well ever sense i have had bad luck with things always braking down on me on my VX or just simply time to replace alot of parts, i have tend to get in to the habit of constently watching and hearing everything my VX does or sounds. so i keep with the maint... all the time, i check everything i can possebly think of like 2-3 times a week and replace anything small and cheap all the time to keep the emissions and fuel consumptions as low as possible. well Thats my secret, i guess thats what have been improving my MPG, if not then i don't know, but i just suggest just to take care of your VX like if it's a real baby and keep it up to date all the time. chance the oil, and fluids, check the pcv valve, intake, temp's on oils, also it depands alot in your driving, not accelerating to fast unless you have to, and stuff like that. thats my guess, there is more, i just can't think of what else i do, oh allways fill up you tank to full, thats another thing i do.