Secondary Air Injection Pump Failure
high- Typically appears
- 70–100k mi
- Estimated repair
- $900 – $1,400
2021 Toyota
4RunnerSUV
SUV
The 2021 Toyota 4Runner is a fifth-generation body-on-frame SUV that has changed very little since its 2010 redesign — and that's largely a feature, not a bug. It's built around a proven 4.0L V6 paired with a 5-speed automatic, a combination Toyota has refined into near-bulletproof reliability. The 4Runner is one of the few remaining SUVs that can genuinely go off-road without modifications, thanks to a solid rear axle, generous ground clearance, and available locking rear differential and crawl control. What you give up is fuel economy and modern tech refinement. At 17 mpg combined, it's thirsty by any standard, and the infotainment system feels a generation behind competitors. The ride on pavement is truck-firm. But buyers who choose a 4Runner aren't trading it for a crossover — they want something that will haul the boat, handle the logging road, and still be running strong at 250,000 miles. In the upper Midwest, the 4Runner has a strong following for good reason: it handles Wisconsin winters well, the 4WD system is confidence-inspiring on packed snow, and the body-on-frame construction holds up to years of abuse better than unibody competitors. Frame rust is a legitimate concern in the salt belt and should be addressed proactively.
Reliability
5/5
Verified data
Specs shown for 4Runner 2WD — the most common configuration.
Other trims may vary in engine, drivetrain, or fuel economy. Sign in to see your vehicle's exact specs.
Engine
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Drivetrain
RWD
Fuel
Gasoline
MPG
16 city / 19 hwy / 17 combined
Seats
—
Doors
—
Body
Standard Sport Utility Vehicle 2WD
Length
190.2 inches
Overview
AI-curatedThe 2021 Toyota 4Runner is a fifth-generation body-on-frame SUV that has changed very little since its 2010 redesign — and that's largely a feature, not a bug. It's built around a proven 4.0L V6 paired with a 5-speed automatic, a combination Toyota has refined into near-bulletproof reliability. The 4Runner is one of the few remaining SUVs that can genuinely go off-road without modifications, thanks to a solid rear axle, generous ground clearance, and available locking rear differential and crawl control. What you give up is fuel economy and modern tech refinement. At 17 mpg combined, it's thirsty by any standard, and the infotainment system feels a generation behind competitors. The ride on pavement is truck-firm. But buyers who choose a 4Runner aren't trading it for a crossover — they want something that will haul the boat, handle the logging road, and still be running strong at 250,000 miles. In the upper Midwest, the 4Runner has a strong following for good reason: it handles Wisconsin winters well, the 4WD system is confidence-inspiring on packed snow, and the body-on-frame construction holds up to years of abuse better than unibody competitors. Frame rust is a legitimate concern in the salt belt and should be addressed proactively.
Known for
- Exceptional long-term reliability from the 4.0L V6
- Genuine off-road capability with solid rear axle and high ground clearance
- Strong resale value — one of the best in its class
- Body-on-frame construction that outlasts most modern SUVs
- Outdated but simple infotainment and interior tech
Best for
- Buyers who want a capable off-road or adventure vehicle
- Owners who prioritize longevity over luxury or fuel economy
- Towing light loads (up to 5,000 lbs) on varied terrain
- Wisconsin winters and rural driving conditions
- Buyers planning to keep the vehicle 10+ years
Watch for
- Poor fuel economy — budget for premium gas costs over time
- Frame rust in salt-belt states; inspect and undercoat proactively
- Secondary air injection pump failure around 80k miles
- Infotainment is slow and dated compared to competitors
- Transmission rough shifting if fluid service has been neglected
Common issues by mileage
6 knownTransmission Rough Shifting / Hesitation
medium- Typically appears
- 50–90k mi
- Estimated repair
- $200 – $3,000
VVT-i Oil Lines Leaking or Sludging
medium- Typically appears
- 80–150k mi
- Estimated repair
- $300 – $800
Frame Rust (Salt Belt)
high- Typically appears
- 60–150k mi
- Estimated repair
- $500 – $3,000
A/C Compressor Failure
low- Typically appears
- 90–130k mi
- Estimated repair
- $700 – $1,400
Torque Converter Clutch Performance Issue
low- Typically appears
- 60–100k mi
- Estimated repair
- $1,500 – $3,500
Maintenance schedule
- 1 Every 5,000 miles or 6 months Engine Oil Change — 0W-20 Full Synthetic, 6.6 qts with filter
Toyota specifies 0W-20 synthetic. In Wisconsin's cold winters, this low-viscosity oil flows fast on cold starts, protecting the VVT-i system which is sensitive to oil quality and change intervals. Skipping this accelerates VVT sludge issues.
- 2 Every 60,000 miles Transmission Fluid Service — Toyota WS ATF, 11.3 qts total
Toyota markets WS fluid as 'lifetime,' but independent shops in the Midwest routinely see rough-shifting 4Runners that have never had a fluid change. Changing at 60k prevents the solenoid wear and clutch pack degradation that leads to expensive repairs.
