[Phantom]

If you increase the compression by changing the stroke it will use more fuel since it will be a larger engine pulling more air in. Increasing the compression by shaving the heads, using thinner head/ lower end gaskets, or pistons would be the best way to do it.

As said before it should reduce fuel consumption if it does not significantly drop timing. With that said it could allow the use of larger gears or reduce the need of down-shifting when going uphill, and allow it to up-shift earlier with out lugging the engine.

Do your research on increasing the compression with your motor to see what issues you could run into. I assume that the engine has an over head cam so valve train geometry should not be a problem if shaving the heads or using thinner gaskets but could have valve to piston clearance issues.

What engine are you running?