Posted: 8/15/2011 4:01:42 PM EDT
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1...I just filled my main gas cans for my lawn mowers, weed eaters, chain saws, chipper, tiller and so on with 91 octane since i was too lazy to hang the nozzle up and start over with 87 octane. Will this cause any harm to the small engines?
2...I have several bottles of 10W-30 laying around and would like to change the oil in my mowers and other 4-stroke engines with this. Is this an acceptable weight oil? 
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My stihl and echo stuff recommend 91 octane ETA: I would not use the 10-30 unless that is what it calls for. Air cooled engines often have different oil requirements Briggs factory oil is straight 30weight. Kohler factory oil is 10W-30 Trust me, I work at a lawn mower shop. ETA: Also, this- Quoted:
If you want them to run next year do not put ethanol gas in them. No more than 10% ethanol, meaning no E85 (which is 15%). The ethanol doesn't burn as well as the gasoline- it's really more filler than anything- and it causes the engine to work harder to run at the RPM the governor is set for, thereby wearing out your engine faster. |
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My stihl and echo stuff recommend 91 octane ETA: I would not use the 10-30 unless that is what it calls for. Air cooled engines often have different oil requirements Briggs factory oil is straight 30weight. Kohler factory oil is 10W-30 Trust me, I work at a lawn mower shop. You are correct. We use 40 weight in ours because it's so hot down here. I don't have any kohler so no exp with it |
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My stihl and echo stuff recommend 91 octane ETA: I would not use the 10-30 unless that is what it calls for. Air cooled engines often have different oil requirements Most small engines, especially two stroke do recommend 91 and some won't run on less. I've been using 10-30 for a long time and it works fine. I got tired of buying two different drums of oil, one for pickups and one for mowers. I own a lawn care company and that is my experience so far anyway with 10-30. As the other poster said, don't use ethanol fuels, i've done it a few times in a pinch but some small engines specifically say not to use that type. |
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Actually, the smaller the displacment of the engine (or rather, each cylinder) the less there is requirement for high octane. It has to do with the flamefront traveling across the chamber, detonation ("knocking"), etc. Anyway, small engines run fine on low octane fuel. And if you put in higher octane than an engine requires, it does not hurt, nor does it help. Higher octane helps prevent detonation, but does not burn hotter. It is just more resistant to detonation. Putting 102 octane in your engine will not burn it up, make it run hot, or more powerfully.
Where octane affects power is in a high compression engine. A high compression engine is more prone to detonation, which is harmful. That means instead of burning smoothly from one side of the chamber to the other, the fuel explodes almost all at once. And it does this early, as the piston is still traveling up on the compression stroke instead of burning smoothly on the power stroke. To get a high performance engine to run on low octane gas you have to retard the spark, that is, make the timing lag so ensure the fuel-air mix fires on the downstroke. The engine is not running at max power. So, in a sense, higher octane fuel can give more power, when the ignition is advanced to take advantage of the higher octane fuel's resistance to detonation. And alcohol in the fuel is the debbil. It absorbs moisture from the air, and it dissolves rubber and plastic parts, gums up the works. Run Stabil or Seafoam, or other fuel stabilizer in your small engines, and if possible, no alcohol. |
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If you want them to run next year do not put ethanol gas in them. This is the one big often overlooked problem. And, no ethanol free gas available here now. 
The older small engines have gas lines, internal tank lines, seals, etc. that eventually dissolve in the ethanol. |
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Quoted: Quoted: My stihl and echo stuff recommend 91 octane ETA: I would not use the 10-30 unless that is what it calls for. Air cooled engines often have different oil requirements Briggs factory oil is straight 30weight. Kohler factory oil is 10W-30 Trust me, I work at a lawn mower shop. ETA: Also, this- Quoted: If you want them to run next year do not put ethanol gas in them. No more than 10% ethanol, meaning no E85 (which is 15%). The ethanol doesn't burn as well as the gasoline- it's really more filler than anything- and it causes the engine to work harder to run at the RPM the governor is set for, thereby wearing out your engine faster. E85 is 85% ethanol and 15% gasoline, not the other way around. And it doesn't "make the engine work harder," it makes it run way too lean. |
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91 octane won't hurt anything. I use Star Tron fuel treatment. It is supposed to neutralize the ethanol.
