MK3 milage

[Genos]

Hello all, my '97.7 Jetta on the last tank went about 460 miles& I filled her up, think I got about 39.4 mpg, mostly city driving. Checked pump timing w/Ross-Tech,dead-on middle of graph. Set EGR duty cycle.Last tank I think I was about 42 mpg, Is this normal variation, colder weather coming, more warm-up time,etc? I put a head on her a couple thousand miles ago, no problems, engine temp seems a little low, 165-170F,should change t-stat?anything else to get more mpg? cars a great runner, starts fast no issues,has 5-speed. Would 15 inch tires help? Wish it was 5-bolt rims,is it possible to change hubs?. thanks Genos

[Seatman]

Hello, A lot of people over here in the UK change their hubs for the five stud on various vags but you can also buy adapters. I don't think the tyres would make much difference personally but I could be wrong. Your mpg seems a bit low if it's a 1.9tdi. Is there a chance of miss calculation?