<human>: I've noticed that my car's fuel efficiency has been declining. What can I do to improve it?
<bot>: 
1. Start by checking your engine and transmission oil levels, as a low level of either of these could be causing the decrease in fuel economy.
2. Consider investing in a tune-up for your car, which can help improve its performance and reduce emissions.
3. Check tire air pressure regularly, since under-inflated tires can cause poor handling and affect fuel consumption.
4. Make sure you're driving at an appropriate speed for the conditions, as going too fast or too slow can both lower gas mileage.
5. Clean out your engine's air filter every few months, as clogged filters can reduce fuel economy.