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Unleaded Petrol Problems in Garden Machinery

Shelf Life of Petrol E5 / E10 BP

Unleaded Petrol Problem

You may have heard stories of people having unleaded petrol problems with modern day fuels but may not have experienced, or even be aware of the problems yourself. In the world of Petrol Powered Garden Machinery; we see these problems on a daily basis for 2 main reasons:

  1. Garden Machinery tends to have long lay off periods. Your average petrol mower will stand idle for approx. 4-5 months {during the winter} while the likes of a petrol leaf blower for example, may lay dormant for approx. 8 months {Autumn to Autumn}. During this “down time” unleaded petrol deteriorates rapidly in the fuel system as it is “vented” to the atmosphere rather than being in a sealed container.
  2. Garden Machinery is powered by small petrol engines with carburettors rather than high pressure fuel injection systems found in vehicles. We now have environmental laws governing small engine emissions (Euro V Emission Standards). This means that the vessels within carburettors are becoming narrower to reduce fuel consumption. Unfortunately this is leading to more frequent blockages due to dirt / contaminants within the fuel system.

Is it better to use E5 or E10 petrol?

First of all we need to understand the difference between E5 and E10 petrol. The “E” number is the quantity of Ethanol that has been added to the Petrol you are purchasing: E5 contains 5% but E10 contains a whopping 10%. Ethanol, or Bio-Ethanol as it is often referred to, is distilled from plant matter to make a biologically manufactured, renewable fuel:

This all sounds fantastic on paper but unfortunately there are some negative side effects to this renewable energy. Ethanol is “Hygroscopic” meaning it can absorb moisture from the surrounding environment. This even happens at the filling station, prior to you purchasing the fuel! Their tanks under the forecourt are “vented” to allow the level of fuel to drop as its delivered by the pumps.

But what do the manufacturers recommend?

Manufacturers we deal with such as Briggs & Stratton, Honda, Stiga and Stihl have confirmed their engines are capable of running on fresh E10 fuel. But what is “Fresh”?

Shelf Life of Petrol E5 / E10 BP

This ultimately means that after approximately 30 days, the fuel in your engine has now gone stale and may have potentially attracted water into the fuel system.

Bio-Ethanol is not the only unleaded petrol problem: Over time, the lighter, more volatile elements of unleaded will start to evaporate. The remaining elements have a higher density and will start to form carboxylic acid and a viscous gum that thickens over time. As the fuel ages, the carboxylic acid will slowly attack the soft materials in the fuel system. Rubber, fuel hoses, primer bulbs and diaphragms will lose their flexibility and become brittle. Finally, even the aluminium body of the carburettor will be eroded. During this time, the viscous gum hardens and blocks the internal arteries of your carburettor often causing poor starting / running issues initially. This is not covered by any manufacturers warranty.

Stale Fuel / Water In Carburettor        Stale Fuel / Water In Carburettor

So how do I avoid unleaded petrol problems?

Over the last 5 years or more since E5 was introduced, we have tested various methods to overcome this problem. We have tried many of the leading “Additives” but we have not been convinced by them. We are not particularly fond of combatting additives by adding even more additives! After extensive testing we have found that Stihl’s MotoMix + Moto4Plus have been the best solution to this problem. This “Alkylate” alternative has the benefit of removing nearly all problematic additives while retaining a shelf life of up to 5 years (2 years in a vented fuel tank). You can even extend the warranty of your Stihl product when purchasing Stihl MotoMix 5 Litres under their current promotion.

Alternatively, getting your machinery serviced during its down time in the winter will allow you to run you machine on forecourt fuels all season long.  During a Winter Service we thoroughly clean the entire fuel system and re-fuel with Stihl Moto4Plus to remove any build up of water, stale fuel, dirt or contaminants. This will also extend your manufacturers warranty on new machinery which has a rolling 5 or 7 year warranty period.

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