Fuel for a chainsaw (or any two-stroke for that matter)

27 Apr 2017
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London / Kent
United Kingdom
In another thread I saw
I'd go for a petrol Stihl or Husqvarna - both of which have offers on their hobby saws just now. Use their own fuel and oil meticulously and it will be reliable for many years to come.
and I was curious about this.

I have a Stihl MS171 bought on the recommendation of a friend who has some experience of using chainsaws.

I have had it for just over three years and I have used Stihl two-stroke oil but just bought unleaded petrol from an ordinary petrol station. My friend also recommended a B&S fuel stabiliser which I have used.

I don't use it a huge amount (most of the tree work I do is on the self-sown laurel & holly which are relatively thin and often as quick to cut by hand) but it has had a reasonable amount of use and in autumn 2016 a 30' oak fell down in the garden and I cut that up into manageable sections.

So I was wondering if using Stihl's own fuel (or Aspen fuel which has also been recommended) is better. Or would I not have noticed the difference in three years of relatively light use?
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Just my opinion Stephen but the oil provided by the likes of Stihl and Husqvarna can happily provide lubrication down to a 50:1 mix. I'd still trust a brand such as Oregon but I wouldn't be happy with a general brand that was ok for scooters and such like......chainsaws rev like hell and are pretty stressed motors as they are always flat out under use.
Aspen fuel is great because it lasts in the tank for years and doesn't attack gaskets and seals like ethanol petrol does.
I get many chainsaws and stone cutting saws in with knackered barrels and pistons - usually because the air filters are so blocked, air gets sucked in anyhow and is heavily contaminated.
John :)
In my opinion two strokes don't matter but as with all machinery always strain your fuel and use fuel fit or similar.

The stihl 4mix machines however you should use the good stihl ultra oil as the very low Ash content keeps valves clean etc where poorer oils leaves residues. That's the theory anyway.

If you only do hobby use then aspen makes sense, it doesn't go off is much cleaner and in hobby use the cost isn't such an issue
the oil provided by the likes of Stihl and Husqvarna can happily provide lubrication down to a 50:1 mix
I'm a bit confused. I use Stihl 2-stroke oil, I did say that, it was the fuel that I was commenting on.

My understanding is that the problem with generally available fuel is that it contains ethanol which is hygroscopic and so the fuel gradually takes in water and that it is the water that damages parts of the engine. This is not that much of a problem in cars, etc, where the fuel gets used relatively quickly but for garden tools the fuel may sit in a can for months it can be a serious matter.

Hence the use of B&S fuel stabiliser which, again my understanding, prevents or decreases the absorption of water. Also, I buy fuel for the chainsaw in relatively small amounts, I get c. 2L when I fill up the car.

If, still my understanding, Stihl / Husqvarna / Aspen are basically unleaded fuel without any ethanol in them then I don't see any benefit in using them rather than high street unleaded plus B&S fuel stabiliser.

However I am more than happy to be educated and if a specialised fuel would be better then the extra cost is not an issue.

always strain your fuel

Using anything in particular? Something like a coffee filter (the first thing that comes to mind) has relatively large holes and will let through visible particles.

and use fuel fit or similar.

Yes, Fuel Fit is what I meant by B&S fuel stabiliser.

If you only do hobby use then aspen makes sense, it doesn't go off

I should hope not, the place near me that I buy chainsaw bits at only sells it in 200L drums! They do sell the Stihl fuels in 1/5L containers or it is a c. 30 minute drive to the nearest Aspen stockist.
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Standard car fuel is just fine to use in your saw.....but it does deteriorate if left unused for a long period of time. It also gives the diaphragms / seals a bit of a hard time, hence the use of a fuel stabiliser to help things along. Stihl now own Zama carburettors and are changing the materials that the diaphragms are made from.
For me, I use Stihl fuel when I know the machine will be idle for a long time.....it is either neat fuel or ready mixed for two strokes. It costs around £20 for 5 litres but the a Briggs stuff is fine too.
My own saws maybe use 4 gallons per year, so it's normal petrol plus Oregon oil for me.
Problems I find with broken down machines are people that use old knackered cans to store their fuel - rust particles aplenty! Again, plastic for me. I see no need to strain the fuel if stored in this way.
John :)
My local chainsaw man is 75 and a proper old school type who can identify a saw from the smell.

He has an infamous clear bottle on the counter containing fuel and all the crap he strained from 2 5l Jerry cans. You wouldn't believe the colour, water and sediment in it.

Not all cans are like this but a good fuel strainer will pick up some water particles too. If you think garage pumps are putting out faultless clean fuel every time you are very wrong. I have a fine mesh strainer included in a large funnel that I use after his insistence.
Aspen is cracking stuff, perfect for light use tools. I've got a generator I only use rarely, so I use Aspen in that...got it out to use a couple of months ago for the first time in 18 months and it started first pull
Thanks for the input. All my fuel containers are plastic so no rust particles from them.

Out of curiosity I just ran the fuel I have (maybe 1.5L) through a paper coffee filter. That will be finer than any mesh filter (which all of the external filters I found are) and it picked out half a dozen tiny specks, each much smaller than 1 mm across.

I'm not sure how one could filter water out of fuel, water molecules are quite a bit smaller than, say, octane.
I also find debris in garden machinery tanks is grass or similar which has got in whilst filling. I tip the old fuel out, add a little more fresh stuff and repeat. The filters that sit in the fuel tank are very fine indeed!
John :)

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