Gear test


thready compounds typically found in cases of diesel bug they will quickly accumulate, blocking the fi lter and slowing the passage of fuel, while other less tenacious contamination will pass through. Hence samples which passed slowly through the second fi lter would be likely to block the fi lter entirely over time.


We fi ltered 500ml of treated fuel through a 10 micron fi lter


This makes the test a more


accurate assessment of whether life still exists, as cATP can only exist in living cells while the free ATP will survive after the cells have been destroyed. We carried out the cATP test


twice on each sample – once after 24 hours and again after 10 days. Each day of the test the bottles were agitated briefl y, as even on a moored boat the fuel will not be completely static, then left to settle again. During the test the bottles were stored in the dark, as light is excluded from most boat fuel tanks and its presence can accelerate microbial growth.


TESTING FOR FILTRATION After we had completed the cATP testing, we used 500ml of each sample to check how effective the treatment had been at reducing the build-up of sludge that can block your fi lter. Boat fuel fi lters typically range in size from 5 microns to 30 microns, so we chose an intermediate value of 10 microns. To see how easily the fuel would


pass through the fi lter we agitated the sample and fi ltered it twice at 10 microns. The fi rst pass removed inorganic and particulate matter, leaving the treated fuel. We timed the second pass through a clean fi lter to show how easily the treated fuel will pass through it. This gives an insight into the type of contamination left in the fuel – if it is the colonies, emulsions and


UNDERSTANDING THE RESULTS The lower results graph on page 63 compares the initial cATP values with those after 10 days to give a measure of the effectiveness of the treatment over time, expressed as a percentage decline in cATP from the original fi gure. This should give a fair representation of how effective each treatment is in dealing with microbial activity, and removes any inconsistencies owing to variations of activity in each sample. The 24-hour fi gures, seen in the data panel for each product, vary in meaning according to whether the product is a biocide or an dispersant, so are not plotted as they can be misleading. However, low activity after 24 hours for a biocide suggests that it rapidly starts to kill the micro-organisms, while high activity for a dispersant product indicates that it quickly disperses colonies and lifts them into suspension – the key to this method of destroying diesel bug. The fi ltration data is compared


with the result obtained by running the same test with the untreated control sample to give a measure of how much faster treated fuel will pass through a fuel fi lter.


Checking


your tank If you don’t have a tank drain, try dipping a length of clear hose to the bottom of the tank. Then seal the top end with your thumb and transfer the contents to a jar for a good look. If the fuel is dark or shows sticky deposits, it needs treatment. Severely infected fuel smells of rotten eggs or varnish.


TEST KEY Bottle size: *indicates larger or smaller bottles available pg cATP/ml before/after: the amount of cellular ATP (in picograms) present in the fuel sample before the test, after 24 hours and after 10 days cATP reduction: Shows the percentage decline in the amount of microbial life over the 10 days, measured in cellular ATP Filtration results: improvement on control in fi lter test


Star Brite Bio Diesel


BIOCIDAL TREATMENTS – dehydrate Eradicate


Shock dose per litre: 0.3ml Shock dose cost per litre: 1.5p Maintenance dose p/lt: 0.3ml Maintenance cost per litre: 1.5p Bottle size: 473ml Bottle cost: £24.12 n www.starbrite.com CONTAMINATION


pg cATP/ml before: 42.57 pg cATP/ml after 1 day: 10.80 pg cATP/ml after 10 days: 5.69 cATP reduction: -87% FILTRATION RESULTS


Faster than control by: 44%


This product made a great start by doing 86% of its total work in the fi rst 24 hours. In the test fl ask there was no evidence of gummy deposits that block fi lters and for this reason our expert observed that the product would be benefi cial in cleaning your engine. However, the remaining microbial life and water in the fuel suggest that further treatment would be advisable.


Shock dose per litre: 1ml Shock dose cost per litre: 5p Maintenance dose p/lt: 0.5ml Maintenance cost per litre: 2.5p Bottle size: 1lt Bottle cost: £49.95 n www.bonnymans.co.uk CONTAMINATION


pg cATP/ml before: 14.51 pg cATP/ml after 1 day: 4.83 pg cATP/ml after 10 days: 0.45 cATP reduction: -97% FILTRATION RESULTS


Faster than control by: 44%


We used the lower dose for this test as Eradicate recommend the standard dose for all but the heaviest contamination. It proved highly effective, removing all but a few percent of microbial life and giving above average performance in the fi lter test. There were a lot of sticky deposits left in the bottom of the jar for which further treatment would be required to avoid fi lter blockage problems.


No gummy deposits, but water will need treating


Sticky deposits are an issue, but a good kill rate


Practical Boat Owner 534 May 2011 • www.pbo.co.uk


DIESEL BUG TREATMENTS TESTED


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