Thread: Chainsaw fuel warning

That leaves the question, where did you get your petrol and oil for it?
May help others who buy from the same source

New fuels and oil mixes are creating an ever increasing problem with small motors. I get heaps of chaps with small engines, chainsaws/mowers/brush cutters etc, who have trouble with fuel. Always use fresh fuel and always drain the fuel tank. All this environmental crap is costing us more than it is worth. PAUL.

Always mix your own. I have 4 Stihls from MS 025 to MS 660 using only Stihl 2 stroke oil mixed with fresh petrol. Never had any trouble with fuel over a period of 30 years from owning a mango farm to cutting woodturning slabs. Oh, like they say, you should never loan your wife so never loan your chainsaw.

Yep always fresh and anything older than 4 weeks gets consigned to the mower or whipper snipper. I also generally use one level higher octane than regular petrol. The moment after petrol is made it starts losing octane rating. The longer it sits around in petrol station tanks and then mostly empty containers where it can interact with air the lower it's octane rating becomes.

QUOTE from the still manual

Fuel with a lower octane rating mayincrease engine temperatures. This, inturn, increases the risk of piston seizureand damage to the engine.

Same thing happened to me, except mine was a Sthil. I ended up (after no sympathy from my Stihl agent) complaining bitterly to Stihl who eventually decided to sell me a new one at cost price. I was happy with the outcome. Can I suggest you do the same. It shouldn't happen after 3 hours use. I reckon you should contact Consumer Affairs at least and see what they say.

My Stihl dealer advised me to run double the oil mix for the first few fuel fills, I have done that on all 2 stroke tools, eg chainsaw and brushcutter.

Hi Team, I used up the fuel that came with the saw; walked up the street,to the local (nearest Independent) servo. Filled up 1Ltr in a proper fuel mixing container topped it up with slightly more oil than recommended and stared he machine which ran fine for nearly an hour, stopping and starting several times. No such luck the next day. JayH

Originally Posted by Big Shed

My Stihl dealer advised me to run double the oil mix for the first few fuel fills, I have done that on all 2 stroke tools, eg chainsaw and brushcutter.

Unless a saw is specifically tuned for this increase in oil content in the mix, this is potentially very poor advice.

What happens is increasing the amount of oil in the mix REDUCES the petrol/air ratio, so the saw will run LEAN and is in danger of overheating and seizing the engine.

What the dealer should have said is "leave the oil/petrol as recommended by the manufacturer" and richen up the Mix/Air ratio. Although this reduces overall power it runs the saw a little cooler (a substantial amount of heat is carried away by unburnt fuel) and reduces the chance of cooking the saw. This is what chainsaw millers (should) do routinely to look after their saws to prevent them from overheating during the long hot hard runs involved with chain saw milling.

Modern chainsaw will run from new on 100:1 mix if fully synthetic two stroke oil is used. The reason that manufacturers don't recommend it is because at this ratio mixing up a tankful of mix is difficult to do accurately and getting it slightly wrong can cause big probs.

Originally Posted by jay h

Hi Team, I used up the fuel that came with the saw; walked up the street,to the local (nearest Independent) servo. Filled up 1Ltr in a proper fuel mixing container topped it up with slightly more oil than recommended and stared he machine which ran fine for nearly an hour, stopping and starting several times. No such luck the next day. JayH

What do you mean by SLIGHTLY MORE oil.
A one litre container of petrol needs only 20 mL of two stroke lube to be at 50:1 - the usual manufacturers warranty stated ratio.
If you put in 40 mL of lube that would make it 25:1 - this would make t borderline
If you put in 60 mL that would 17:1 - which would overheat the saw up and permanently damage it.

The average two stroke user thinks that if some oil is good then adding a little (or a lot more) should be better whereas it can be disastrous (see my previous post).
My advice to chainsaw users is to use exactly what the manufacturers manual says and then there can be no argument about it.
There is another good reason to use the recommended amount of lube and that is because it contains a lot more than plain oil. e.g. smoke suppressors which does not combust and hangs around as invisible dust and is not good to breathe in either.

Since your fuel was fresh the excess lube in your mix is a more likely explanation for the fouling of the the plug and serious preignition, leading to the ultimate demise of the saw.

Hi Bob, thanks for your reply, and all the others. In my first post I said the plug was fouled with a mineral deposit not "Oil" that is quoting the Husky man. Slightly more oil was just that about 5% roughly 1 mm on the neck of the container. I could quote far more of what was said by several people who had a lot to say about service stations in general. Apparently this is an increasing occurrence. I won't be buying fuel from this independent again. JayH

It would be interesting to see a picture of the plug.
If you mean a crusty creamy orange or brown deposit that still unlikely to be the petrol and more likely the non-combustible additives like the smoke suppressants in the lube.

Hi Bob, I don't have the plug but It was dark grey with several small, 1/2 mm or less, deposits and one larger 1mm. here was no burnt oil residue on the plug. JayH

I would think that the oil used would be more variable than the petrol. I know that locally (in South Africa) Stihl quote 50:1 for their own oil and 25:1 for other brands, which points to them having very little confidence in other oils.

Originally Posted by Colin62

I would think that the oil used would be more variable than the petrol. I know that locally (in South Africa) Stihl quote 50:1 for their own oil and 25:1 for other brands, which points to them having very little confidence in other oils.

It's the same here but I'm much more conspiratorial than that. I reckon Stihl want's you to buy their oil as you will use less of it.