OutdoorKing Repair Forum Forums Repairs and Maintenance Questions On Hand Held Blowers/Vacuums Petrol Blowers & Vac's 25:1 or 50:1 for my Shindaiwa EB3410 blower?

Hi

I bought a Shindaiwa EB3410 blower (2-stroke) from an authorised dealer in Sydney. The instructions & warranty say that I must use 50:1 so as not to void the warranty, but the 2-stroke mechanic said to use 25:1 as the engine will last a lot longer. He said he can tell the difference between an engine that has run 50:1 as opposed to one that has run 25:1 just by looking at it.

What should I do? Is 25:1 really better for it in the long run as I intend on keeping it for many, many years?

Regards, Paul

Paul, it isn't quite as easy as the mechanic suggested. The amount of oil needed depends on the design of the engine and the quality of the oil. There are three main reasons to try to minimise the amount of oil: reduced air pollution from the burned oil; less carboning-up of the exhaust port, muffler, and piston ring grooves; and extended life of the spark plug. Generally, the major parts of crankcase induction 2 strokes probably will last longer at 25:1. The 50:1 figure is mainly based on the least oil you can use and still get a respectable life from the major parts of the engine - but you will also get less exhaust port and muffler fouling, less tendency to get ring-sticking, longer spark plug life, and if the carburetor has been calibrated for 50:1, slightly more power.

As you can see, this is not simply a matter of "the mechanic is always right" or of "the manufacturer is always right". Leaf blowers usually spend quite a lot of time running at idle or low power, and these are the worst conditions for getting carbon build-up in the engine. If you were a professional forester and this was a chainsaw that you were going to run hard and often, the position would in my opinion be tilted a bit more toward using some extra oil, but for a leaf blower in home use, I end up with the standard recommendation we just about always give at Outdoorking: unless circumstances are exceptional, it's best to follow the manufacturer's recommendation. In this case, that is 50:1.

Hi Paul, and a warm welcome to the forum. Its great to have you aboard.

Generally, we use 25:1 for most 2 stroke applications, and we have had no issues with it...the oil that I use is Shell 2T in the 200ml plastic bottle. I also recommend that you use premium unleaded; as some fuel retailers have a percentage of ethanol in the blend, which should not be used in small engines (It can affect the seals, gaskets etc).
What does concern me is your warranty.....does the 2 stroke mechanic work for the dealer that you bought the blower from?.....If he does, I don't think you will have probs running 25:1, which in effect is just running more oil....which for engine life is a good thing.
Once again Paul, to OutdoorKing.

I find running small trimmers and blowers on 50:1 causes them to overheat rapidly in our summers.

25:1 may choke up the exhaust and spark plug a bit quicker but when I have run them at full thottle all the time I have yet to have an issue with carbon buildup.

Thanks everyone. One more thing is that the mechanic said to use 91RON with 10% ethanol as the 95RON & 98RON have additives in it which are bad for something or other? Perhaps the engine or carby?

I would definately not be putting any ethanol product in my machines, as the ethanol is water soluble and attacks rubber fuel systems.

First, ethanol shortens the life of the elastomers it comes in contact with. That includes a number of fuel system parts, plus the crankcase seals in the case of crankcase induction 2 strokes. Ethanol is also hygroscopic: it absorbs water, which results in the fuel turning yellow and smelling badly. Note that fuel discolouration can also be due to gum formation. The fuel doesn't work very well when it is affected either by water or gum. It is better to avoid fuels that contain either ethanol or methanol (methanol is much more aggressive than ethanol) if possible. Ethanol is used very extensively in the US and Brazil, but is barely used elsewhere in the world (those two countries account for about 80% of global use as a fuel additive).

Second, there are various fuel additives other than ethanol, used around the world as fuel diluents which allegedly improve exhaust emissions, or as octane improvers. The most significant diluents apart from alcohols, are various ethers - especially MTBE, TAME, and ETBE. Metallic substances such as MMT and TEL are sometimes used as octane improvers. All of these additives have disadvantages. The alcohols and ethers are unhelpful to machinery. Some of the metallic additives have adverse air quality effects (notably TEL), and all of them tend to reduce the effectiveness of catalytic converters. Fuels made in some countries, especially the US, often include one or more of these components. None of them except ethanol seems to be used extensively in Australia. Fortunately in Australia it is usual to disclose the presence of ethanol in the fuel, via a sticker on the pump at the petrol station.

Third, high octane fuel can be produced by mixing manufactured high octane oil-based components into the straight-run distilled oil components. Generally these high octane components are produced from crude oil, but whereas the classic way to produce refined oil products was to boil the crude and distill off various lighter components (starting with high octane petrol at the lowest temperature, and working upward through kerosene, lubricating oil, etc), more and more refineries add to their supply of the lighter, higher octane components by breaking down heavier oil components through catalytic cracking and other reforming processes. This is the predominant source of high octane components in Australian fuels. Note that some of the cracked components are prone to forming gum during storage periods, especially if stored at higher temperatures. As a result there is likely to be a greater gum problem with fuels that have their octane improved substantially in this way. Chemical additives can be used to alleviate gum formation, at least to some extent.

Paul, please don't use ethanol in your new blower, whatever the mechanic says, it is NOT recommended by small engine technicians or encouraged by any member of this forum, whose advice you have sought.

Thanks guys. I love these kinds of forums as you get so much knowledge from people who really know their stuff & love to share their knowledge too.