You might be making a mistake going with the spare wheel. Here is my thread where I tried out using my usual tires on a 14x4 wheel:
http://ecomodder.com/forum/showthrea...hts-32033.html
It wound up hurting my fuel economy by increased weight and rolling resistance. There is also another thread located somewhere on here in which Darin (MetroMPG) did ABA testing on coastdown times with different air pressures. He used spare wheels and tires in a run and they failed miserably. Donkey CRX runs the Insight spare wheels on 165 width tires and has had zero problems with them. He gained mpg over the stock VX wheel IIRC.
What is your stock tire size? If it is thin enough, you can run spare wheels and not have the issues I did.
Also, the Insight spare wheels are an alloy, so they are uber light. I'd say less than 5 kilos each. If the spares are steel, you may not gain any weight loss.
Btw, welcome to Ecomodder
