Thinking of getting my 170 TDi Quattro re-mapped, and to help justify the cost to myself then I think the fuel economy improves, is that right ? I'm doing about 18,000 miles pa, and currently averaging about 43mpg. If I were to get another, say 4mpg, then that would save me about 35 gallons a year, which is 160 litres, which at say £1.37 then about £220 per year. Is an extra 4mpg reasonably, or more or less ? Obviously I should tell the insurance about the re-map which will lose some of the savings, but over 2 or 3 or 4 years the cost of the re-map plus insurance should be covered if I get a few extra mpg. Thoughts ?