In all my years of owning, wrenching and tuning with the LC2 I've found that the stock calibration will consistently get better fuel economy than anything modified. Not that you can't pick up mpg with a modified engine because you certainly can. Higher CR, less overlap, thinner rings, rounder bores, tighter ring gaps, tighter piston to wall, higher silicon content in Pistons, higher engine temps (190-205*), tires with less rolling resistance, etc. All these will increase efficiency a lot but will leave it prone to damage from detonation. Once you start to add overlap, use loose fitting pistons, 160 thermostat, tires with more rolling resistance, etc you will lose economy. Going from one chip to another isn't going to do much at all for economy if the cruising block learn is 128. Additionally most chips have less cruise timing than the stock chip. If you run any leaded fuel or any fuel additives that make the oxygen sensor lazy forget it. You will have lousy economy. With -8 overlap @ .050" and 8.3:1 CR and GN1 heads and PTC 9.5" converter I achieved 20-21mpg driven too and from Cecil county MD and I live in central CT. This included 3 low 10/high 9 passes. I'd bet it would have hit 22-23mpg without the idling and passes at the drag strip. 65mph cruise speed on the way. 15.3-15.5:1 cruise a/f. I didn't step on it at all except for the quarter passes. I don't really car about economy. If I did I wouldn't drive an 800hp car
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