- 3 Every 30,000 miles or when subjected to water crossings Differential and Transfer Case Fluid Service
Front and rear differentials use 75W-85 GL-5; transfer case uses 75W GL-4. Off-road use or water crossings can contaminate fluid. Contaminated gear oil accelerates bearing and gear wear — cheap insurance on a $40k vehicle.
- 4 Every 30,000 miles Air Filter Replacement (Part 17801-35020)
Gravel roads and off-road use load the filter faster than city driving. A clogged filter reduces power and fuel economy, and in very dirty conditions can stress the MAF sensor.
- 5 Every 20,000 miles Cabin Air Filter Replacement (Part 87139-52020)
Wisconsin pollen and road dust clog cabin filters quickly. A restricted filter strains the blower motor and reduces defrost effectiveness — critical for winter visibility.
- 6 Every fall before salt season Undercarriage Inspection and Rust Treatment
Frame rust is the 4Runner's single biggest threat in the salt belt. Inspect the frame rails, crossmembers, and brake lines annually. Address surface rust early; penetrating rust on brake lines or the frame is a safety issue and far more expensive to fix late.
- 7 Every 2–3 years regardless of mileage Brake Fluid Flush — DOT 3
DOT 3 is hygroscopic — it absorbs moisture over time, lowering its boiling point and accelerating corrosion in the ABS modulator. Wisconsin temperature swings make this more relevant than in mild climates.
- 8 First change at 100,000 miles, then every 50,000 miles Coolant Service — Toyota Super Long Life (Pink)
Toyota SLLC is genuinely long-lived, but do not mix with green or orange coolant — it degrades the protection chemistry. Capacity is 10.4 qts; always pressure-test the system when servicing.
Always defer to the manufacturer's service manual for warranty-mandated intervals.
Cost of ownership
Annual maintenance
$600 – $1,200
Fuel
At 17 mpg combined and ~15,000 miles/year, expect roughly 880 gallons annually. At $3.40–$3.80/gallon in the Lake Geneva area, budget $3,000–$3,350/year in fuel. The 4Runner uses regular 87 octane.
Insurance
Typically $1,400–$1,900/year in southern Wisconsin for a 2021 model, depending on driver history and coverage level. High resale value pushes comp/collision premiums slightly above average for the segment.
The 4Runner's routine maintenance costs are modest for its size — oil changes, filters, and fluid services at an independent shop run $600–$1,200/year in normal operation. The big wildcard is a secondary air injection pump failure ($900–$1,400) or transmission repair ($1,500–$3,500) if fluid service has been deferred. Fuel is the largest ongoing expense. On the flip side, depreciation is extremely low — the 4Runner holds value better than almost any other SUV, which partially offsets higher running costs over a long ownership period.
Seasonal care
Lake Geneva, WI Winter
- Switch to a dedicated winter tire set — the 4Runner's all-terrain or highway tires do not substitute for a proper winter tire in sub-zero temperatures. Mount on a spare set of steel wheels to save the alloys from salt damage.
- Test the battery before November. Cold cranking a 4.0L V6 at -10°F demands a healthy battery. If the battery is 4+ years old, replace it proactively — a dead battery in a Lake Geneva winter is not a small inconvenience.
- Fill the washer fluid reservoir with -20°F or -40°F rated fluid. The 4Runner's large windshield and high driving position mean constant road spray; standard fluid will freeze in the lines.
- Inspect brake lines and rubber brake hoses during fall undercarriage check. Salt accelerates line corrosion; a leaking line at highway speed is dangerous.
- Engage 4WD periodically even if conditions don't require it — letting the system sit unused all winter can cause engagement issues with the vacuum-actuated front differential.
- Rinse the undercarriage every 10–14 days during active salting periods. A coin-op touchless spray is sufficient; focus on frame rails, wheel wells, and exhaust hangers.
Summer
- Check tire pressure after the first warm weeks of May — pressure rises about 1 PSI for every 10°F increase in ambient temperature. The 4Runner's recommended pressure is 32–35 PSI depending on load.
- Inspect and recharge the A/C system if cooling is marginal. The 4Runner's A/C compressor has a known failure pattern around 100k miles; catching low refrigerant early protects the compressor.
- Inspect the coolant level and condition before summer road trips. The 4.0L runs warm under towing loads; a weak cooling system shows up quickly when pulling a boat up a hill in July.
- Check the power steering fluid level — the 4Runner uses conventional hydraulic power steering, which can develop small leaks at the rack seals over time and is easy to miss until the pump whines.
Comparable vehicles
2021 Ford
Bronco
Body-on-frame off-road SUV in the same price range. More modern interior and tech than the 4Runner, similar off-road credentials. Less proven long-term reliability track record at this point.
2021 Jeep
Wrangler Unlimited
The other benchmark for body-on-frame off-road SUVs. More off-road capable out of the box in some configurations, but significantly higher ownership costs and lower reliability scores than the 4Runner.
2021 Chevrolet
Tahoe
If the priority is towing capacity and passenger space over off-road use, the Tahoe offers more of both. Higher running costs and softer resale value compared to the 4Runner.
2021 Nissan
Xterra
Direct off-road segment competitor — though Xterra production ended in 2015, used examples compete directly with the 4Runner in the used market at a lower price point with similar body-on-frame durability.
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