GAS: Regular? Premium? Ethanol?

[Domush]

I have factory certifications in just about every small engine made. I have yet to attend training where any mention was made as to octane affecting engine, or carb, life. They have, in many sessions, mentioned mid grade will perform slightly better, but have never asserted octane affects longevity. This is from the people who design and manufacture the engines, where they specifically train you to maximize the life of their equipment.

Frankly, I'm inclined to follow the advice of the people who make, and warranty, the stuff. You are welcome to cite urban legend and anecdotal evidence all you like.

The people stating ethanol kills seals are correct for the older stuff, but anything made within the last few years has already been modified to account for ethanol. The manufacturers still don't recommend burning ethanol mix, but it doesn't do the major harm it once did. As for stabil, I've never been told to use it. In fact, I've been warned not to use it by a couple of manufacturers. I've always been told to run the engine with some fresh fuel every month or two, and if that isn't possible, run the carb dry. That said, I do use stabil in my own stuff, but I know it will clog the jets over time. Obviously this isn't an issue for me, as I am trained in just about everything small and performing a carb cleaning is therapy to me.

I would say this is my two cents, but it isn't, it is the research of the people who make the engines you are discussing.

Sent from my SCH-I500 using TractorByNet

 

[cropdusting]

Another premix item.....does changing premix ratio change the air/fuel mixture? Quote from article: A typical example: you go from a 50:1 ratio to a 20:1 ratio. Your engine will now run leaner, and you値l have to make jetting changes. You値l need bigger (in number) jets because the oil molecules are thicker and the flow rate (the amount coming through the jet) is less.

Aha! The volume of fuel has changed. The oil takes up some volume that the gas used to occupy, so your engine is getting less gas and needs to be richened up.


(We used to do quick jetting changes by changing premix ratios when we were ice racing.)

Yes, oil/fuel mix ration affects jetting. On most power equiptment it is not noticable but in high performance applications it is very noticable. Some racers will fine tune with the ratio for changes in humdity and air temp. Typically more bhp can be achieved with more oil (the idea is the more oil the better the ring sealing and higher film strength) this was more back in the days when the only "good" oil was 100% castor oil and engines had no exhaust valves that were prone to gumming/sticking. For this discussion it is highly irrelivant.

Bottom line is I have always followed the manufactures recomendations when operating my engines in "stock" configurations. My modified engines I have to ajdust for the different characteristics of the engine and accept or allow for possibly reduced longevity of certain parts.

 

[ruffdog]

Back in the 80's-90s when I was a mechanic at suzuki, yamaha,and kawasaki dealers, we had many more 2-stroke products than there are now. We would get service bulletins about the technical side of 2-stroke premix and dealing with the new gasohol problems. It is at that point I learned how oil will separate from premix when a small amount of water is added.(ethanol blend fuel) We actually tested this theory in the shop with 10% ethanol and golden spectro oil. I know there was a service bullitin from suzuki(for the RM motocross bikes) that explained loss of octane when oil is added to the fuel. It seems much of this knowledge is not being taught to the young mechanics. It seems they are just taught how to replace parts.

 

[djw250]

I believe that FS130 trimmer is a 4 stroke (4 mix) isn't it? These run pretty high compression and I have always run premium non-ethanol gas and premium synthetic oil in mine (an FS 90). Detonation could be catastrophic in one of these small high performance engines.

 

[cropdusting]

Back in the 80's-90s when I was a mechanic at suzuki, yamaha,and kawasaki dealers, we had many more 2-stroke products than there are now. We would get service bulletins about the technical side of 2-stroke premix and dealing with the new gasohol problems. It is at that point I learned how oil will separate from premix when a small amount of water is added.(ethanol blend fuel) We actually tested this theory in the shop with 10% ethanol and golden spectro oil. I know there was a service bullitin from suzuki(for the RM motocross bikes) that explained loss of octane when oil is added to the fuel. It seems much of this knowledge is not being taught to the young mechanics. It seems they are just taught how to replace parts.

You are correct with this, however modern synthetic or castor blend 2 stroke oils have been developed to nearly eliminate this. Oil separation is almost a thing of the past, but with the "4 stroke revolution" in the motocross going strong for the last 10 years 2 stroke tech is stagnent. Except for OSSA's direct injected 2 stroke.

