a hotter bar allows the bar oil to be more easily spread due to lower viscosity, and therefore creates less friction which = higher engine RPM?

- Addition of ethanol improves the gasoline’s octane rating, which improves RPM.

 

Keep in mind this is all just speculation on my part. I more than welcome small engine experts to enlighten me.

 

Final Notes

 

I did not gather the temperature, humidity, barometric pressure or dew point weather data for either the duration of storage or the day of testing. However, because all of the storage and testing was done together, I figured the results can be reasonably compared to one another.

 

None of my testing measures or examines the long-term performance of the fuel. I assume that if my PAS-225 started and ran with no signs of trouble or issues, there would be no long-term problems. This is an assumption and I suppose that even if an engine seems to run just fine, there could be some chemical process going on between the additive or aged fuel and the 2-stroke oil. And perhaps there might be premature engine wear? I don’t know and that’s not something I have the time or ability to test.

 

Ideally, I would have purchased in brand new can of 50:1 TruFuel for testing. But I figured the two year sealed can was fine and would serve as an adequate baseline to compare all my other samples to.