Last January, a 2020 Subaru Outback owner headed to Big Bear for a weekend ski trip, confident that his Symmetrical All-Wheel Drive would handle any conditions. He'd checked the weather forecast showing clear conditions and figured his vehicle needed no special preparation beyond filling the tank. Thirty minutes past Running Springs on Highway 330, a sudden snowstorm moved through the mountains. His all-season tires with 5/32-inch tread struggled for traction, his standard wiper blades iced up within minutes leaving him nearly blind, and when CHP implemented chain controls, he had no chains to install. Officers directed him to turn around, and he lost his entire weekend reservation and $780 in wasted lodging and lift tickets. Proper winter preparation including winter tires, emergency equipment, and vehicle inspection? $650 for tires plus $145 for comprehensive winterization service, usable for the entire season and many mountain trips.
That Outback owner made a critical mistake common among Southern California Subaru drivers: assuming that all-wheel drive alone provides adequate winter capability. While Subaru's legendary AWD system is exceptional, it's only one component of winter preparedness. AWD helps you accelerate and maintain momentum on slippery surfaces, but it does nothing to improve braking or cornering beyond what your tires can provide. And if your tires can't grip ice and snow, even the best AWD system in the world can't overcome that fundamental limitation.
Ontario sits at just 980 feet elevation where temperatures rarely drop below 40 degrees, creating a false sense that winter preparation isn't necessary. But within 90 minutes, you can reach elevations above 7,000 feet where snow depths measure in feet, temperatures drop below zero, and conditions rival anywhere in the Rocky Mountains. The San Bernardino Mountains via Highway 330, Mountain High via Highway 2, or Big Bear via Highway 18 all present genuine winter conditions that demand proper vehicle preparation.
This comprehensive guide covers every aspect of winterizing your Subaru for mountain snow and ice, from essential tire selection to emergency equipment and vehicle service that ensures reliable, safe operation in conditions that test every system simultaneously.
Winter Tire Selection: The Most Critical Decision
Winter tires transform your Subaru's capability more dramatically than any other single modification or accessory. The improvement in traction is so substantial that winter tires should be considered mandatory equipment for regular mountain winter travel.
All-season tire limitations become apparent on snow and ice. All-season tires use rubber compounds engineered to work adequately across a wide temperature range, but this versatility requires compromises. Below 45 degrees, all-season tire rubber stiffens and loses the flexibility needed to conform to road surfaces. On snow and ice, all-season tires lose 30-50% of their grip compared to winter tires.
Your Subaru's AWD can only work with the traction your tires provide. If all four tires are sliding on ice, AWD makes all four slide equally—it can't create traction that doesn't exist. Winter tires provide the actual grip that allows AWD to demonstrate its capabilities.
Winter tire technology uses fundamentally different rubber compounds that remain flexible below 45 degrees, maintaining grip when all-season tires have stiffened. The rubber maintains its ability to conform to microscopic irregularities in pavement, snow, and ice that provide mechanical grip. This flexibility persists down to -40 degrees, ensuring effectiveness during the coldest conditions California mountains produce.
Tread pattern design in winter tires features aggressive blocks with thousands of thin slits called sipes. These sipes create additional biting edges that grip snow and ice mechanically. The pattern also includes larger voids between tread blocks that pack with snow—snow sticks to snow better than anything else, creating excellent traction. All-season tires lack this aggressive siping and have shallower voids optimized for rain, not snow.
Winter tire performance gains are dramatic and measurable. Independent testing shows winter tires provide 30-50% better braking on snow, 25-40% better acceleration on ice, and substantially improved cornering stability compared to all-season tires. These improvements mean stopping 30-50 feet shorter from highway speeds on snow—potentially the difference between controlled stops and accidents.
For Southern California mountain driving, winter tires are the single most effective safety upgrade available. They're more important than chains (which you'll still need to carry for chain control requirements), more effective than AWD by itself, and provide capability that simply cannot be matched by all-season tires regardless of brand or tread depth.
Tire selection for Subaru models depends on your vehicle and typical mountain destinations. For Outback, Forester, Crosstrek, and Ascent models heading to Big Bear, Mountain High, or Mammoth regularly during winter, a complete winter tire set on dedicated steel wheels is the optimal solution. This allows easy seasonal swapping while preserving your all-season tires during winter months when road hazards increase.
Bridgestone Blizzak, Michelin X-Ice, and Continental WinterContact are three top-tier winter tire lines that deliver excellent performance in California mountain conditions. All three maintain flexibility in extreme cold, provide excellent snow and ice traction, and wear reasonably for winter tires (40,000-50,000 miles). Cost: Complete set of four winter tires mounted on steel wheels $650-950 depending on tire size.
Installation timing should be early November, before the first significant mountain snowfall. Historical weather patterns show Big Bear's first measurable snow typically arrives between November 15 and December 5, so early November installation provides a safety margin. Remove winter tires in late March or early April when mountain snow season ends.
"The difference between all-season and winter tires is so dramatic that first-time winter tire users often think we've somehow improved their vehicle's AWD system," says David Martinez, Service Manager at our Auto Center Drive location. "We haven't changed anything except the tires, but the traction improvement is so substantial that their Subaru feels like a completely different vehicle on snow and ice. Customers who make one winter mountain trip on all-season tires, then try winter tires the following season, never go back. The confidence and safety margins winter tires provide aren't subtle—they're transformational."
Essential Winter Emergency Equipment
Even properly prepared vehicles can encounter situations requiring emergency equipment. Mountain weather changes rapidly, and having the right supplies transforms potential disasters into manageable inconveniences.
