Can someone tell me what the correct oil mix ratio is for a 25cc grass strimmer?

Just looked online for manual, but cant seem to find anything….

Cheers, 😉

IIRC, it’s somewhere between 40 and 50:1 for a two stroke (if that’s what you have.)

1:20 or 1:25

Yes it is a 2 stroke engine.

If in doubt go 24:1

If the plug starts oiling up reduce it

50:1 is what we used to use in all our 2 stroke hire tools. One small (100ml) bottle of 2 stroke oil to 5 litres of fuel. Never had any problems.

40:1 in my little McCulloch, (which is what it says on the petrol cap)

You’ve a nice range there. From ‘seized’ to ‘oiled up plug’ 🙂

Surely it depends on the particular make/model?

50:1 in my 21cc Hitachi Trimmer

If you only need to mix small quantities, I’d recommend this:

2-Stroke Oil Mixing Bottle

Fill with fuel to the 1 litre line. Then top up with 2-stroke oil to your chosen ratio.

It should visibly smoke a little.
Lots of smoke = too much oil, no visible smoke = not enough oil.
I’d try 50:1 as a starting point if I’d no way of finding out the correct ratio, but be aware that although too much oil isn’t disastrous, continuous use with not enough is disastrous.

start it with 50:1 drop a bit of fuel directly into the cylinder and rev the bollox out of it come on it a 2 stroke it meant to smoke and seize 😉

Depends on the quality of the oil. A cheap mineral oil might need to be run at 20/25:1, whereas a fully synthetic race 2 stroke oil could be run at 50:1 or leaner. Don’t make the mistake of thinking too much oil can do no harm, IT CAN ! it won’t flow as well through the tiny orifices in the small carbs like on strimmer’s, and can cause a weak mixture and seizing.

My secondhand strimmer has 20:1 molded into the filler cap, I run it on high quality racing 2 stroke @ 50:1 (for over 20 years) and its running as sweet as ever 😉

My hedge trimmer and strimmer only get Castrol R

That smell is the best smell in the world, I grew up with it and I still love it 🙂

I appreciate this thread is about a lawnmower engine but changing the oil ratio solely based on smoke/spooge is wrong in 2-stroke land.

Oil ratio is to manufacturer specs or adjusted slightly due to non-typical use. You change your jetting to control smoke/spooge.

I’d be amazed if its not written on the fuel cap.

Adding too much oil makes the mixture lean (you end up with less petrol in a given volume) and can make it run hot and seize, nothing to do with not flowing though the jets.

oh jota .. ive a gallon of the stuff left over and now you ve made me want to cut the hedge cant wait for monday night

1 Stihl shot bottle in a 5 litre can