Best fuel stabilizer

**David** · 10-25-2025, 08:14 PM

I have been running Mercury stabilizer in my 200XS and BRP stabilizer in our 150HO Etec. The lawnmowers and my Lotus get whichever I have left over. My thinking was that the outboard companies don't make fuel stabilizer but do warranty engines. They should be selling stuff that works.

A few years ago I read an article that said that not all fuel stabilizers work. Today this video came into my in box

https://www.hagerty.com/media/mainte...nge-your-mind/

Some you tuber tested a few different stabilizers. A corrosion with pot metal sitting in E10 with a bit of water added and left for years. And then he checked how flammable the E10 was after a few years

Yup, some stabilizers are still useless. Stabil is best. Yamaha was OK but not great. It was interesting how hard it was to ignite the fuel after years of storage. One can expect hard starting with any fuel stabilizer after storage. For me, this is a question. If the light volatiles are gone, and the fuel is harder to ignite, how would the octane be reduced.

**David - WI** · 10-25-2025, 09:31 PM

It depends a lot on how you use them.
Staybil is just parafin wax that floats to the surface and forms a (less permeable) membrane. You have to mix it up and run the engine to get some in the float bowls, then leave it alone! People who start their stuff once s month or whatever, just burn up the Stabil that was in the bowls andv replace it with straight gas... since the Stabil is all floating on top of the fuel in tank.

**Jim Speros** · 10-25-2025, 09:38 PM

not sure about octane being reduced but I used to go round and round with customers about how old their fuel was. " Oh its not old plus I used stabilizer".
One time in particular owner swore fuel was not that old. It would start and Idle ok but, would not run over 2 grand. Timing would jump around. I swapped ignition parts, sent out his ECU's, pulled my hair out. In the end I ran on my remote tank after draining engine of fuel whalla FIXED.

He eventually confessed he would about once a month kept adding stabilzer.

Another time I pumped white mold from a tank. Customer asked " how did that happen I keep my boat in the garage and I added stabilizer". After doing the math fuel was over 5 years old.

No sense sharing anymore. Seems like 75% of every problem I worked thru was fuel related.

No ethanol in any of my stuff. Boat, lawn equipment not even my ford truck. Thankfully ethanol free is easy to find around me.

**108** · 10-25-2025, 10:13 PM

Marine Sta Bil and Techron.

**4Speed** · 10-26-2025, 08:22 AM

Any thoughts on Startron?

**hellbents-10** · 10-26-2025, 08:25 AM

I don't use stabil, just separates and causes running problems down the road. I like seafoam for my pre winter treatment on the big boats. The old 89 SeaRay 300 has been like that since day one and its fine with the long storage on winter months. My small boats just get rec fuel with octane boost as they can get used at any time.

**Pulse186** · 10-26-2025, 09:14 AM

I use Mercury quickstor. Star Brite Star Tron and Stabil are the only other ones I'll use.

**David** · 10-26-2025, 11:20 AM

Originally Posted by David - WI

It depends a lot on how you use them.
Staybil is just parafin wax that floats to the surface and forms a (less permeable) membrane. You have to mix it up and run the engine to get some in the float bowls, then leave it alone! People who start their stuff once s month or whatever, just burn up the Stabil that was in the bowls andv replace it with straight gas... since the Stabil is all floating on top of the fuel in tank.

As it turns out, one can look up the chemical composition of these products by searching for their safety data sheets. Most hide some information by calling things 'proprietary additives'. None of them use wax. Do the PDF attachments work?

chemical make up.pdf Stabil.pdf

**David** · 10-26-2025, 11:24 AM

It turns out that butane is to blame for the loss of octane

"Butane is a volatile gasoline component used to tailor vapor pressure in accordance with seasonal needs. Cold weather fuel has higher concentrations of butane. Butane has a high blending octane value which helps manufacturers hit their octane targets. The main downfall of butane is that it boils at 32°F. If the fuel tank is vented to atmosphere the butane can start to evaporate out unless the daily temperatures are below freezing. This makes cold weather fuel more susceptible to vapor pressure loss and octane decreases."

