Kindly let me know its fuel economy compared to, say, Toyota Wish 1800cc, acceleration and toggle issues, as well as the current resale value of the 2003 model.

You ought to use 5W30 fully synthetic or 10W40 semi synthetic reputable engine oil. These engines, at 80,000 -100,000 kms, tend to experience engine vibrations and loss of power at 500-600rpm.