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.

 

Discussion: Getting Rid of 9V Batteries for my Pinpointer (continued)

I wrote a blog post a while back showing my initial attempt to get rid of a 9V battery for my Minelab Pro-Find 35. Since then, I’ve revised my design a few times. The revisions weren’t to improve performance, but instead make it less cumbersome to use.

The purpose of this blog post is to document and share some of these revisions, as well as show you the final iteration. This final iteration still has room for improvement, but for now, I think I’ll settle on its design.

First Revision

I basically just took the wiring and cleaned it up some so it was more compact and contained. I’ll just let me pictures do the talking:

Second Revision/Garrett Carrot

I later was able to pick up a Garrett Carrot as a part of a Equinox 600 package deal I purchased. So I decided to work on this battery conversion so it would work in that pinpointer. I also wanted to do away with the lithium battery. This lithium battery, if not properly maintained (stored with sufficient charge), would literally go bad just sitting in storage.

Perhaps there was some other maintenance I could have done to protect the lithium battery, but I didn’t want a high maintenance battery. So I decided to start using rechargeable NiMH AAA cells. Below are the pictures that show what I did. 

The Third Revision

This worked in both the Garrett Carrot (Pro-Pointer AT) and Minelab Pro-Find 35.

The Fourth Revision

I’ll begin by just showing you the final set up. This is designed for the Garrett Carrot, although it should work in the Pro-Find 35. I can’t confirm the latter as I recently sold that pinpointer because I didn’t need two virtually identically performing (for my purposes) pinpointers.

That last picture is just for kicks. Maybe one day I’ll paint the battery endcap extension green and make the Garrett Carrot look even more like a carrot.

This will run off of alkaline, lithium AAA primaries (with about 1.7 nominal volts), NiCd or NiMH cells. So basically, if you have a AAA cell, it’ll work with this adapter. I primary use it with LSD NiMH cells. This adapter is also reverse compatible in that if I wanted to use the Garrett Carrot with a regular 9V battery, I could. All I would need is a special spacer (wad of paper, piece of foam, etc.) to serve as a filler in the extended battery endcap.

And yes, watertight integrity is maintained even with the battery endcap extension.

Drawbacks

Besides the obvious change in form factor, there are only 2 drawbacks. First, there is the reduced runtime. You can see my prior blog post for a discussion about it, but it’s not a problem as this should easily last an entire day’s worth of hunting (I can recharge at night).

The second drawback is the biggest one (in my opinion). It’s the parasitic electrical draw that the 9V booster chip pulls. Based on my testing, 3 fully charged AAA NiMH cells (about 800 mah of capacity per cell), will be completely dead (as far as the pinpointer is concerned) in about 3 to 4 weeks.

So this is why there’s that red wire and black plug on the side of the adapter. This serves as a switch. I could actually install a switch, but I didn't have a small enough one on hand and I didn’t feel like spending $5 in shipping for a 75 cent (or so) component. But during my next order for electronic components, I'll add a small switch to my order. When the red wire is disconnected, the batteries should last years in storage (they’re Eneloops) and still be ready to go when the time comes. So far, it’s lasted 7+ weeks without any noticeable parasitic power drain.

Now What?

The first major step in removing 9V batteries from my metal detecting gear is done. I’m currently working on using a 4x AA cell rechargeable battery pack to replace the dual 9V battery setup in my Fisher F2.

Discussion: Getting Rid of 9V Batteries for my Pinpointer

LiPo with 9V voltage booster for Minelab Pro-Find 35

I really like batteries, with the exception of the 9V battery. It’s expensive and has poor performance with respect to its internal resistance and capacity. In my opinion, nothing designed after 2010 should be using a 9V battery. Maybe some of you out there can think of a reason as to why a particular device, such as a multimeter or smoke detector should still use a 9V battery, but I doubt that’s possible. And if it is possible, it will be an exception.

I also enjoy metal detecting. However, my metal detector (Fisher Research Labs F2) and pinpointer (Minelab Pro-Find 35) both use 9V batteries. My next metal detector will use AA (Garrett AT series or Fisher F75) or a built in lithium (a la Minelab Equinox), but until then, I’m stuck with 9V batteries…or so I thought.

