Wednesday, 14 August 2013

Fuel Economy

You can probably figure out your car's fuel consumption. Fill up and zero the trip meter. Next time you fill up, note the amount of fuel in gallons required to fill up the tank. Then divide the trip mileage by the amount of fuel added.  That's your MPG figure. However, it's a different story calculating and quantifying a boat's fuel consumption.

Fuel has come down a bit in price. 91p a litre was the last price we paid  (no self declaration needed) as I topped up the fuel tank. Now I am experimenting and trying to improve the hours per litre figure. Increasing your fuel efficiency saves you time and money with fewer trips to the diesel pump.

Prior to trying to save fuel, I spent almost a year measuring distance travelled against fuel used. I then found it was better and easier to understand if I calculated the fuel per hour consumption. Which in our case averaged out at (1h:28m) or around one and a half hours per litre of fuel.

Things that can affect fuel economy:

Fast acceleration by revving the engine hard will consume additional fuel. A more leisurely and steady build up of speed will require less energy and therefore the engine will consume less fuel.

You can't rush anywhere on a boat, you will waste large amounts of fuel in trying. Get into the fuel conservation mode of boating it becomes much more leisurely and enjoyable. Reducing engine speed and then cruising to a stop rather than maintaining speed until the last moment and then using the engine in reverse can also help to save fuel.

Even when idling in neutral, your boat is consuming fuel. There is a trade off between, pausing for a few moments on tick over and continuing to run the engine for longer periods, such as when locking. I don't always stop the engine in a lock. It depends on the size of the lock and how long it will take to fill or empty and whether I can get a line on a bollard. If I get in a queue at a lock the engine is always off until its my turn.

Throttle back slightly and find the speed where the motor is running smooth without effort whilst maintaining a constant speed.  You will need to adjust the throttle from time to time as the width and depth of water varies. Reducing speed by 10% can save quite a bit of fuel. Water flow under and round the boat on a deep wide stretch of water is effortless. However in the narrower and shallower regions the engine will come under increased load. It will be necessary to adjust the boats speed through the water to minimise fuel consumption.

A worn engine is not fuel efficient, so it is essential to service the engine at recommended intervals. A well maintained engine is serviced on schedule and will in return give a long service life. It is false economy to skip or extend service intervals. Some marine engines have a reduced sump size and so therefore need more frequent servicing.

I am not a believer is using additives in the engine oil. The correct grade and type of oil will give a good service life. However, I am a believer in using additives to the fuel to stop diesel bug from developing. Never wait for it to start, be proactive and use suitable additives before it occurs. Keeping your boat's tank full helps prevent condensation and the accumulation of water in the diesel. This water will promote organic growth, which will degrade your fuel and affect fuel economy.

This one is a bit hard to quantify, but the harder an alternator is working the greater the load on the engine. We have to run the engine whenever we run the washing machine on the boat. The battery bank and the alternator together can manage to run the washer for a couple of wash cycles. I always time the wash for a cruising day. I let the alternator top up the batteries for half an out before the first wash is done.

Sometimes you will need to run the engine to charge up the battery bank. Fitting solar panels can give a useful top up to the battery bank. Therefore requiring reduced charging time by the engine. We have three solar panels. In 14 months the controller has measured over 10,000ah being added to the battery bank. That is the equivalent of recharging the battery bank to full capacity 20 times.

Fuel economy also applies to your pocket. So shop around for fuel, because prices can vary by a large amount.  I have had recent fill up prices that range between 85p to 120p per litre. Some suppliers are also enforcing a fixed split charge, rather than the usual self declare method. Only use proper outlets as some people sell distilled corn oil and chip fat as 'Red Diesel'.


1 comment:

  1. Whilst I agree with some of that I cant agree with all of it.

    We often dont get the choice of shopping around. If we are away on holiday and need fuel we have to buy it where it is avaliable. For example last month when we pulled into Lowestoft we needed fuel there and then. It was pricey but we needed it.

    We dont use fuel additives. We have found that using our fuel rather than storing it is all the rpeventitive measures that we need. We have no sign of bug in our filters or tank.

    Boating isnt a fuel efficient way of life and trying to make it fuel efficient is a losing battle. Our average fuel economy over the last five years is around the 5mpg mark, not great really


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