Poor Fuel Economy
A sudden drop in mpg often comes from low tire pressure, a dirty air filter, a faulty O2 sensor or misfires.
Can I drive it? Safe to drive
Safe to drive. Check tire pressure and the air filter first.
Typical repair cost
$0 for tire pressure, $20-$60 for an air filter, $150-$400 for an O2 sensor.
General US estimates, not quotes. Prices vary by region, vehicle and shop.
Symptoms to Look For
These signs indicate you might be experiencing this issue
- Significant drop in miles per gallon
- Frequent fill-ups required
- Strong gasoline smell near vehicle
- Black smoke from exhaust
- Reduced engine power
Potential Causes
Most likely reasons for this problem, sorted by probability
Repair Solutions
Step-by-step instructions to diagnose and fix the problem
1Fuel System Maintenance
- 1
Replace air filter (usually behind black plastic box)
- 2
Add quality fuel injector cleaner to gas tank
- 3
Check and adjust tire pressures to spec
- 4
Replace spark plugs if overdue
- 5
Use scan tool to check oxygen sensor readings
Need professional help?
Find a repair shop near you, or describe your exact symptoms to the AI mechanic
When to See a Mechanic
Do not wait if any of these apply
- MPG drops sharply
- The check engine light is on
- A fuel smell
How to Prevent It
Simple habits that stop this problem coming back
- Keep tires inflated to spec
- Keep up with scheduled maintenance
- Remove roof racks and extra weight
Frequently Asked Questions
How much can tire pressure affect mpg?
Underinflated tires can cost a few percent of mpg. Checking pressure is the cheapest fix.
Does premium fuel improve mpg?
Only if your engine requires or is tuned for it.
Related Trouble Codes
Codes a scan tool may show with this problem
Related Issues
AI-generated and informational only. This is not a diagnosis of your specific vehicle and does not replace inspection by a qualified technician.