I have a 1992 es300 I bought and fixed for my wife. Has 200,000 miles on it but it starts and runs great, a minor oil leak. The car has never gotten better than about 21mpg even on highway. To pass emissions I had to replace every vacuum line and hose on it and give it a tune-up. Timing is spot on. Can anyone tell me what I should expect to get on the Highway (mpg) within reason. I think that 21mpg is way to low for highway? Any help or recomendations?