Gas octane rating for mowers?

Not according to the pure gas web site. Regular E0 is available at a number of stations.

Clark… Super… 100 gasoline!

Sponsors of Milwaukee Braves radio broadcasts in the late 1950s, along with Dual Filter Tareytons and someone else. Probably a beer from you-know-where!

I learned it slightly differently.

  • I remember it as octane has negligible effect on flame speed.
  • The higher the octane, the higher a temperature a fuel mixture can reach to before it spontaneously combusts (detonates).
  • Slower flame speed actually increase the tendency to detonate. The reason is a slower flame speed gives the unburned mixture furthest from the spark plug more time to be subjected to the increasing temperatures in the chamber. That increased exposure time raises the temperature of that unburned mixture. If the temperature exceeds the spontaneous combustion temp for the fuel, it detonates.

It’s been a while since I studied this. I am open to any new data.

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Yes, … your owners manual.

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OK. We clearly have an owner’s manual fetish on this board. So 2 things:

  1. As I said, my owners manual says a minimum of 86 octane. Nothing more.
  2. Owners manuals do not always reflect best practice. For example, car tires.
    Nearly all placard recommendations are made a bit too soft, so the ride will feel
    nice. Typically somewhat higher pressure is safer and will extend tire life.

This guy is pretty good and discusses small engine fuels. He’s talking using the store-bought stuff now though. I use too much for the high price of it but interesting.

The manual for my newest Briggs pressure washer just says 87 I think unleaded, but notes that up to 10% ethanol is OK. Really though from the carbs I’ve had apart I don’t see much difference in the internals from new to old. Except the carbs can now be plastic and the floats are plastic instead of brass. The jets and so on are still brass. Main big difference is the new ones have no adjustments to comply with EPA. All you can do is swap jets or drill them out. So far hasn’t been a problem though. Steve above does mention more using the store-bought stuff for storage which might be cost effective but I haven’t had a problem yet. I usually don’t drain the gas though anymore, just run it dry and leave it alone.

Where I live you can buy 10% ethanol gas in all grades from 87 to 93 octane gas , but the ethanol free gas is only available in 91 octane. Most stations don’t carry the ethanol free but Delta Sonic (a car wash chain) and Quik Fill do.

I would be surprised if lawnmower engines are still 6 to 1 compression since they moved to OHV engines,

I bought a Stihl string trimmer for our church a while ago and the manual says that it requires 91 octane.

My Stihl chainsaw just says mid grade 89 octane or better. But then they scare you talking about piston, casting, fuel line, and diaphragm damage. Might be a case to try the Stihl fuel depending on cost. The thing with Stihl though is they only sell through dealers and not on-line. Not much competition here without going to the big city so everything is higher priced. They wanted $8 for a 50 cent screw at Ace with a little grinder work and would have to order it. It’s important to let the engines warm up first before going full tilt with them. Just IMHO anyway.

I have a battery powered trimmer , it is the only way to go.


@VOLVO-V70. I agree with you about the string trimmer. Mrs. Triedaq bought a Ryobi battery string trimmer that I used for at least 12 years. It used a sealed lead acid battery. A couple of years ago I bought a Worx string trimmer at Walmart for less than the cost of a battery for the Ryobi. The Worx is lighter and easier to use than the Ryobi.

I may look at one of those. I’m using an older electric trimmer. It works although the last few summers it keeps getting the string in it messed up for some reason I can’t figure out. But my real challenge is dealing with the heavy duty extension cords getting them unwound, dragged around the yard, and then neatly wound back on the spools. Those extension cords get heavier every time I need to use them.

We’ve gone with 18V Ryobi trimmer, blower, drill, and tire inflator, they work great. I just got an adapter that turns one 18V battery into a backup power source for cell phones and small electrical loads. Would have come in handy last week when we had a power outage.

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Both my daughters love their battery powered trimmers. I have too much trimming to do to consider replacing my gas powered one. The biggest reason for the line to stick on the spool is cheap trimmer line. The cheap line stretches under tension and gets thinner and sinks in between the lines on the spool and when the tension is released it gets locked in place and can’t advance. Get Husqvarna or better line.

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I guess I read an article in Handyman or something about the power supplies and their test of them so it finally pushed me to add them. I bought three of the APS 600A back up power supplies. One for the wifi router etc., and one for each of the main computers. I don’t know how long they would run but I think I could get up to four hours on the wifi and maybe an hour or so on each computer. It would be enough for initial communication and we’d switch to the note book. We don’t have a big problem but did lose power for 4-5 hours a few years ago and it was a hassle. So I figured for the $75 each it would be worth it for the clean power and any minimal power blips. Then I got my generator after that for recharging and refrigerator. You don’t realize how much stuff you have that needs power until its gone.

@Marnet. I bought the Worx trimmer at Walmart and I think I paid about $75. Mrs. Triedaq about 15 years ago bought me a Ryobi battery powered trimmer that replaced the electric trimmer with the cords. Like you, I found unwinding the cords, moving the cord from the electrical outlet in the front of the house to the back of the house a pain. The replacement trimmer is lighter and one charge if the battery will last almost all summer.
My next purchase in outdoor equipment will be a battery powered leaf blower. I am tired of dragging the power cord for my present electric blower around.

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I recommend Ryobi’s 40-volt blower. It is very powerful and runs for quite a while on a charge, yet it doesn’t have the ear-splitting noise of gas-powered blowers. I also have Ryobi’s 40-volt weed-wacker, which–obviously–uses the same batteries. I charge the two batteries alternately, and that way I am always ready to go with either device.

Depends on the station. Around here, you can find premium gas with no ethanol in it. It’s labelled for “off-road use only.” A lot of people put it in their lawn equipment.

I get non-alcohol gas for my boat and lawn tractor at my local Exxon station, but it is regular not premium octane.

I bet your manual doesn’t say to use non-alcohol gas.
Naughty, naughty.