 

[hizoot]

Yes, oil/fuel mix ration affects jetting. On most power equiptment it is not noticable but in high performance applications it is very noticable. Some racers will fine tune with the ratio for changes in humdity and air temp. Typically more bhp can be achieved with more oil (the idea is the more oil the better the ring sealing and higher film strength) this was more back in the days when the only "good" oil was 100% castor oil and engines had no exhaust valves that were prone to gumming/sticking. For this discussion it is highly irrelivant.

Bottom line is I have always followed the manufactures recomendations when operating my engines in "stock" configurations. My modified engines I have to ajdust for the different characteristics of the engine and accept or allow for possibly reduced longevity of certain parts.

Junk man....I've raced 2 strokes since the 60's and you are right on all you state. The one thing you left out though is when you increase the ratio from say 40:1 to 32:1 you effectively lean out the mixture... as there is less gas and more oil per volume. (less gas is the key)A whole lot of people think its the opposite. It is a good way to fine tune an engine when needed...within reason....,you wouldnt want to richen the mixture by going with too little of oil

BTW : KTM manuals all state that oil mixed with gas will degrade octane by 2 points. One of the reasons to run a higher octane since you dont want to run a 87 degraded to 85.I tightened the squish band on my bikes head,so I have to run a mix of 50:50 race gas (106 octane mixed with 92) as 92 wont keep it from detonating but I dont need the full 106 octane either ($$$$).

 

[Carl Bert]

I have a Mantis 2 cycle tiller and the manual says to use "89 octane". And I have a Stihl string trimmer and the manual says to use "mid-grade with a minimum of 89 octane". And I don't even know of a place in this area where I could get ethanol free gas. So I use the mid-grade gas with Stabil and with Stihl HP Ultra (synthetic) 2 cycle oil. Five years with the Mantis and 7 with the Stihl and no fuel related problem yet.

It's my understanding that when you use a gas oil mix, you don't need to use the Stabil. I always use it in my straight fuel, but never in the mix and I have yet to have a problem, and some of my tools sit for years without being started.

 

[Bird]

It's my understanding that when you use a gas oil mix, you don't need to use the Stabil. I always use it in my straight fuel, but never in the mix and I have yet to have a problem, and some of my tools sit for years without being started.

Carl, you may very well be right. The Stihl HP Ultra 2 cycle oil says on the label that it "contains fuel stabilizer". But the Stabil container says "for ALL 2 & 4 cycle engines" stored or used infrequently. Stabil also says overtreatment cannot do any harm. So I use both Stabil & the 2 cycle oil. Am I wasting the Stabil? I don't know, but for no more than I use, it's not very expensive.

And I guess all the experts and all the manuals say to use "fresh" gas. I've no doubt that's best, but personally I've not seen any harm done by older gas, within reason of course. I always remember the new 2 hp Johnson outboard I bought in 1970. It was a dandy little motor for a canoe and had a one quart fuel tank. But in 1971, I was sent to Northwestern University for the school year. That little motor sat in the garage with a full fuel tank for a year or more. And then it started easily and ran just fine. When it ran out of gas, I dumped in another quart of fresh gas/oil mix, restarted the motor and took off at full throttle and I'll bet that fresh gas gave that little motor another 500 rpm.:laughing: You could sure tell the difference. So the old gas worked with no problem, but the fresh gas worked even better.

 

[joshuabardwell]

It's my understanding that when you use a gas oil mix, you don't need to use the Stabil. I always use it in my straight fuel, but never in the mix and I have yet to have a problem, and some of my tools sit for years without being started.

This has definitively not been my experience. If I left fuel sit for more than about a month, it would just stop running my saw at all, until I started putting Sta-bil in. And yeah, it was mixed with oil the whole time.

 

[Pilot]

]Ethanol is not only a scam but is loaded with problems:

1. It absorbs water.
2. It can corrode fuel system parts that were not designed for ethanol.
3. Crud grows in it.
4. water absorbed in it can freeze and clog your fuel line in cold weather.
5. It develops less power.

A friend couldn't get an engine (I don't remember what kind, maybe a mower) started after letting it sit all winter. Cleaned the fuel system and it was full of crud. See the pic: