2 stroke oil to fuel ratio

[Gerbutt]

I have been wondering about this. I have a combi hedge trimmer, strimmer thing and it says to run 25:1. Whys that and could it be ran at 50:1?

[Stubby]

Yep, all the oil makes it to the combustion chamber, & out through the exhaust, but it does not contribute to the combustion process, so less fuel & more oil in your mix actually results in a fuel deficiency in the air/ fuel ratio.

Now you got my head in a spin, but it is correct.

 

You are dead right . Forget about lubing for a moment . Imagine its a 4 stroke engine . You would put neat petrol in it . You would not " contaminate " the petrol with some oil ? So if the oil can says mix at 50:1 then thats the way to go . No point in putting more than that in .

[chrismechanic]

I have been wondering about this. I have a combi hedge trimmer, strimmer thing and it says to run 25:1. Whys that and could it be ran at 50:1?

 

i would say some engines would need more due to the tolerance in the bore.

or maybe what material the piston and liner are made from.

thats is alot of oil... is it old by any chance?

but i dont know for sure, i am more of a 4 stroke guy.

chris

Edited November 7, 2013 by chrismechanic

[Eddy_t]

Running the saw rich also glazes the bore, lowering compression, and decreasing power, the saw has enough power to pull a 14" pico super chain with the gauges filed down to .75mm through 24+" softwood trees, so all you are doing is lowering the efficiency of the saw, at the same time, you're costing yourself more in fuel and lubricants to get the job done, the 33:1 rating is for cheap oil, whilst the 40:1 is just so it averages out, if you're using the best, run it at the saws best!

 

 

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[GardenKit]

Modern brand name oils such as Stihl, Husqvarna, Aspen, Oregon,Rock etc, which are modern oils designed to run at 50:1.

 

You can run these at 50:1 despite what is said in the book or on the cap.

 

All main brand kit now states 50:1

If buying lesser known brands of oil it may be as well to play safe and run at higher concentrations.

 

If you have smoke then you have too much oil, and as said above the air/fuel ratio will be leaner.

 

It will not cause a lube (or lack of) seize, but COULD contribute to a lean seize.

 

It is bad practice to 'just add that little bit more'

[Eddy_t]

I have been wondering about this. I have a combi hedge trimmer, strimmer thing and it says to run 25:1. Whys that and could it be ran at 50:1?

 

It's either a chinker, or old, either way, stihl oil is 50:1

 

 

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[Gerbutt]

It's either a chinker, or old, either way, stihl oil is 50:1

 

 

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It's a nearly new Sherwood combi. It's cheap but has been fine for what I need. It does smoke like hell on the recommended 25:1, will it be ok on my stihl 50:1 then? Would save messing around with two fuel cans!

[chrismechanic]

well im not sure what brand of oil i have, or the grade/specs as i bought it from homebase and it dont give any info on the container.

all i can tell you about it is, its red and its oil

chris.

[GardenKit]

It's a nearly new Sherwood combi. It's cheap but has been fine for what I need. It does smoke like hell on the recommended 25:1, will it be ok on my stihl 50:1 then? Would save messing around with two fuel cans!

As long as its a reputable oil you should be fine at 50:1

[GardenKit]

well im not sure what brand of oil i have, or the grade/specs as i bought it from homebase and it dont give any info on the container.

all i can tell you about it is, its red and its oil

chris.

I would personally advise against any oil from shed stores, garden centres, garages, supermarkets etc.

 

Stick to main brands from specialist dealers and you know you will be OK.