High octane or ethanol free for small en
General Topic
So for outboards, etc is High octane better than ethanol free gas? and the same for 2 stroke?
I use ethanol free gas in all my small engines.
I use ethanol free in all my stuff. Outboard, chainsaws, 4 wheeler, weed wackers, lawn mowers ...ect. I also mix with seafoam every know and then.
Octane level determines how much resistance to compression a fuel has before it detonates. When you add pressure in any system you increase the heat. Higher octane is meant to run in higher compression engines as they are less likely to self detonate and create engine nock as the fuel will try to explode prior to spark.
Octane level naturally deteriorate over time as the fuel ages. So it is a good idea to use high octane on items that may sit weeks/months between use. I use higher octane on my hunting vehicles because they may sit 3-4 weeks with out running. I use higher octane in my fuel tanks that are at my house. If I had a boat that was used only 1-2 month I would go higher octane.
In the 2 stroke engine regular unleaded would be fine as adding the oil changes detonation point, but again if the engine were to sit several weeks a month between uses then higher octane will help prevent issues.
Now ethanol free is a good choice because ethanol in small engines can cause all sorts of issues in the carbs, specifically in carbs with plastic etc.
Also if sitting a long time you can always use stabil fuel stabilizer.
Generally speaking, unless you can adjust/advance the timing, a higher octane just costs you more. If you're like most boaters, run your outboard a few times a month, then non-ethanol is best.........If you're running most days, doesn't matter.....until you store your boat......then run your last tank before storage empty with non-ethanol.
"I use ethanol free gas in all my small engines."
This.....and you'll have no fuel problems with rubber lines and gaskets and rust and all.
^....X3. Ethanol-free (recreational) gas is what I have been going to for many years. BTW.....ya know you've been around a while if you use to put leaded gas in your vehicles.
X4 on ethanol free. Costs more but will save money and aggravation in the long run. My small engine mechanic friend says about 80% of the issues he sees are due to ethanol fuel.
X5. Go with the ethanol free on all small engines, boats and ATV's. High octane is pretty much useless unless you have high compression pistons.
FYI, if you are having problems with older engines vapor locking, your only answer is ethanol free gas. When today's gasoline gets hot, it turns to vapor and doesn't flow properly in carburetor engines, that's why they vapor lock. It works fine in electronic fuel injections because they move the gas under higher pressures. Pressure keeps it in liquid form instead of vaporizing.
You especially need ethanol free gas for any 2 stroke engine. The oil doesn't mix will with ethanol and has ruined many chainsaws and outboards
Ethanol free usually is higher octane. I've found that plastic fuel lines in weedeaters and chainsaws decompose after about five to seven years due to the ethanol in gasoline. My boat motor has never had ethanol gasoline. I learned my lesson with my chainsaw and weedeater.
^.....that too! I put Sea Foam in my atv, outboards, lawnmower and vehicles that will sit for an extended length. The Sea Foam you spray into the plenum of the truck engines seemed to let it run smoother.
For 50:1 mix gas I go 4 gallons Aviation gas plus 1 gallon 85 octane ethanol free gas. Been doing this for years with zero problems. I have been running 85 octane ethanol free gas in the lawn mower, ATV and RZR for years with zero problems.
I use a gas trimmer at the club and have only ever used 40-1 pre-mixed 'Tru Fuel'. 95 octane, zero ethanol. I can fire that thing up with three pulls after it's sat in the shed for 6 months. Not cheap but worth it, imo.
Been using mid octane gas (non-ethanol free) for my two stroke outboard for over 10 years. Same engine, zero fuel related problems. Always add a stabilzer though, Starbrite Star Tron brand.
Ethonal free fuel isn't always readily available...
On a related note, if you live in an area with vehicle emissions required and can't pass due to CO levels, straight E85 will usually get you a pass. Run tank low, put in a couple gallons and then top off with regular gas right after the test. One of the few benefits of Ethanol.
What WYOelker and Joey said. Same BTUs in regular and premium, same "power" in each.... premium just has additives to make it harder to pre- ignite due to high compression.
If your engines don't sit with older fuel you likely won't have any issues. Ethanol gas doesn't like to sit.... eats rubber, turns into gum and goo, stinks like heck, can't hardly wash the smell away. But even non-ethinol will do that given enough time sitting. You just buy more time using it. In the rental fleet we really never had any issues with ethanol gas, but it never sat much and not much that's seasonal. Now that places sell non-ethanol for just a bit more it's what we use. But it's not like it's essential or that we'd pay very much more for it if we had to.
WRT "power", if I recall it has something like 3% more energy per gallon than say, 10% ethanol mix gas? Ethanol has a few less BTUs than gasoline, (76,000 vs 114,000) so the more ethanol the more diluted the gasoline BTU is. 10% mix would hardly be noticeable to most. 15%? Much more than that and many if not most engines require modification.
