Non ethanol fuel question
- Thread starter Rickcin
- Start date
GearHead36
Well-Known Member
The octane rating for your engine is a minimum. You can go higher with no problem, except for expense. The high octane (especially ethanol-free) will be more expensive.
The reason for my question was because when reading up on using a higher octane in small engines, one article said it can cause small engines to run hotter and possibly cause damage to the valves.
ILENGINE
Lawn Royalty
All of the premium small 2 stroke manufacturers, aka Stihl Husqvarna, Makita/Dolmar require a minimum of 90+ in their products to prevent pre-ignition which will cause engine damage. But premium fuel doesn't burn any hotter than non-premium fuel because it has the same btu rating. The only disadvantage is the higher cost to operate because in most cases will not change your fuel usage.
And my personal opinion is premium stores better, but that may just be my opinion and could be incorrect.
TonyPrin
Well-Known Member
There are several impacts higher than recommended octane can have on a small engine, all negative. Higher octane can make the engine harder to start, run harder and hotter. I'd be careful about using higher octane fuel for long periods (perhaps over 30 minutes) without allowing the engine to cool. The negative impact of higher impact fuels is due to the slower burn rate they produce.
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ILENGINE
Lawn Royalty
And everything you just posted has been proven false. Some of it may of been considered true years ago, but with current fuel formulation is all false. Higher octane reduced pre-ignition but has the same burn rate and btu output as 87 octane.
TonyPrin
Well-Known Member
I try to give my opinion without saying other views are false unless I can prove it. If what I say has been "proven" false as ILENGINE posts, don't just say so. Prove it.
I'm not an expert on gasoline but am fairly knowledgeable. It's well established that octane rating is a measure of gasoline stability; a higher octane is more stable than a lower octane. Octane is determined by the pressure at which the gasoline spontaneously combusts. Engines are designed to operate at a specific compression and octane. When an octane used is different than the octane for which the engine is designed, the gasoline will either ignite earlier, later, or incompletely. Car engines requiring high octane gasoline typically have a compression of 200 psi or more while small engines are closer to 100 psi. Thus, high octane gasoline is likely to combust incompletely in a small engine. Note that virtually all new cars can run on high octane gasoline due to electronic ignition advances.
And burn rate is the speed at which a gasoline mixture burns. That all being the case, how can gasolines that are more or less stable and combust at different pressures have the same burn rate, i.e., rate of speed? And why doesn't incomplete combustion lead to engine issues?
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Skippydiesel
Well-Known Member
Like you Tony I am no expert on fuel standards or performance.
I am with ILENGINI on this matter.
I can not speak for USA fuels however here in Australia we commonly have 91,95 & 98 RON (Research Octane Number). I don't use ethanol blends so won't comment on them.
91 RON is used in small motors and lower performing vehicles. Is the cheapest, non ethanol, fuel
98 RON is used in high performance engines. Is the most expensive petrol
Octane rating is a measure of the anti knock (pre ignition) characteristics of the fuel. The higher the compression ratio of the engine, the more need for anti knock.
Our 98 RON does not store well in a container (fuel tank) that is open to atmosphere, some of its volatile fractions will be lost resulting in difficult starting. There is also a tendency for the old fuel to more readily "gum" up the smaller jets in the fuel metering system.
91 RON seems to stay "good" for very many months without much loss of quality ie from a users standpoint, is more stable retaining its performance characteristics longer than 98.
Using 98 in an engine designed (lower compression) for 91 will result in no benefit OR DAMAGE other than to your pocket.
Using 91 in an engine designed to run on 98 (high compression) will likely lead to loss of power & internal damage to the engine. Symptoms are likely to be a rattling sound (knock) when engine under load and the engine may "run on" after the ignition turned off.
I am with ILENGINI on this matter.
I can not speak for USA fuels however here in Australia we commonly have 91,95 & 98 RON (Research Octane Number). I don't use ethanol blends so won't comment on them.
91 RON is used in small motors and lower performing vehicles. Is the cheapest, non ethanol, fuel
98 RON is used in high performance engines. Is the most expensive petrol
Octane rating is a measure of the anti knock (pre ignition) characteristics of the fuel. The higher the compression ratio of the engine, the more need for anti knock.
Our 98 RON does not store well in a container (fuel tank) that is open to atmosphere, some of its volatile fractions will be lost resulting in difficult starting. There is also a tendency for the old fuel to more readily "gum" up the smaller jets in the fuel metering system.
91 RON seems to stay "good" for very many months without much loss of quality ie from a users standpoint, is more stable retaining its performance characteristics longer than 98.
Using 98 in an engine designed (lower compression) for 91 will result in no benefit OR DAMAGE other than to your pocket.
Using 91 in an engine designed to run on 98 (high compression) will likely lead to loss of power & internal damage to the engine. Symptoms are likely to be a rattling sound (knock) when engine under load and the engine may "run on" after the ignition turned off.
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TonyPrin
Well-Known Member
Skippydiesel, in the interest of space I only quoted a portion of your post. I guess the time difference allowed you to jump in on while we were dosing. I'm sorry you said you didn't agree with me, but your post seems to confirm what I said so I'm hoping you'll switch sides.
The issue is whether high octane fuel can damage a small engine. Per the post, "91 RON is used in small motors and lower performing vehicles" in Australia. In the USA, the octane rating is a combination of RON and MON which calculates to 4-5 points lower than RON alone. Thus, 91 RON is the same as 87 octane. So, when 91 RON is used in small engines in Australia, you're using USA 87 octane, consistent with my earlier post.
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