Two stroke fuel ratio

[pleasant]

29 minutes ago, Johnkv said:

How much oil for a 5 litre can for 45:1?

If using the stihl stuff which is diluted at 100ml per 5l to give you a ratio of 50-1, you will require 105ml of the stuff per 5l can to give you your 45-1

 

Edited March 11, 2023 by pleasant

[Johnkv]

15 minutes ago, Dan Maynard said:

Wrong question really, you should ask whether it matters between 40 and 50. Yes it does. Don't over think it, thousands and thousands of hours of chainsaws have run 50:1 perfectly fine, that's why Stihl recommend it. I'd go with that rather than some bloke on YouTube.

 

(I run 50:1 myself)

 

OK cheers Dan. 

[Johnkv]

3 minutes ago, pleasant said:

If using the stihl stuff which is a dilution ratio of 50-1 at 45-1 you will require 105ml of the stuff per 5l can.

 

Thank you.. 

[Johnkv]

20 minutes ago, Mick Dempsey said:

Why bother asking if you ignore the advice?

Only looking for advice and other opinions  hence the post, thanks Mick.. 

[waterbuoy]

4 minutes ago, pleasant said:

If using the stihl stuff which is a dilution ratio of 50-1 at 45-1 you will require 105ml of the stuff per 5l can.

 

Sorry but, whilst I am not a Stihl agent, I think your maths may be wrong (acceptig that drink has been drunk at this partcular keyboard):

 

Two possible answers to the question, neither of which is 105ml:

 

1  If you are adding the oil to 5 litres of petrol (or 5,000ml) then the amount of oil to get a 45:1 ratio is determined by 5,000/45 = 111mm

2  If you are making up a total of 5l (5,000ml) then the amount of oil needed at 45:1 is determined by 5,000/46 which gives a value of 108ml

 

I've checked these as much as my squiffiness allows:

1  111x45 = 4,995 so as close to 5,000ml as one is realistically going to get

2  (108x45) + 108 = 4,860 + 108 = 4,968

 

As a rule of thumb, if you are wanting 45:1 and have 5l of petrol then I'd be adding 110ml

Thinking about it, this makes sense as you are wanting to alter the fuel:oil ration by 10% and will be adding another 10% of oil

 

Happy to be corrected!

 

(A third scenario might be how much oil to add to an existing 50:1 mix to make it 45:1, but I haven't gone there!)

 

[pleasant]

18 minutes ago, waterbuoy said:

Sorry but, whilst I am not a Stihl agent, I think your maths may be wrong (acceptig that drink has been drunk at this partcular keyboard):

 

Two possible answers to the question, neither of which is 105ml:

 

1  If you are adding the oil to 5 litres of petrol (or 5,000ml) then the amount of oil to get a 45:1 ratio is determined by 5,000/45 = 111mm

2  If you are making up a total of 5l (5,000ml) then the amount of oil needed at 45:1 is determined by 5,000/46 which gives a value of 108ml

 

I've checked these as much as my squiffiness allows:

1  111x45 = 4,995 so as close to 5,000ml as one is realistically going to get

2  (108x45) + 108 = 4,860 + 108 = 4,968

 

As a rule of thumb, if you are wanting 45:1 and have 5l of petrol then I'd be adding 110ml

Thinking about it, this makes sense as you are wanting to alter the fuel:oil ration by 10% and will be adding another 10% of oil

 

Happy to be corrected!

 

(A third scenario might be how much oil to add to an existing 50:1 mix to make it 45:1, but I haven't gone there!)

 

To be fair you are not wrong, but as most peoples measures are in 5ml increments, I thought I would try and keep things relatively simple and easy to remember- even though I disagree with using a dilution ratio of 45:1 for a 50:1 oil

[Johnkv]

On another note, stihl hp ultra is only rated fb that's ISO L EGB. Super is rated fd that's ISO L EGD which is a higher rated oil. Opening another can of worms here but I don't care. I'm convinced ultra is being pushed for environmental reasons, it doesn't even have any info on the bottle! Whereas super has all the info including rating low smoke stabilizer etc.. were being fooled with all this ultra hype I think I could be wrong but I'm open to correction.. 

[waterbuoy]

1 minute ago, pleasant said:

To be fair you are not wrong, but as most peoples measures are in 5ml increments, I thought I would try and keep things relatively simple and easy to remember- even though I disagree with using a dilution ratio of 45:1 for a 50:1 oil

 

That is precisely why I included the penultimate para about a rule of thumb value of 110ml - ie to the nearest 5ml increment

 

 

[pleasant]

some say tomarto, some say tomayto

[waterbuoy]

This isn't a case of english, it is trying to help the OP with his question

 

Is it any wonder that people are using incorrect fuel ratios if the dealerships (which I think you are, but am happy to be corrected) can't get the sums right?

 

I'm not looking to start another forum fall-out on this (far from it in fact given your previous assistance to my question on the use of aspen vs petrol in a new saw), but was merely trying to ensure that the OP has the correct information.  In my experience, if someone understands how a value has been derived then they can work out different alternatives themselves.