Other light organics are to blame for hard starting with stale gas

"A key aspect of gasoline stability is vapor pressure. This is determined by how much pressure builds up inside a sealed fuel container when the fuel is heated to 100°F. A higher vapor pressure suggests a higher concentration of low boiling point hydrocarbons that vaporize under 100°F. Pump fuels with high (12 pounds/square inch, psi) vapor pressures are used in cold weather to prevent engine starting issues due to low temperatures. Pump fuels are limited to 7.8-9psi maximum in warm weather depending on county and state (www.epa.gov). If stored in a vapor tight container the vapor pressure can be maintained for long periods of time. Fuel exposed to the atmosphere can lose light components within a couple of days. Over time as vapor pressure decreases the fuel can become stale. Stale fuel doesn’t evaporate as easily and can cause rough engine idle and hard starting."

https://www.sunocoracefuels.com/tech...w-octane-fuels

Yes I am going down a rabbit hole

**skialot2** · 10-26-2025, 11:27 AM

It's kind of a double edge sword. On one hand they tell you to store a boat with full fuel tanks to help avoid condensation. But then they say not to use old fuel because it does loose octane and goes bad. I use Ethanol Shield or Seafoam during the season but Marine Stabil for longer term storage. After a long storage I like to add a little octane booster just to be safe.

**Jim Speros** · 10-26-2025, 11:37 AM

I have seen damage from ethanol stabilized and not. I am convinced nothing completely prevents damage from ethanol.

Best practice I have experienced is pumping out ethanol laden fuel before lay up.
Best practice in season is to not allow fuel to sit for more than a month.

**Jim Speros** · 10-26-2025, 12:05 PM

When you have no other choice then to burn ethanol I would use Mercury quick care every time I would add fuel. I would add before ramp and aim to burn it all that day.

I had customers swear by Bio bore. I would suggest you use what you believe in and use it religiously every time you add fuel AND fuel for the day and burn it all.

**Pulse186** · 10-26-2025, 12:49 PM

Originally Posted by skialot2

On one hand they tell you to store a boat with full fuel tanks to help avoid condensation.

Don't think it matters either way. You end up with full tank of months old fuel or maybe get a tiny bit of condensation through the season. It is more important the gas is treated regardless of tank volume for winter storage.

I store boats and cars with whatever is left in the tank at the end of the season, make sure the gas was treated long before storage and fill up with fresh fuel in the spring. Been boating a long time and never had a problem.

**David** · 10-26-2025, 01:27 PM

I fill my Allison/200XS tank with ethanol free and add Mercury’s stabilizer. In the past I have avoided WOT until new gas was added. This year I transferred the boat gas to my car, and started the season with fresh ethanol free. I fill the ski boat with the same ethanol free premium with BRP stabilizer and then use it normally. The ski boat motor only requires 87 octane.

The only motor we’ve had a problem with is our 8 HP Yamaha. No start due to bad gas. We took it to the shop thinking something was wrong and the marina mechanic was smart enough to start with gas. That started this for me.

**LakeFever** · 10-26-2025, 01:28 PM

Stabil is best for storage imo but the fuel quality does degrade quickly regardless. Stabil prevents varnish which has killed fuel pumps and carbs and whatnot over the years for me. Sleds mainly. All sorts of these issues back in the day even with leaded fuels. In fact it was worse when I used leaded fuel but that’s probably because I was terrible at all this safe storage stuff. I would run em, park em and that was it until I got round to running again.

My storage these days for my boat is to remove fuel filter, drain, fill with 100% oil and reinstall. Run motor til smoke pouring out. Shut down. Drain the VST. I siphon out all fuel from the tank I can get empty down to a pint or less. I dump a half quart of two cycle oil in the tank along with a little splash of stabil and that’s it. Worked well for last winter