Welcome,
If you haven't read these, do so.
100+ Hypermiling / ecodriving tips & tactics for better mpg - EcoModder.com
65+ Vehicle modifications for better fuel economy - EcoModder.com
If your car is carbureted, a vacuum gauge would be helpful. If injected a MPGuino.
Like mcrews said "Adjusting the nut behind the wheel" will give the best results.
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