The 1990 Jaguar Sovereign comes with a 4.0 liter fuel injected inline six cylinder (223 hp / 278 lb-ft) mated to a 4-speed automatic transmission with RWD. The curb weight (empty) is 3,903 lbs. But with me driving and the tank full it jumps to 4,251 lbs. So, what kind of fuel economy does a two ton Jaguar return? According to the government, I should expect 15 city and 20 hwy every time I fill the 22.8 gallon tank.
At first, I was mesmerized by the 30+ mpg reading of my trip computer. But after finding a TSB in AllData, I found out that the trip computers were noted for being inaccurate. So, I did it the old fashioned way. At every fill-up, I wrote down the odometer mileage and got the following results:
As you can see, I’ve been a bit impatient in trying to figure out the mileage. I’ve been filling it up when the fuel gauge reads 1/2. So, the fuel economy might be even better if I were to wait until the tank is almost empty.