My car, a 1997 Oldsmobile Cutlass, has such varying gas mileage! On the highway, i get up to 30 mpg, but when I drive around the city, it goes down to about 13 mpg. This has only happened over the last 18 months, when I inherited the car from my grandfather, who only used it to drive to the grocery store in Florida. Now I am in upstate New York, so the weather is quite different and the car is experiencing winter weather for the first time. Any idea what’s causing my mileage to fluctuate so much?
Does the engine come up to normal temperature reasonably quickly?
It could be a sticky thermostat, especially if it’s over 4 years old.
In city driving the engine doesn’t work hard and it might not be warming up fully if the thermostat doesn’t fully close.
Only careful measuring and filling at the same pump, same nozzle will give you an accurate reading. Having said that, I sincerely doubt you routinely got 30 mpg with a 1997 Olds Cutlass. That would be very lightfooted highway driving, almost no use of brakes and no A/C on.
Stop and go driving in cold weather in upstate New York with the car parked outside and no block heater and warming the car up for 10 minutes before driving off will definitely not give you more than 13 mpg.
In other words, these extremes are possible for reasons outlined, but you should go through several fillups AT THE SAME GAS PUMP, stopping at the first click. Where I live different gas companies set their pumps with a different click-off.
To improve your gas mileage from 13 mpg in upstate New York, install a block heater to come on 2 hours before you drive off. Park inside where possible, don’t let the car run for 10 minutes just to warm it up; gently drive off after 30 seconds, unless your windowss are totally frozen up.
As a comparison, I live near the Rocky Mountains and with a 1988 V8 Caprice achieved winter gas mileage of about 17.5 mpg by doing the above.
Do you give the car to someone else with a lead foot? If not, it’s probably because you drive in stop-and-go traffic in the city, but use the cruise control etc. on the highway.