What’s a Pinpointer?

For you readers out there that aren’t familiar with metal detecting, a pinpointer is a handheld device that helps pinpoint a metal object in a hole or plug you just dug. You don’t have to have it while metal detecting, but it saves a lot of time.

The majority of the pinpointers on the market today use 9V batteries. The three major exceptions are Fisher Research Labs’ F-Pulse, White’s Bullseye TRX and XP’s MI-4 and MI-6.

I set out to create an add-on that would allow my Pro-Find 35 to use something other than a 9V battery. This blog post sets out how I did it.

The Set up

A picture is worth a 1,000 words, so I’ll start with pictures (they're upside down for some reason).

The connectors I’m using are Deans and the blue thing on the right is the voltage booster itself. Here are some of its more notable specs and pics:

Minimum operating voltage: 2.5v

Weight: 0.4g

Maximum quiescent current: 2ma

Minimum input current: 1.4a

Switching frequency: 1.3 khz (PWM control)

Here’s a link to where the item itself, in case you want to order one or learn more about it:

https://www.pololu.com/product/2116

Below are some pictures of it installed in my pinpointer:

Performance

I have not tested this in real world conditions, just indoors using the “hour glass and coin” method. Below you can see how it performs with the stock 9V battery:

I didn’t mark the cardboard, but when using the nickel and the voltage booster, the sensitivity improved by about 1-3 mm, i.e. the hourglass enlarged by about 1-3 mm in all directions except the middle bottleneck.

As for run time, that depends on the battery used. I’m currently using what’s in the pictures and it has 750mah in capacity at 3.7 nominal volts. Fully charged it’s around 4v. Using some rough math, this voltage booster is the rough equivalent of a 9V battery with 330mah of capacity. The typical 9V alkaline battery has about 550mah. Therefore, you can expect about 60% of the run time of whatever you’d get with an alkaline 9V battery. But there are at least two caveats to my numbers.

First, the efficiency of the voltage booster. I don’t know what it is, but I wouldn’t be surprised if it’s around 85%-90%. If I’m wrong, feel free to comment.

Second, the relatively low resistance of my set up. When using the stock 9V battery (it’s heavy duty, not alkaline), the battery has trouble delivering the current necessary when the pinpointer goes off. I know this because the LED slightly blinks rapidly. But this voltage booster set up does not result in the LED light slightly blinking at all.

I think my use of a much higher performing battery than the 9V battery (heck, almost any battery will do better than a 9V) at least partially compensates for the efficiency loss of the voltage booster. I think this compensation effect will still exist when using an alkaline battery instead of a heavy duty, although the effect will be less.

What Are the Advantages and Disadvantages of the 9V Booster?

The sole advantage is that you don’t need to use 9V batteries any more. This can make organizing your battery supply that much easier and save money on an expensive battery type. For some of you metal detectorists out there, this might allow you to completely remove 9V batteries from your metal detecting set up.

Numerous disadvantages include:

- You need a special charger. A typical R/C hobby style charge that can handle LiPo cells should suffice.

- It’s a bit janky, at least compared to a self-contained 9V battery. I intend to clean things up a bit as I tweak this design. I should be able to get most of everything to fit inside a gutted 9V battery.

- At least slightly lower capacity/run time. I don’t know this for sure, but I will assume this is the case for now. Under real world conditions, I wouldn’t be surprised if the run time is about the same with my 1S 750mah LiPo battery.

- If you want to avoid using a special charger and use drop-in AAA cells, you need to permanently modify your pinpointer. In my case, I’d need to cut a large hole in the end cap and effectively lengthen it to accommodate the AAA battery holder like this one:

It won’t be hard to do, but I don’t want to do anything to permanently modify my pinpointer while it’s under warranty.

Bottom Line

For most of you, it won’t be worth using this voltage booster. If you already have a hobby R/C charger and soldering tools and supplies, then you might enjoy this little project and can save some money in the long run by getting rid of 9V batteries

But if you hate 9V batteries as much as I do, you’ll definitely want to consider this.