Update to thread
As the beginning of this thread says about 3 months ago I posted questions about a display test I saw sitting at a local Harley shop. It showed several brands of fuel additives in small test jars with nail in each. The display was sponsered by K100 and in that particular display it showed all the nails in every test jar had rust formation "except" the K100 jar. The K100 was touted as "preventing" rust.
Well at that time folks on the forum (including myself) were a bit skeptical of the display results. So I figured what the heck, it wouldn't be that hard or take too much time to make my own test of this. So I put 3 different brands of fuel additive, STP, Lucas and K100. A fourth jar I put just plain old gas in it. So I filled them (as described below) and let them sit in my garage for a little longer than 3 months. I wasn't holding my breath for any real confirmation of rust preventitive, but the results turned out rather perplexing so I figured I'd post the update here now.
Original Jars for the test aquired from Baby Food at Walmart, costs 55 cents each and the baby food didn't taste bad. Would probably make a good cheap diet food.
I lost the pic of jars I took when I initially filled them, but they where all the same amout of fuel (3 ozs) and each ratio of additive mix was calculated for 3 ozs of fuel. Had to use a syringe to get the small cc amount. I cut sections of bright finish nails, all were the same kind of non galvanized nail. And they all had a cut end to expose the center metal. And they all had the same surface appearance and no rust on them upon inserting. I dropped one nail section in each test jar.
Once the lids on these jars are opened, they don't seem to seal as tight when reinstalled and I did have some evaporation of on them. But then that was interesting to note also since a gas tank if also vented. And I noticed each mix had a different evaporation rate. Course the seals (once opened) are not scientifically garaunteed the same but still all were fully on and the threads were plastic material.
Pic of all jars at end of 3 months of sitting in my garage, taken on 9-15-2012. Notice some mixes evaporated more than others, they were all the same level of fuel back in June. The tape on them with the dates was the original fill date of 6-10-2012. Also notice that the K100 mix evaporated more than the others. And it became more dark over time. The one on the far left is just plain gas with no additive.
And here are all 4 nails out of the jars and laid on a paper towel.
Here is a close up of the Lucas (on left) and the K100 nails. Notice the K100 has noticeable rust formation on it. These nails were laying on the bottom of the mix completely submerged for 3 months.
And here is a close up of the Plain gas (on left) and the STP nail. The pic turned out lousy but there was "no" noticable rust formation on these two nails. They did darken just a bit, but no actual rust or surface trama.
Basically my results were the only mix that had any rust formation was the K100 mix. Which is kinda strange since they were the ones that said it prevents rust. I'm sure they would say I got my cc mix wrong but I was very meticulus in my doing so. Besides the plain gas mix has "no" rust. So go figure there.
Addionally the Lucas mix (also that brand is called Lucas Oil, but it's a gas additive product), had the least evaporation of all the mixes including the Plain gas mix (which beat the STP and K100 on evaporation). But admittedly the seals were possibly not all the same effectiveness.
Anyhow there you go. Read it if you ain't asleep by now. Moral of the story is just like Smitty said, a full tank of gas is your best rust preventer. However I'm still perplexed as to why the K100 nail rusted when it was submerged the whole time.