E85? you do the math.... mine is broken for the day, waiting on parts.....
What does "Stabil" do? Is it necessary in ethanol-free?
100% gas. NO ETHANOL for sure. Like others stated above. I learned this the hard way. Use regular gas in my Mercury out board for years till it quit running. Shop had to replace all the rubber hoses and gaskets that were ate up. That was a $1200.00 lesson.
I've gotten away with 10% eth in lawnmowers for years but snowmobiles, chainsaws, and dirt bikes haven't been tolerant of it. Only use it in a pinch. Otherwise 91 non eth from a local station.
I log with Husky’s. Ethanol free only. I lowered the compression on my 65 Triumph bike so I could run it on the iffy gas I encounter on trips, but always top it and my enduro with ethanol free before winter storage, along with Stabil.
I have been an outboard motor mechanic for 24 years this year. Been around a "few" and have some experience. Higher octane fuel is best for performance and will not stale near as fast. A lot of people steer clear of ethanol based fuel, but I am here to tell you, all fuel does bad things. All the additives that are in gasoline now days are hard of fuel lines, fuel pump diaphragms etc etc I have ran ethanol fuel in my outboards for years with no added adverse effects.
I am not a mechanic. When I can’t start an engine, I have to take it to a shop (minimum of $100!). Since switching to ethanol free, I haven’t needed to take anything (chainsaw, trimmer, log splitter) into a shop. It’s been three years so far.....
Same here. I am 100% ethanol free for everything other than our vehicles. Quads, snowmobiles, saws, and lawnmowers all ethanol free. It’s readily available in northern NY. It’s a game changer IMO. Never have issues starting anything after the winter and I don’t use sta-bil either. Wish I could find it home in Connecticut.
I am not a mechanic. When I can’t start an engine, I have to take it to a shop (minimum of $100!). Since switching to ethanol free, I haven’t needed to take anything (chainsaw, trimmer, log splitter) into a shop. It’s been three years so far.....
If you want your chainsaws and other small engines to run really good try some 100 octane aviation gas. I have a buddy who just sold his small engine shop that he had for decades and avgas is all he ran in the equipment he sold and serviced. Avgas has fewer additives, it smells good when it burns and it doesn't leave an odor if you get it on your hands. I own an airplane so it's easy for me to fill a 5 gallon jug when I'm at the airport. It also makes my 66 Chevelle SS 396 run really good.
Mike...... it's good for your valves, etc. too. If I recall avgas is pretty much the only leaded gas still around.
Marketing is a interesting creature. Gasoline does not come refined naturally "leaded"...it is added precise amounts to boost octane (and helps lube hot things like valves in often real hot high compression air cooled engines). It's great for boosting octane, so good it's still allowed in aviation.
I remember the start of "unleaded" gas and how it was more expensive..... the fuel companies claimed for a time the reason was "they had to take the lead out first...."
Yes TD, avgas is 100LL which stands for 100 octane low lead.
Avgas covers several types of "blends" or "grades". They do make an unleaded version. Back in the day, I had to know them all (and JP) by color as that is how they can be visually distinguished so ya don't inadvertently put the wrong fuel in your aircraft.
Ethanol free is the only way to go
https://trufuel50.com/401-mix/
I buy this in the not-quite-a-gallon size for our brush cutter. Hasn't failed me. Not cheap, but it works great. I get it at Lowe's.
I always used avgas in my 77 Kawasaki Intruder snowmobile. After sitting for almost 10 years I needed to start it to sell it, and it fired up on the third pull. Ran great. I would use it for everything (small engines) but there isn't a source around where I live now.
“all fuel does bad things”
I had always used 10% ethanol gas for everything. I treated everything with Sta-Bill and never had one problem. Once it became available, I started using ethanol-free gas in everything except my vehicles. 87 octane is all we can get here in Cheyenne. Last year one of my generators suddenly wouldn’t start. Took it to the shop and it turned out to be bad gas...two months old. Go figure.
Can you readily purchase Avgas at a small airport, or do you kinda need to “know a guy”?
Unintended consequences: The covid imprisonment put a shut down on ethanol production which led to a shortage of carbon dioxide for breweries. I never use ethanol fuel for anything but I hate to think of buying flat beer.
Question was about outboards.
Answer also depends on the outboard. Merc Optimax for example is designed to run in 87, and you’ll be damaging running premium fuel. High performance engines check what they call for. Everything else run premium.
Can you readily purchase Avgas at a small airport, or do you kinda need to “know a guy”? Likely you can purchase without knowing a guy. They probably won't let you pump it into your vehicle, bring a container.
There are two Optimax. Optimax and Optimax Pro XS.
The Pro XS has been running 88 just fine for me for the past 10 years...
I use ethanol free gas in all my small engines. Never ran better since I made the switch
