Polishing is a term given to the process of chemically manipulating the molecular structure of a chemical compound to give a predictable and consistant resultant compound. When refered to fuel it usualy means that impurities are converted to a state where they will burn regularly and without the emissions usualy associated with the untreated fuel.
In answer to your second question, it's unlikely you will find an apreciable increase in speed. However you may experience a slight reduction in fuel consumption and smoke emissions depending upon the adative you chose to add. Most of the addatives on the market concentrate on killing the dreaded fuel bug rather than polishing the fuel so it's worth reading the lables carefully so that you don't add the wrong stuff and then get dissapointed when you don't get the results.
I have used a polishing addative for about a year now and consumed approx 5000l of diesel and have indeed got beter fuel consumption (Approx 10%) and cut down on smoke emmissions. At the last filter change there was no sediment or sign of contamination. So I'm a convert. Best advice is buy some, try it and if it don't work don't buy any more.
ChrisP ;o)
<hr width=100% size=1>What do you mean the sea gull in front's walking !!!
I understood "Polishing fuel" meant that the fuel in the tank was continually filtered through a seperate filter system prior to it being fed to the normal engine filters. Also used to treat a tankful with an external pump and filters. Or so the Americans say...
<hr width=100% size=1>dickh
I'd rather be sailing... /forums/images/icons/smile.gif
Yep, thats what it means, pumping it round a secondary filter system to remove impurities. Normally three times total fuel tank capacity pumped round per hour.