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My new weed eater uses mid-grade fuel (89 octane). Thats what it was made to use. But my old lawn tractor has only ever had regular (87 octane) fed to it. Would mid-grade make a difference? Would it run better? Would it clean the internal parts of the engine? Or would it burn the engine up or otherwise harm it?

Using a lower octane fuel than specified CAN cause the engine to knock under load,
Note the use of the word CAN
Using a higher octane rating will make no difference except to your wallet but can make life easy and of course the more things that use the came fuel, the fresher it will be .
Ignore 99.999999 % of what your read about fuel grades because it is specific to car - boat -plane engines and not to lazy slow low compression governed mower engines .

I usually follow what the manufacturer recommends. While it is a long discussion I don't want to get into, the molecules in a lower grade gasoline are more prone to self igniting at lower pressures than a premium fuel. Some manufacturers will tell you not to use premium, and others will tell you to only use premium. I find the canned fuel works well in all my engines although it is double or triple gas station fuels cost wise. Here a 5 gallon can is like $100.

Thanks.
What is canned fuels? I have read that canned fuel is the best thing to put through the system for winter storage? Is it different than gasoline?

Ready made Pre-mix for 2 strokes as well.

sofasurfer said:

Thanks.
What is canned fuels? I have read that canned fuel is the best thing to put through the system for winter storage? Is it different than gasoline?

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Yes .
Tip some out in a bowl next to another bowl of regular pump fuel and see the difference in evaporation rates and residue .

Also it will be as fresh as the day it was made and there will be no contaminants in it
It will also be exactly the same day in day out .
And at the price they charge it ought to be .

How long has it been since you've seen a piston damage or meltdown because of spark knock , pre-ignition , pinging or whatever ya wanna call it ?

In a car or motorcycle about 3 weeks in a mower about 5 years

sofasurfer said:

My new weed eater uses mid-grade fuel (89 octane). Thats what it was made to use. But my old lawn tractor has only ever had regular (87 octane) fed to it. Would mid-grade make a difference? Would it run better? Would it clean the internal parts of the engine? Or would it burn the engine up or otherwise harm it?

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No one believes this but I drive thru a local burg which has a no ethanol pump. I take my gas cans with me and fill them there. I run it in 3 lawn tractors dated 1973 through 2009, two newer push mowers, and one 5 year old echo weed eater. I don't have deteriorated rubber gaskets, green buildup in carb bowls, and they start right up in the spring without a fuel system flush. Check it out on Project Farm channel on YouTube. No ethanol gas is about 40 cents higher than E10.

sofasurfer said:

Thanks.
What is canned fuels? I have read that canned fuel is the best thing to put through the system for winter storage? Is it different than gasoline?

Click to expand...

I expect that canned fuel is a no-ethanol fuel mixed as needed to meet the fuel-to-oil volume ratio recommended for the engine. I have used them, they costing about $5.00 per liter. Because of the high cost, I now buy no-ethanol premium fuel and mix high-end 2-cycle oil and the fuel on my own because I use so much of it. With the no-ethanol fue with stabilizer added, I do not drain the fuel systems for winter storage, simply starting the engine, closing the fuel line valve and then running the engine until it stops. I then drain any fuel left in the bowl and the engine fuel system is prepped for storage over the winter. I top off the fuel tank for winter storage with the fuel line valve closed. Using this technique, I have not had any issues with starting following winter storage.

wekjo said:

No one believes this but I drive thru a local burg which has a no ethanol pump. I take my gas cans with me and fill them there. I run it in 3 lawn tractors dated 1973 through 2009, two newer push mowers, and one 5 year old echo weed eater. I don't have deteriorated rubber gaskets, green buildup in carb bowls, and they start right up in the spring without a fuel system flush. Check it out on Project Farm channel on YouTube. No ethanol gas is about 40 cents higher than E10.

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lucky fellow. Here in CA about all we can get that is non-ethanol is either canned mower fuel or canned racing gas these days. All the places listed for non-ethanol are mostly gone now or just sell the canned racing stuff. I used to run AV gas in a boat and race car years ago, but since 9/11 most airports don't want you hanging around the pumps with gas cans.

I live in deep South Ag country, so the 100% gas is around a lot here for farmers etc.. That's all I use..

think I will move to farmer land. How are the twisters this year? Lord I hate those.

The only station near me got rid of the Efree gas and switched to E15. So now i use regular pump gas in everything. I have a 92cc chainsaw with advanced ignition timing and running 200psi compression. It has gone through gallons of regular gas with no issues with preignition. I have never seen a piece of OPE melt down from using regular pump gas.

Higher octane is simply more resistant to detonation, which higher compression engines CAN have. Higher octane burns slower to resist knocking.

Most mower engines are 8:1 or maybe 8.5:1 compression. As in low compression, use any fuel you can buy and dump in. 87 octane is plenty in these engines.

Octane combats knocking. No power increase expected. This comes from the American thinking of more is better, higher octane. Now if you are looking for a power increase use oxygenated racing fuels. $$$$

If all else fails, read your engine manual for proper octane guidance.

sgkent said:

think I will move to farmer land. How are the twisters this year? Lord I hate those.

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I believe anywhere ya live, there will be things to deal with.. Have kin up in PA, they just had another twister scare.

