[bicyclerepair]

Here’s all I did to boost my mpg (helps boost power too)

K&N air filter (they guar a couple mpg)
Insulated air intake (outside air is cooler than under-hood air, thus denser with O2)
Low restriction exhaust
50psi low profile tires
Mobil 1 oil
Strut tower bar increases handling
Manual trans (+10%)
Leave backseats out

Believe it or not, this PT Cruiser can burn the tires off. And handles very well. Gets 32mpg on highway and high 20s around town. Exceptional for a PT Cruiser. And very fun to drive.

[Spktyr]

The K&N extracts a price in increased engine wear due to more particulates getting past the filter.

[American Constitutionalist]

Leave rear seats out ( front passenger seat if not needed 50 pounds right there ), carpet, door panels, back window deck, inner plastic fender well rain guards , hood sound insulator, trunk carpet, head liner.
That could reduce at least 100 pound right there alone.

[American Constitutionalist]

What I don't understand is why they don't make plastic hoods or truck lids for cars, unless they do that already.
I know they make plastic fenders for cars.
One thing that some people can do is reduce the weight of the engine by trying to see if their engine can be retro fitted with aluminium cylinder heads.
That there alone can reduce at least 50 to 75 pounds of weight.

[American Constitutionalist]

A front end alignment also helps in fuel economy because if the wheels are out of alignment there is friction from the tires.