Run Lawn Boy with leaner oil to gas ratio??

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Mar 24, 2005
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Missouri
Mower, 1992 Lawn-Boy S21ZSR
Always used Lawn Boy oil @ 32:1
First, the back story:

The lower seal started leaking again, and oil was sprayed across the deck. 3rd seal in the last 5 years.
1st time I just replaced the seal. 2nd time I checked the crankshaft (even though I never hit anything hard) replaced upper & lower bearings, + the seal. This time, I asked the repair counterman at the lawn, garden & feed supply store what gives?

He asked if the muffler was heavy with carbon. It was. The repair counterman said that the mufflers could get clogged and cause back pressure. Suggest I de-carbonize or replace the muffler & seal.

GET THIS! He also claims that the 32:1 mix is too rich. That Lawn-Boy is an old formulation and that's why they are too conservative on their lubrication standard. He sez that you can run a modern 2-cycle oil in the Lawn-Boys at 40:1 and still provide sufficient lubrication, while keeping the carbon buildup down.

Question:

What say you all? My 2-cycle trimmer, blower, and chain saw all call out 40:1 With the new lubricant 2-cycle formulations - can the ratio be pushed up for this 1992 Lawn Boy as well?

I have Echo Power Blend universal 2-stroke oil
And
Poulan PRO Smokless Forumlation 2-stroke oil
 
My Dad has a Lawn Boy that goes back to the 80s. He runs a 40:1 in it with no problems. . . the plugs actually look better when he replaces them compared to the old 32:1. I think he uses a Shell brand.
 
My main mower is my original 1962 Lawn Boy and I have been running it at 40:1 for the past 15-years, and I do not use Lawn Boy oil.

The mower I use for bagging is a later model Lawn Boy (made by Toro) with the Toro 2-cycle engine (muffler on engine on top) and I also run the 40:1 in it also even though they recommended the 32:1 mix.
 
Id run amsoil saber or mobil mx2t... make sure the right formulation is selected and go for it!
 
Citgo Sea and Snow very good clean burn and cheap at 40:1 been using for years in my lawn boy.
 
32:1 is definitely old school. Many of the older 2 cycle engines ran on that stuff for years, but suffered carbon issues by doing so. The old school of thought was that they wanted to make sure it wasn't run too lean, so they erred on the rich side as a precaution. [censored], they even had 16:1 for years before that! I've seen many entire muffler ports plugged solid with carbon because of rich mixtures.

You can definitely run any of the modern oils in your Lawnboy without doing it any harm. The very biggest misconception about 2 cycle oils is that people think a certain engine MUST run a certain ratio. Not true. The ratio is determined by the oil, not the engine. Any modern oil mixed at the ratio it was designed for will work well. Stay away from any oil that has a ratio chart on the back of it. There is only one optimal ratio for any given oil, period, and any oil with a chart on the bottle is misleading about that fact.
 
I've been running 40:1 for years too.
The local Lawn-Boy mechanic told me it was OK to do, (only exception is the older self propelled models-they use the oil for lubing the drive unit).
I'd use a good quality brand of 2 cycle oil.
Some have air cooled and water cooled versions.
Use the air cooled. There is a difference.
Snowmobile oil, for air cooled engines works well too.
 
Well, two things.
1. I have never seen a 2T lawn mower... Maybe a US thing.
2. I have seen ONE engine requiring more oil than 1:50 and that was my old 4hp johnson outboard asking for 4% or 1:25. Otherwise it is 1:50.

In any case make sure you use the right oil for the engine temp, air cooled och water cooled, high rpm or low rpm.
 
I tried 50:1 Stihl ultra, and got a knocking and surging after 15 minutes of operation. My first fear was to blame the oil. Well the intermittant surging continues even with a switch back to 32:1 dino. Cleaned the carb, pulled the jets, new air vane, and govenor spring, and it still surges. Known problem in the durafoce, but it took 9 years to start. I have an air leak, loss of compression or I need to drill out the jets. I will dig out my compression tester tonight.

I have never had carbon build up in 9 years running 32:1 Valvoline multipurpose dino 2 cycle. I run seafoam in the gas I mix the oil with.

I may try the 50:1 again. While it is a leaner/lighter oil ratio, it is a richer fuel mix (More gas to ignite) and might even out the RPMS. I will try it before drilling out the jets.

For any lawnboy nuts try this site. They are serious collectors and pretty knowledgable.
http://www.mytractorforum.com/forumdisplay.php?f=155
 
Originally Posted By: dwendt44
I've been running 40:1 for years too.
The local Lawn-Boy mechanic told me it was OK to do, (only exception is the older self propelled models-they use the oil for lubing the drive unit).
I'd use a good quality brand of 2 cycle oil.
Some have air cooled and water cooled versions.
Use the air cooled. There is a difference.
Snowmobile oil, for air cooled engines works well too.


Lawn bow recommends TCW3 for watercooled engines, as the lawnboy operates at lower RPMS and Temps than other air cooled power equipment. (2004).The new MTD snow blower (2008) recommends 50:1 synthetic Jaso with basically the same lawnboy Duraforce engine.

Maybe they have come to agree with you the oil got better.....or
the EPA got tougher.
 
Last edited:
I have always ran 32:1 or 40:1 depending on the usage. I bought a new Echo chainsaw and they recomend 50:1 with their Echo oil.

Took me a while to actully get it through my head that it would be ok but so far been ok.
 
Originally Posted By: Pablo
I would use Amsoil Saber at 50:1


+1 in a LawnBoy

Sabre' is all I use at 50:1 in my CCR 3000 Toro/Suzuki Snow blower and Echo blower and trimmer.

It's a no brainer.
 
Saber 80:1 won't hurt your LawnBoy. That stuff definitely can take some serious abuse. We ran it in a post hole digger for weeks last year at 100:1 in nasty impacted clay and life was still good! The manufacturer's recommendation was 32:1 for this highly stressed beast. I really enjoy the one squeeze packet to a single gallon can of gasoline simplicity...even illiterate "guest" workers can't screw that up. Engines just don't bog down as much when you run them at the leaner mix ratios with Sabre pro.
 
Originally Posted By: Cmarti
I tried 50:1 Stihl ultra, and got a knocking and surging after 15 minutes of operation. My first fear was to blame the oil. Well the intermittant surging continues even with a switch back to 32:1 dino. Cleaned the carb, pulled the jets, new air vane, and govenor spring, and it still surges. Known problem in the durafoce, but it took 9 years to start. I have an air leak, loss of compression or I need to drill out the jets. I will dig out my compression tester tonight.

I have never had carbon build up in 9 years running 32:1 Valvoline multipurpose dino 2 cycle. I run seafoam in the gas I mix the oil with.

I may try the 50:1 again. While it is a leaner/lighter oil ratio, it is a richer fuel mix (More gas to ignite) and might even out the RPMS. I will try it before drilling out the jets.

For any lawnboy nuts try this site. They are serious collectors and pretty knowledgable.
http://www.mytractorforum.com/forumdisplay.php?f=155


I use the Stihl Ultra in all my trimmers and blowers. I was thinking of running this same mix in my M series Lawn-Boy that specifies a 64:1 ratio to avoid two mixes and keep a fresh mix for the Lawn-Boy. Is the Stihl Ultra mixed at 50:1 OK for the Lawn-Boy?
 
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