NHTSA lists 1 safety recall and 3 owner complaints for the 2004 Mitsubishi Diamante. Most complaints involve power train (3). The EPA rates it 18 mpg combined.
CERTAIN PASSENGER VEHICLES FAIL TO CONFORM TO THE REQUIREMENTS OF FEDERAL MOTOR VEHICLE SAFETY STANDARD NO. 208, 'OCCUPANT CRASH PROTECTION.' THE BILINGUAL ENGLISH/SPANISH REMOVABLE AIR BAG WARNING LABELS AFFIXED TO THE DASH AND TO THE SUNVISOR DO NOT MEET THE SIZE REQUIREMENTS OF THE STANDARD.
Complaints are unverified owner reports to NHTSA and are not normalized for sales volume. One complaint can cite several components.
“THE DIAMANTE HAS AN ODD ISSUE WHERE THE VEHICLE WILL NOT SHIFT GEARS CORRECTLY WHICH AN EXTREMELY DANGEROUS ISSUE FOR DRIVERS. THE INFORMATION BOARD SHOWS THE TRANSACTION RAPIDLY SWITCHING FROM NEUTRAL TO DRIVE EXCESSIVELY. I HAVE HAD MULTIPLE MECHANIC SHOPS LOOK INTO THIS ISSUE FROM TRANSMISSION SPECIALISTS, TO ELECTRICAL SPECIALIST AND HAVE HAD NO POSITIVE RESULTS.”
Towing, payload and dimensions aren’t in the EPA or NHTSA data, so we don’t list them.
| Version | City | Hwy | Comb. | Fuel / yr | CO₂ g/mi |
|---|---|---|---|---|---|
| Diamante Sedan Auto (S4), 6 cyl, 3.5 L · Front-Wheel Drive | 15 | 23 | 18 | $4,200 | 494 |
| Diamante Sedan Auto 4-spd, 6 cyl, 3.5 L · Front-Wheel Drive | 15 | 23 | 18 | $4,200 | 494 |
| Item | Miles | Time | Note |
|---|---|---|---|
| Engine oil & filter | 5,000–10,000 mi | 6–12 months | Follow the oil-life monitor if fitted |
| Tire rotation | 5,000–7,500 mi | Every oil change | Check pressure monthly |
| Engine air filter | 15,000–30,000 mi | 1–2 years | Sooner in dusty areas |
| Cabin air filter | 15,000–25,000 mi | 1–2 years | |
| Brake fluid | — | 2–3 years | Absorbs moisture over time |
| Coolant | 60,000–100,000 mi | 5–10 years | Long-life coolants last longer |
| Spark plugs | 60,000–100,000 mi | — | Iridium/platinum plugs at the long end |
| 12V battery | — | 3–5 years | Heat shortens battery life |
1 safety recall as of Nov 13, 2026, according to NHTSA. Recall repairs are free at a dealer. Check your VIN to see whether your car is included and whether the repair was done.
Owners filed 3 complaints with NHTSA. The most-cited components are power train (3). Complaints are unverified owner reports and aren't adjusted for how many cars were sold.
The EPA rates the 2004 Mitsubishi Diamante at 18 mpg combined, depending on engine and drivetrain (2 versions rated).