I had and sold a 1990 LS400. Undoubtably the best car i will ever own. The 1990s have 18 gallon tanks and i got about 355-370 miles per 18 gallon tank on in town driving. It had 280,000 miles. My 1994 with 175,000 miles has a 20 gallon tank and i get no better than 265 miles to the tank. the...