Non ethanol fuel question

[ILENGINE]

VP racing small engine fuel is 94 octane

Buy VP 4 Cycle Fuel - Ethanol Free | VP Racing Fuels

VP's ethanol-free 4 cycle fuel is for outdoor power equipment. It protects fuel systems, maximizes performance, extends engine life, & saves you costly repairs.

vpracingfuels.com

Trufuel says theirs is high octane with several references to 92+

Engineered Fuel & Oil | Ready to Use, Pre-Mixed Ethanol-Free Fuel

TruFuel is engineered premixed fuel with synthetic lubricants and stabilizers that are specially made for your 2-cycle & 4-cycle outdoor power equipment.

trufuel50.com

Aspen fuel says theirs is also 92+

Aspen: Fueling the Future

www.aspenfuels.us

So if high octane is bad for small engines then why do all the canned fuel manufacturers have high octane fuel that you claim will burn hotter and damage small engines instead of 87.

 

[Rickcin]

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.

So I guess my original post had some validity but my concern still is as follows;
If the available ethanol free fuel is 91 octane, is it safe to use that or should I mix a little normal fuel (10% ethanol) to dilute the octane rating?

Another point of interest is that since most service stations have 4 different grades of gas with a common hose and nozzle, whenever we make a selection to pump gas, we are going to first receive the fuel that’s in the hose from the last user. The valve to that controls the flow is in the pump, not all the way back to the tank.

I realize it’s only a small amount of fuel, however if you were filling a 1 or 2.5 gallon container, it would be a significant percentage.
One way around this would be to first pump of your fuel of choice into your vehicle so that you get 100 percent of your desired fuel for your mowers or small engines.

 

[Hammermechanicman]

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.

All the saw mfgrs say to use 90+ rated fuel or it will damage the saw. I don't think so. I have serviced over a hundred customer saws run on regular 87 E10 gas. Never seen one damaged from preignition. I have 5 saws that all run on regular E10. Two of them are stihl clones a 361 and a 660. Both of those are ported and run about 190psi compression and advanced timing. After dozens of tanks of fuel usually run with the 25" bar buried in ash haven't seen a preignition issue.

 

[TonyPrin]

So if high octane is bad for small engines then why do all the canned fuel manufacturers have high octane fuel that you claim will burn hotter and damage small engines instead of 87.

For the same reason any business does anything. The fact a business sells something doesn't make it good to use.

I go back to what I said before. High octane gasoline is designed to combust at 50% or more above small engine compression psi. That has to mean high octane fuels will not fully combust in small engines leading to engine issues. Likewise, low octane fuels can lead to detonation (knocking) in high compression engines. Those issues have been resolved in cars due to computerized sensing but still applies to small engines without sophisticated computers.

 

[Hammermechanicman]

The burn rate difference between 87 and 92 is negligible in stock small engines. We are not doing max HP pulls on a dyno.

Has anyone seen a small engine damaged from preignition?

 

[TonyPrin]

Has anyone seen a small engine damaged from preignition?

The issue isn't preignition; it's incomplete or partial combustion. High octane fuels are designed to combust at a much higher compression than small engines produce, on average around double.

 

[ILENGINE]

The issue isn't preignition; it's incomplete or partial combustion. High octane fuels are designed to combust at a much higher compression than small engines produce, on average around double.

I guess it comes down to what you consider high compression 9:1, 10:1 or more.

 

[TonyPrin]

I guess it comes down to what you consider high compression 9:1, 10:1 or more.

Typical BMW compression ratio is 10:1 or higher, while B&S is 6:1.

 

[ILENGINE]

Typical BMW compression ratio is 10:1 or higher, while B&S is 6:1.

The Briggs Vanguard is 8.5:1 Stihl, Husqvarna, Dolmar/Makita all have products in the 10:1+ category. The Kohler Command twin since it has a minimum compression of 160 would be in the 11-12:1 range.

 

[Hammermechanicman]

The issue isn't preignition; it's incomplete or partial combustion. High octane fuels are designed to combust at a much higher compression than small engines produce, on average around double.

High octane fuels are harder to ignite BUT once ignited they burn slightly slower than lower octane rated fuels. In a 4 stroke engine running 3600 RPM the difference is negligible if even measurable. In hopped up 2 stroke chainsaws running 13000+ RPM doing max pulls in wood guys have seen a difference in fuels. A spark plug can ignite 93 just as easy 87 regardless of compression ratio. Putting 93 vs 87 in outdoor power equipment will not cause partial or incomplete combustion.