10w-30 is ok. I mix Lucas Oil Stabilizer at 20% into my small engine oil. Don't know if it helps, but I have a 15 year old Craftsman riding mower that uses no oil and has never been apart. |
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E85 is 85% ethanol and 15% gasoline, not the other way around. And it doesn't "make the engine work harder," it makes it run way too lean. your kidding rite? Kidding about what? That E85 is primarily corn alcohol with 15% gasoline, or that E85 makes engines with carbs(and with FI if not properly equipped) run lean? |
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E85 is 85% ethanol and 15% gasoline, not the other way around. And it doesn't "make the engine work harder," it makes it run way too lean. your kidding rite? Kidding about what? That E85 is primarily corn alcohol with 15% gasoline, or that E85 makes engines with carbs(and with FI if not properly equipped) run lean? Yup. The more alcohol you run the more fuel you need. Carb jets tend to run quite a bit larget for 100% alcohol than 100% gasoline. Alcohol also causes corrosion in fuel systems not designed for it. Then there is the fact that alcohol will eat some kinds of rubber in systems not designed for it. |
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My stihl and echo stuff recommend 91 octane ETA: I would not use the 10-30 unless that is what it calls for. Air cooled engines often have different oil requirements Briggs factory oil is straight 30weight. Kohler factory oil is 10W-30 Trust me, I work at a lawn mower shop. You are correct. We use 40 weight in ours because it's so hot down here. I don't have any kohler so no exp with it The secret of facilities maintenance people in Texas for 30 years with small engines was the fleet oil use in those engines –– the manufacturers recommended 30 weight in 103 degree Texas heat because it worked fine in Wisconsin, and if you were smart you used Mystik 15W-50 or Swepco 20W-40 or LE 40 weight or something similar instead. And your small engine would last forever. A very high quality fleet oil would keep them running literally for decades. I know lots of folks who used Mobil1 15W-50 for decades and never replaced a riding mower engine, in Texas, running them straight through the summer, changing every 30 hours or so. OP –– 91 octane is fine, expecially if it has no ethanol in it. |
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So what is the first number and what is the second in 5w-30 or 10w-40? What about straight 30 weight? Where does that fall into the chart? The first number is how the oil behaves when not under pressure (like in a bearing), so a 10W-30 would form a film like a 10-weight oil and under pressure (the second number) the molecules would "bunch up" and form a thicker film, like a 30-weight oil. A straight 30 weight isn't a 10 weight thickened with certain oils that will "bunch up" under pressure –– it's, literally, a straight run oil that makes a 30 weight film. This is really simplified and not completely correct, but close enough. |
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FYI, gasoline runs at about a 12:1 air-fuel ratio, by weight.
Ethanol (ethyl alcohol aka grain alcohol) runs at about 9:1 air-fuel ratio. Methanol (methyl alcohol aka wood alcohol) runs at about 6:1 air-fuel ratio. This is the type used in race cars. There is also the BTU content of the fuel to consider. If you just dump pure Ethanol into a carbureted engine made to use gasoline, it will be very lean. A computerized fuel injected engine can adjust itself, to an extent, but you still have the btu content of the fuel to contend with. Ethanol is just a loser all around. Methanol gives a little more power, but your engine has to suck up twice as much of it, as compared to gasoline, to give that small amount of additional power. Now, what is interesting is Nitromethane... yep, the stuff used in Top Fuel dragsters. This stuff is usually mixed with methanol, but a Top Fuel car can use up to 90% nitro. Nitromethane burns at a 1.5:1 air-fuel ratio. And delivers a lot of btu's per pound. Those engines are supercharged, but the compression ratio is low, 6:1 or so. The interesting thing about nitro is, if the compression ratio is high enough, and cylinder pressure is high enough, it becomes a "monopropellant" and the engine will run on the fuel only, no air needed. It has enough Oxygen in the molecule already... like an explosive. Which it is. And it is corrosive as hell. The alky-nitro residue left in an engine, the alcohol will absorb moisture from the air. The burnt nitro residue combines with that water forming nitric acid. And that really is nasty, corroding parts. Anyway, I know a little bit about fuels and engines. Personally, I don't want any alcohol, methanol or ethanol, in my car, mower, weedwacker, or especially, generator. |
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Now, what is interesting is Nitromethane... yep, the stuff used in Top Fuel dragsters. This stuff is usually mixed with methanol, but a Top Fuel car can use up to 90% nitro. Nitromethane burns at a 1.5:1 air-fuel ratio. And delivers a lot of btu's per pound. Those engines are supercharged, but the compression ratio is low, 6:1 or so. The interesting thing about nitro is, if the compression ratio is high enough, and cylinder pressure is high enough, it becomes a "monopropellant" and the engine will run on the fuel only, no air needed. It has enough Oxygen in the molecule already... like an explosive. Which it is. Back when I was involved in kart racing engines (5hp Briggs flatheads), it was common (although illegal) for people to run nitromethane, propylene oxide, etc. as methanol additives. |