2-stroke oil query

[tonyleigh]

I have just bought a petrol strimmer (to keep the weeds trim on the foredeck of course). The manual says not to use outboard oil. Having moved from 2-stroke to 4-stroke for my dinghy outboard I have 3/4 bottle outboard 2-stroke oil I intended to use with the strimmer.

Can anyone explain what the difference is between "agricultural" grade and "outboard" grade and why this warning should be given? Can I vary the mix from the recommended in order to make the outboard oil appropriate for the strimmer?
Many thanks.

 

[steve_cronin]

TC-W & TC

is what it's all about. TC-W is for water cooled 2T's and TC is for engines like motor bikes, strimmers & chainsaws where regular throttle-backs allow oil to re-swamp surfaces.

Your strimmer runs much hotter relying on the rather crude (but effective) flow of air to keep it cool whereas a water cooled outboard or PWC tends to keep at a more regulated (by a thermostat) temperature. Therefore water cooled engines need a thinner oil to do the job particularly in the more advanced "oil injection" engines.

Ash dispersion is also a factor as well as the inability of some T-CW to effectivelly cool piston ring edges.

There is an interesting article at http://www.goa-northcoastoil.com/tips/2cycleol.html by David J. Pardo - Director of Technical Services at GOA Oil Company who explains it more concisely than I could.

Steve Cronin

 

[Trevor_swfyc]

Tony,

Without the oil blend formulae cannot say exactly what the difference is but as said oils are designed for the job they are going to do. Factors such as revs and temperature high revs and temperature may break down components in outboard oil which as said runs at lower temperatures than a strimmer.
The other factor is mix ratio some are 25:1 and some 50:1 also some run in on a stronger oil mix. Buy the petrol in litres it is easier to calculate the oil content a small measuring cylinder is handy to measure the oil 25:1 is 40ml/litre if this helps.
Keep the petrol out of the sun or you will loose the gasses out of it.
I know what sun!
All the best
Trevor

 

[tonyleigh]

Thanks, Trevor & Steve

Many thanks most informative and helpful responses. Steve - first reading of the GOA article is fascinating - have printed off for further study. Ain't Forums great when they come up with such quality answers - thanks.

 

[andyball]

Re: Thanks, Trevor & Steve

The goa article is interesting....but it does suggest (at one point) that pwc's use air cooled 2-strokes,which they don't.....and barely mentions watercooled 2-stroke motorcycle engines, which though rare (for the road) in US, are more popular in the rest of the world and commonly used in MX bikes everywhere, and have oils developed for them....both pre-mix and injector type.

But I would never use agricultural 2-stroke oil in an outboard (except maybe a seagull....even though they're watercooled)