Changing Oil Mix Ratios - Do I Have To Retune?

[Vintage Engine Repairs]

It’s discussed on every forum if it’s necessary to tune if you change your mix ratio. Some firmly believe yes - changing mix ratios (50:1 to 40:1 to 32:2 etc) will require a re-tune - more oil = less fuel. They say you can go as far as to seize the engine, others say they just run really poorly if you don’t.

On the other hand, the other group of people don’t think it will make any difference. It’s a change of 1%-2%. It may change the rpm very slightly, but certainly nothing that will cause the average user of OPE anything to worry about.

I decided to test the theory - “do you have to retune an engine, if the only variable is changing the mix ratio”.

 

[mrxlh]

If you don’t you’re not comparing apples to apples.

 

[Vintage Engine Repairs]

If you don’t you’re not comparing apples to apples.

I don’t understand what you are saying sorry mate. The whole test was to see if the change in ratio requires a change of tune.

 

[stihl livin]

Best to do your own test to find out as there are to many variables.

 

[mrxlh]

I don’t understand what you are saying sorry mate. The whole test was to see if the change in ratio requires a change of tune.

Change from 45:1 to 25:1 or visa versa and tach the saw wot, and at idle, it will tell you you need to retune.

 

[jakethesnake]

Some of my saws need to be tuned at different ratios some don’t. I don’t know the science behind it

Those same ones will need to be returned if I change oil brand. They get on
My nerves a bit

 

[Bryan Newton]

Ok stupid question what about autotune saws do they adjust for the different mixtures

 

[Duce]

Depends on auto-tune version, how many times a second it adjusts.

 

[Bryan Newton]

Depends on auto-tune version, how many times a second it adjusts.

Just curious I have a 562xp autotune but I run 50:1 in

 

[redneckhillbilly]

last weekend I switched my husqvarna saws (572xp and 545) both new this summer from 50:1 to 40:1 using XP+ oil and noticed no difference in how they ran, maybe a tad bit smokier on high idle, but not much at all, both saws reved the sameand had same top end power

 

[Vintage Engine Repairs]

Change from 45:1 to 25:1 or visa versa and tach the saw wot, and at idle, it will tell you you need to retune.

Na you won’t. It may change by a hundred rpm WOT max. From 50:1 to 32:1 the rpm change was 60 RPM.

 

[Duce]

Just curious I have a 562xp autotune but I run 50:1 in

Have owned 3 562's and I run everything at 40:1. Never had a problem. All these oil threads and ratios are just plain crazy to me. Run a Quality 2 stoke oil at 50:1, 40:1, 32:1 and have at it. Running a 550mk2, 572, 592 and ported 372 when cutting firewood without issue, no milling, different story.

 

[Wonkydonkey]

Some of my saws need to be tuned at different ratios some don’t. I don’t know the science behind it

Those same ones will need to be returned if I change oil brand. They get on
My nerves a bit

I’ve noticed that changing oil brands ( probably mineral to semi synthetic and Vice versa) can mean the saw is either fat @wot or won’t tick over, afaik every thing else is the same.

I shall watch that vid now.

 

[bradb123]

Just curious I have a 562xp autotune but I run 50:1 in

I currently have 10 auto tune saws . Anywhere from 550xps up to 592xp . I run Dominator at 36 to 1 and they all run great . The only problem I've had with auto tunes and oil was running a real thick oil such as Klotz r50 and Belray h1r in 10f Temps. The 562s and 572s didn't mind it but the 550s were sluggish .

 

[AlexStromberg]

Have owned 3 562's and I run everything at 40:1. Never had a problem. All these oil threads and ratios are just plain crazy to me. Run a Quality 2 stoke oil at 50:1, 40:1, 32:1 and have at it. Running a 550mk2, 572, 592 and ported 372 when cutting firewood without issue, no milling, different story.

All you have to run is a JASO FD oil. If it says that on the bottle, you can run it. The oil threads sre just for arguing sake.

 

[Wonkydonkey]

I wonder if @Red97 has any info from the dyno with power outputs..

ie is there much of a difference on any non mtronic saws

 

[drf256]

Depends on the oil you pick and temps Tom.

I’ve had issues with Motul800 in small M-tron saws. It’s one of the more viscous oils and it made the mix so thick at 32:1 that the MT couldn’t adjust.

 

[Vintage Engine Repairs]

Depends on the oil you pick and temps Tom.

I’ve had issues with Motul800 in small M-tron saws. It’s one of the more viscous oils and it made the mix so thick at 32:1 that the MT couldn’t adjust.

That’s interesting Al, I I have maxima 927 which is castor based, any idea if that’s thicker than motul800?

 

[kielbasa]

For me, as said before, depends on the temp and oil being used. Redline oil at 32:1 at 10degF ambient, the mix is so thick it has a harder time making its way thru the jets and the saw ran very lean. At those temps I use snowmobile oil and works just fine @32:1. Castor, for me, did the same at 30 degF ambient.
My thought is the retuning has to be done due to the change in viscosity of the fuel mix, not because of simple oil to fuel ratio....

 

[qurotro]

Saber is thicker that Dom.