, it’s interesting you mentioned the word darty. When I put 15mms spacer on the rear end of my car, the car immediately got squirrelly in corners – not good. Perhaps 15mm spacers were too much. But that slight change in suspension geometry had a very pronounced adverse effect on stability. I’m not sure why, but it seems our cars seem very sensitive to changes in offset.
, I had OEM 215/60-16s on my car for the last 50,000 miles. I did it solely for ride quality. Ride quality improved dramatically. Handling decreased very slightly. The stealth factor increased exponentially. With such boring wheels on my V6-6MT Accord, it became almost invisible. With regard to increasing fuel economy, I’d say it added no more than 1.0 to 1.5 mpg. Part of that was less rolling resistance (215s verses 235s). Part was a more eco-designed tire tread and rubber compound (grand touring all season tires versus a high performance all season tires), and a small part was from shedding 10 pounds of spinning weight per corner.
On that subject, the 40 lbs total reduction of spinning weight could have no greater effect than reducing 70 pounds of “static weight from the frame.” At most, spinning wheel/tire weight has an effective ratio of 1.8X that of static “frame” weight. Losing 40 pounds of wheel weight is like having burned 70 pounds of gasoline, or about 2/3s of a tank. That’s certainly good for fuel economy, acceleration and braking, but not by very much.
I know you did not say this, but if you are buying new wheels solely for saving money at the pump, you’ll need to drive a long time to break even. If gas costs $3.50 per gallon and you improved your fuel economy by a whopping 3 mpg, from 40 mpg to 43 mpg, the new wheels cost $700, and X is miles driven:
• (X/40 mpg)($3.50) = (X/43 mpg)($3.50) + $700
• .0875X = .081395X + $700
• .00610X = $700
• X = $114,667 miles
If you could average 3 mpg more, you'd need to drive about 115,000 miles to break even. But perhaps more important to you, will 16’s fit over your brakes? I don’t think they will. I think the smallest you can go are 17s.