Fuels ain’t fuels

This article is reproduced from the April 2019 edition of our Cruising Helmsman Magazine.

Andrew Norton details the effects ethanol added fuels have on outboard engines and fuel tanks and the result is not good. Norton includes testing procedures and steps you can take to overcome the problem.

TOUTED by successive federal governments in Oz, since the mid-nineties, as environmentally friendly and non-damaging to engines, E10 is anything but that. E10, or standard 91 RON (research octane number) unleaded, blended with ten per cent ethanol, has drawbacks that make it particularly unsuitable in a marine environment.
The main one is known as phase separation, which occurs because, like diesel, ethanol is a hygroscopic fuel or one that attracts moisture. In fact, petrol needs to have only 0.5% water content or five millilitres per litre in it before the ethanol will absorb this water and separate from the petrol. The ethanol/ water mix sinks to the bottom of the fuel tank, right where the fuel line pick-up is located. The carburettor will then draw in this mix and obviously the engine will stall, necessitating draining the carbie bowl and cleaning out the high and low speed jets. Of course the fuel tank will need to be drained too.
If your tender is large enough to be powered by fuel injected outboards such as the Suzuki DF15/20 and Tohatsu MFS 20E, the ethanol/water mixture will seriously damage injectors because, unlike petrol, water does not compress easily. The entire fuel injection system will need to be stripped, cleaned and re-assembled, a complex task. Phase separation can occur in as little as two weeks from when the fuel was blended at the refinery, particularly in humid tropical climates, so if an engine is used infrequently this will be a constant issue.

Another drawback is that ethanol is an oxygenated fuel. The normal main jet air/ fuel ratio is 14.7:1. Using E10 will lean out this ratio to 16.2:1. Not only will power be down because the engine is running too lean but also the leaner mix burns hotter, which can damage the exhaust valve(s) in four stroke engines.
Ethanol has only 65% the calorific value per litre of standard 91 RON petrol, which translates to less combustive energy. E10 has 6.5% less energy than non-ethanol unleaded which means the engine uses more fuel and this negates any cost savings made at the fuel bowser.
Last but not least are the solvent qualities of ethanol, which can dissolve fuel lines and carbie gaskets in older outboards that were never designed to be used with ethanol fuels. This means outboards made prior to the mid-nineties.
I have experienced this first hand with older engines where the fuel lines literally dissolved into a gooey mess, necessitating fitting new lines and never again using fuel in these engines unless tested first.
Older outboards such as British Seagull and Archimedes (Volvo) Penta two strokes and Ocean four strokes should never be run on E10, nor should Blaxland Chapman two stroke and Simplex and Olds four stroke inboard engines.
If you have an older fibreglass yacht with an inboard petrol auxiliary, using E10 in built-in fibreglass tanks will actually dissolve the resin in the fibreglass into the fuel and this will bypass the filters and clog the carbie and coat the valves and cylinder walls, necessitating expensive repairs. Dissolving fibreglass tanks in the US has been a real issue ever since ethanol blended fuels were first marketed.

Major fuel companies such as Caltex are reputable when it comes to 91 RON unleaded not being blended with ethanol, though it still pays to check the labelling on the fuel bowser.
One major oil company that used to sell non-ethanol 91 RON now states: “may contain up to ten percent ethanol” next to the fuel bowser so I have axed buying fuel of that brand. I found this out the hard way when long-term testing a four stroke Mercury F2.5 outboard in 2015.
Previous batches of this brand of fuel were fine but the Merc kept ‘hunting’ at low rpm and stalling when idling, indicating phase separation in the fuel tank was well under way.
Some independent outlets I have tested add up to 4% ethanol in fuel sold as nonethanol 91 RON. Examining the colour of fuel does not indicate the presence of ethanol so the fuel needs to be tested or use premium 95 RON, which normally is free from ethanol.
However, while tests I have conducted show that most 95 RON premium does not contain ethanol, some of the fuel tested has been tainted, so paying more for fuel doesn’t always mean it is better quality. Note that while 95 RON can be used in all two stroke engines, inboard and outboard, providing a semisynthetic oil is used, it cannot be run in all four stroke engines. More on this in part two of my fuel series.

The only way to be certain fuel bought does not contain ethanol is to use a specific test kit. The best I have used so far is made by US fuel test specialist MLR Solutions.
Ethanol-tainted fuels are a real problem in the US where E15 is common, regular (87 Anti Knock Index or 91- 92 RON) unleaded blended with 15% ethanol. Most engine manufacturers state up to 10% ethanol content is allowable under new engine warranties, but using E15 voids these. So every batch of fuel bought needs to be tested.
The fuel testing kit comprises a plastic bottle with a screw-on cap and squirt nozzle. The cap opening is large enough to allow a fuel bowser nozzle to be inserted in it, although the bottle holds only about 200ml.
The next component is a glass tube with rubber stopper and graduations moulded into the glass from zero to 30% ethanol content. Finally there is MLR’s own blue ‘Quik-Check’ dye to help show the ethanol percentage more clearly.
Using the kit is simple. Water is added to the ‘water’ marking on the glass tube, then petrol added from the plastic bottle to the tube, up to the level marked ‘gas’. One drop of Quik-Check is added to the tube and the rubber stopper fitted.
The tube needs to be shaken vigorously for 30 seconds then held upright to allow the mixed water and petrol to settle, which can take from three to ten minutes to get an accurate reading. Any ethanol content will be clearly indicated on the ethanol percentage markings. The Fuel-Testers kit is available through Lakeside Marine, the national Tohatsu outboards importer and distributor and retails for $42.95 plus GST. Visit www.tohatsu.com.au or call Lakeside on (02) 4392 6110. I have used the kit for many batches of fuel since 2010 and am only halfway through the contents of that first Quik- Check bottle.

One issue that fortunately is not so common nowadays is adding toluene or dry cleaning fluid to fuel. In the days before toluene attracted a Federal Government excise some fuels from independent outlets were blended with this, enabling these outlets to make more profit per litre.
Unfortunately no kits exist for testing the presence of toluene, but a telltale sign is a pale blue colour, whereas 91 RON and 95 RON fuels have a pale straw colour. This is more prominent in 91 RON, making fuel levels in translucent plastic integral outboard tanks easier to see.
In my opinion petrol should never be bought on price alone, which is why I buy fuel from the major oil companies and not independents. Cruising yachties have the right to reliable auxiliary or tender power, guaranteed by good quality fuel.

Andrew Norton

M.O.S.S Australia
Nav at Home
Lagoon 51
M.O.S.S Australia
Nav at Home
West System Afloat