[Vwdiesel] Better mileage?

[Libbybapa at wmconnect.com]

Two years ago my 1.6NA jetta was my daily driver.  I was putting 12+k miles 
on it per year.  The average mpg was 49.  Several tanks of fuel (mostly 
highway) got 52+.  I changed my employment position and now primarily drive a van.  
The jetta is now primarily a family car/errand runner/wife's car.  The mileage 
now with mixed driving is now mid to high 30's.  I think we are now probably 
below 5k miles per year.  The fillups are much farther apart in time, not as 
far in miles. Somewhat disappoining.  My imagination says that the I need to 
degunk the combustion chambers,ring grooves especially, so the seat more 
properly.  The pump is adjusted what seems relly nicely.  Good performance-liitle to 
no smoke.  Any recommends on products to use to degunk?
Andrew