I lived 30 years in S Fla, & the hurricanes just got to be too much..

slomo said:

Higher octane is simply more resistant to detonation, which higher compression engines CAN have. Higher octane burns slower to resist knocking.

Most mower engines are 8:1 or maybe 8.5:1 compression. As in low compression, use any fuel you can buy and dump in. 87 octane is plenty in these engines.

Octane is for knocking. No power increase expected. This comes from the American thinking of more is better.

If all else fails, read your engine manual for proper octane guidance.

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It is because Joe public really do not know the theory
Higher performance engines usually run higher compression, in fact a lot of older engines came with a choice of pistons from 7:1 through to 11:1 which is about the limit of petrol which is why we used to run methanol so we could go from 11:1 to 15:1
Methanol has less energy than petrol but the higher compression ratio liberates more power from the lower grade fuel than you can get from burning petrol.

However people see the more powerful versions of the engine requiring a higher octane so assume all of the power increase comes from the petrol & not from the higher compression ratio
Higher octane petrol usually does have a higher energy density than low octane fuel but not enough to account for the doubling of the HP from an engine that you can get from higher compression ratios.
When I had the time & money to play with things I was working on upping the compression ratio of some side valve engines
The 500cc engine I was playing with had a CR of 4.5 :1
We increased that to 7:1 which is getting near the limit for side valves and the HP went from 11 to 26
Based on he energy content increase of the fuel alone it would have gone from 11 to 11.25
FWIW we were aiming for 40Hp but the crankcase cracked and the con rod bent so it stopped right there
I think the K series HD's nearly doubled the output HP when you made ports in the head thus increasing the CR

Ok. Thanks for all the info.
An engine burning regular will acquire carbon buildup after time. Will higher octane do the same thing? Will higher octane clean any deposits from an engine?

sofasurfer said:

Ok. Thanks for all the info.
An engine burning regular will acquire carbon buildup after time. Will higher octane do the same thing? Will higher octane clean any deposits from an engine?

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The burning of fossil fuels will always result in some carbon residue. That’s just the way it is. If your spark plugs show carbon fouling, your engine could be running too rich. Adjustment of the carburetor can help with that. You can also go to a higher heat range spark plug.

sofasurfer said:

Ok. Thanks for all the info.
An engine burning regular will acquire carbon buildup after time. Will higher octane do the same thing? Will higher octane clean any deposits from an engine?

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Higher octane combats engine knocking. End of message.

If you have a 9.5:1, 11:1 or 12:1 engine, which negates ALL mower engines, THEN you will use higher octane.

Has ZERO to do with cleaning anything, more HP, quicker starts, get the yard cut faster, valve deposits or anything else you might toss in here.

fwiw I began using TruFuel last year. Every piece of equipment I own now starts on the first or second pull - where it used to take 5 to 8 pulls sometimes. This is not an endorsement for the product - just an observation.

slomo said:

Higher octane combats engine knocking. End of message.

If you have a 9.5:1, 11:1 or 12:1 engine, which negates ALL mower engines, THEN you will use higher octane.

Has ZERO to do with cleaning anything, more HP, quicker starts, get the yard cut faster, valve deposits or anything else you might toss in here.

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Add to that because it is more expensive the petrol stations sell less per day so it tends to be staler than e10 or plain unleaded .
Stale is not a problem for a computer controlled fuel injected auto engine but it is a big problem for a carburettor engine

the larger molecules combined with additives take longer to oxidize so they give better protection against pre-ignition, detonation, and pinging. There is no noticeable gain in torque or HP on a governed engine. That said, in our cars, high octane non-ethanol fuels give us about 20% better mpg. The National Academy of Sciences did a peer reviewed study last year which came to the conclusion that when all factors are considered, ethanol in fuels puts out, as I recall, about 25% more CO2 than non-ethanol fuels, and the production of ethanol pollutes the soil, and water substantially compared to non-ethanol fuels. You won't find one Green Advocate in Congress or the Executive Branch talking about the study, even though the definitive science is now proven to be 100% contrary to their positions. The TruFuel we are now using in the lawn equipment is 92 octane non-ethanol fuel.

Yes ethanol in fuels is a con job from start to finish.
Gasahol e-85 to e-95 actually does lower overall pollution in engines designed to run on it.
Alcohol has a much higher detonation pressure so you can run engines on it with compression ratios up to 20:1
You drastically increase the fuel efficiency as you increase the compression ratio so you get higher mpg
It burns cooler so less scrap heat .
Gasahol was used to great effect in South Africa during the BS trade embargos of the 70's & 80's
The down side is that the auto industry did not follow up on this "experiment" and go to alcohol engines big time
IT would be a different world if they had
I used to drive an illegal taxi fitted with a tow motor engine running LPG
It actually had more power , ran better and used far less fuel than identical taxis with petrol engines converted to run LPG and was streets ahead of std petrol engines.
Now the locals car builders moved heaven & earth to get the government to change the ADR for cars to allow them to fit the engines that they already made for tow motors & fork lifts into passenger cars but the government steadfastly reused to do it

I have to somewhat local locations where I can get ethanol free fuel. It is 91 octane. Machines seem to run better, but just a gut feeling