That time of year - Fuel Additive Time

[joe_db]

It is getting to the time where the next tank of gas is likely to be the last one of the year. I doubt I will be going out much - if any - after Thanksgiving. Every year I put some additive in and some years I use 100 octane no alcohol fuel for the last fill. I have never had anything happen that looked like a bad result with any additive I have used, so I was wondering if there is any science at all behind picking one. So far I have kind of an idea like this:
1. Light oil - Things like MMO. They may be good for the engine, but I do not see how they are a gas preservative.
2. Alcohol - HEET is methanol. This was used back in the no-ethanol days to remove water from fuel. I think it would be counterproductive as an additive now at best.
3. Enzymes - This would be Startron. It supposedly uses "enzymes" to solve storage and ethanol issues. I cannot honestly say if it is marketing BS or what, but I have used it to no ill effect and a lot of people like it.
4. Solvents - This would be Stabil, Valvetect, SeaFoam, and a bunch of others. I think the idea is to counteract the lighter elements of the fuel evaporating and leaving deposits. These too seem to work and have many fans. Valvetect isn't cheap but seems to treat more fuel per ounce of product.

EDIT - from the Startron MSDS:
Solvent naphtha (petroleum), heavy aliphatic 64742-96-7 >75%
It seems at least some of what Starton does is the naptha it is mosly made of.

[Dave Neptune]

Careful

Joe, I have never used a fuel additive in 31 years!! I lay up about 4~5 months in the water and have never had an issue.
Personally I have seen far more trouble with poorly managed (to much and mixed) additives than those running without!
I have noticed no problems yet since the ethanol has been added, however I do use up what I put in except for the layover during the winter (this year with 20 gallons).
I do give my cylinders a spritz of WD-40 while spinning the engine through the plug hole when I do leave it sit for any longer than a couple weeks and that's it.
Just be careful with additives and don't mix them!

Dave Neptune

[BunnyPlanet169]

Is completely empty and dry an option for you?

[Al Schober]

I'm very leery of using MMO as a fuel additive. Rebuilt one engine about 10 years ago with heavy carboning on the intake valves - on removal, the valves looked more like tulips! Don't know the cause for certain, but I suspect long term MMO usage - burning off on contact with the hot valve.
Lead replacement additives - similar story. Another overhaul and the exhaust seats in the block were far gone. Block went to the shop for 'cleanup' and they installed hardened inserts without even asking me - no extra charge.
High octane? You've got to be kidding. High octane fuels are meant for high compression engines to prevent pre-ignition. An Atomic 4 needs high octane fuel like a fish needs a bicycle.

[Mo]

What I do:

Winter / Fuel and Odyssey: When on the hard.

-Stabil
-One small container of gasline antifreeze.
-Fill tank.

This year I'm generally burning about 5 gallons every two weeks. Right now it will take about 10 gallons to fill up. Will top up when the boat is on the hard and prior to that will add the above.

Around here, even in winter, the temp can fluctuate around the freezing mark...+10 C to -20C . These fluctuations can happen with a wind change. January 2009 I think we had +15 C one day and freezing hard the next. This up and down in temps can influence condensation within tanks / partially filled tanks and I prefer to keep mine full. That's my reasoning and it seems to work here for me...otherwise I'd have issues.

I've had only one fuel related issue occur since 2007: I think it happened summer of 2009 (July)...I'd picked up gas at the local gas station, in jerry cans, and poured it in the boat. Not long after that, within an hour, had trouble. Had to pump out the tank, change filters etc....other than that never a problem with fuel.

[joe_db]

I don't care about the octane, but 100LL avgas has no ethanol and it is designed to last longer than car gas sitting in a tank. The pump is 10 minutes from my house, so some winters I make that my last fill and some not.

I'm very leery of using MMO as a fuel additive. Rebuilt one engine about 10 years ago with heavy carboning on the intake valves - on removal, the valves looked more like tulips! Don't know the cause for certain, but I suspect long term MMO usage - burning off on contact with the hot valve.
Lead replacement additives - similar story. Another overhaul and the exhaust seats in the block were far gone. Block went to the shop for 'cleanup' and they installed hardened inserts without even asking me - no extra charge.
High octane? You've got to be kidding. High octane fuels are meant for high compression engines to prevent pre-ignition. An Atomic 4 needs high octane fuel like a fish needs a bicycle.

[Dave Neptune]

Joe, I too used avgas for the winter lay up. I usually would through 5 gallons into what ever was left in the tank. I have not done this as the closed the airport where I had a trailer for a long time on the Colorado River. Have not had access to the avgas for about 10 years now. However I did use nothing but avgas in my hot buggie for the summer layover and the engine was set up to burn the avgas too, except for the altitude part. I don't like to jump it that high.

Dave Neptune

[sastanley]

joe, I am there with you on the av gas. The lead's good for the valves too! (I am just old enough my first car took leaded gas)

I had been considering av gas, but have since found a source of non-ethanol fuel that is reasonable and cheaper than the $6.xx/gal av gas.

A couple years ago, I winterized with the tank as empty as I could get it without physically pulling it. The next summer I had tons of water-in-the-fuel issues. (I ended up pulling it next spring anyway to clean the contaminated tank and get the water out of the fuel)

Last season, I stored it totally full with non-ethanol fuel (a marina in the area sells it for ~$4.15/gal, about a $.40 premium over convenience store gas.) I've been hoarding and collecting jerry cans

I have had zero fuel troubles this year. I've also added 'gas cap o-ring' to the annual maintenance list. I think that was the primary issue with my water problem a couple years ago, but that coupled with an almost empty tank probably allowed for condensation as well.

[marthur]

Here in Michigan we lay up for months (more months than we are in the water lots of years). I usually use nothing except a little two stroke oil (it works like MMO) out of my dinghy can.

I did have some water in the gas this spring, but that was related to a defective o-ring on the fuel filler.

As for lead, I am against it. The valves on the A-4 do not need it and it is a terrible pollutant.

Your mileage may vary (as some are prone to saying) : )

Mike

[joe_db]

Besides for that, it fouls the crap out of low compression engines designed to run on unleaded 80 octane avgas that is no longer made

Here in Michigan we lay up for months (more months than we are in the water lots of years). I usually use nothing except a little two stroke oil (it works like MMO) out of my dinghy can.

I did have some water in the gas this spring, but that was related to a defective o-ring on the fuel filler.

As for lead, I am against it. The valves on the A-4 do not need it and it is a terrible pollutant.

Your mileage may vary (as some are prone to saying) : )

Mike