Tire chains are legally required during chain control conditions in California mountains, regardless of whether you have AWD or winter tires. CHP implements chain controls on Highway 330, Highway 18, Highway 2, and Interstate 15 during and after winter storms. Without proper chains, you'll be turned around at checkpoints, wasting your trip.
Cable chains represent the best option for most Subaru owners. These use steel cables instead of traditional chain links, making them lighter, easier to install, and less likely to damage wheel wells. Quality cable chains like Security Chain Company Super Z6 or Konig K-Summit cost $80-140 per pair and are substantially easier to install than traditional link chains.
Purchase chains sized specifically for your tire size—check the sidewall for the size designation (like 225/65R17) and match chains to that exact size. Chains that are too large won't provide adequate traction, while chains too small won't install or can damage tires.
Practice chain installation in your driveway before you need them on a mountain road. The process seems simple until you're doing it in 20-degree weather with frozen fingers while traffic backs up behind you. Fifteen minutes of practice at home makes actual installation take 5-10 minutes instead of 30 frustrating minutes in the snow.
Emergency supplies should be stored in your Subaru year-round if you make regular mountain trips:
Safety and communication: Flashlight with extra batteries, reflective warning triangles, high-visibility vest, fully charged portable phone charger, emergency whistle.
Vehicle emergency tools: Portable jump starter (lithium-ion models can start your Subaru multiple times and fit in the glove box), tire pressure gauge, basic tool set, duct tape, tow strap rated for your vehicle weight.
Winter-specific items: Ice scraper and snow brush (heavy-duty models for mountain conditions), small folding shovel for digging out, traction aids like sand or cat litter, traction boards for getting unstuck, lock de-icer spray.
Survival supplies: Blanket or emergency sleeping bag rated to 20°F (temperatures in mountain areas can drop well below this), work gloves, bottled water, high-energy snacks, hand warmers, first aid kit.
Pre-assembled emergency kits cost $120-180 for comprehensive packages, or assemble individual items for $80-140. Store supplies in a durable container in your cargo area where they're accessible but won't shift during driving.
Communication and navigation take on critical importance in mountains where cell service can be spotty. Download offline maps in Google Maps or similar apps for areas you'll be traveling through. Carry a car charger or portable battery pack to ensure your phone stays charged. Consider a satellite communicator like Garmin inReach ($250-450 plus subscription) if you frequently travel to remote mountain areas with no cell coverage.
Critical Vehicle Service Before Mountain Travel
Several service items must be verified and addressed before mountain winter driving, as conditions stress systems beyond what sea-level California driving demands.
Battery testing and replacement becomes critical because cold reduces battery capacity by 35-60% while simultaneously your engine requires more power to start. A battery that cranks your Subaru fine in 70-degree Ontario weather might barely turn the engine at 25 degrees in Big Bear. If your battery is over 3 years old or tests below 75% capacity, replace it before mountain winter travel. Cost: Battery testing $25-40, battery replacement $185-240.
Coolant system inspection and service ensures your cooling system can handle sustained grades and provides adequate freeze protection. Mountain driving means extended uphill climbs generating far more heat than level driving. Simultaneously, overnight temperatures in mountain areas can drop below zero, requiring adequate antifreeze protection.
Pressure testing reveals leaks that aren't obvious during normal driving but will worsen under stress. Coolant freeze protection testing verifies your mixture protects to at least -20°F. Hose inspection catches deteriorating components before failure. Cost: Pressure testing $40-60, coolant service if needed $140-180.
Brake system comprehensive evaluation measures pad thickness, rotor condition, and brake fluid moisture content. Mountain driving requires extensive braking during descents, generating tremendous heat. Brake pads below 4mm thickness won't survive mountain trips, and moisture-contaminated brake fluid can boil during extended downhill braking.
Brake fluid service is particularly critical before mountain travel. Fresh fluid with low moisture content resists boiling even during demanding use. Subaru specifies brake fluid replacement every 3 years—if your fluid is approaching this interval, complete service before mountain trips. Cost: Brake inspection typically free with service, fluid service $120-160, pad replacement $350-550 per axle if needed.
All-wheel drive system should be verified as operating correctly through diagnostic scanning and test drive evaluation. Modern Subaru AWD systems include electronic controls and multiple sensors. Any problems affect traction distribution precisely when you need maximum capability. Cost: AWD system diagnostic check $120-150 if problems are suspected.
Windshield and wiper system must function flawlessly during snow and ice. Standard wiper blades fail in winter because their exposed frame freezes, preventing proper flex. Winter wiper blades use beam design with rubber boots covering the entire structure, preventing ice buildup. The rubber remains flexible below zero degrees. Cost: Winter wiper blades $35-60 per pair.
Understanding and Using Your Subaru's Winter Features
Modern Subarus include several features specifically designed for winter conditions. Understanding how to use them maximizes your vehicle's capability.
X-MODE (available on Outback, Forester, Ascent, and some other models) optimizes AWD power distribution, engine power delivery, and transmission shift points for challenging traction conditions. The system adjusts how aggressively AWD distributes power between wheels and modifies throttle response to prevent wheel spin.
Activate X-MODE before you need it—when you're about to encounter snow, ice, or steep grades. The system works best when engaged proactively rather than reactively after you're already struggling. X-MODE has different settings (Snow/Dirt and Deep Snow/Mud on some models) optimized for specific conditions. Use Snow/Dirt mode for typical winter mountain driving.
Hill Descent Control maintains steady, controlled speed during steep descents without requiring constant brake application. This prevents brake overheating during extended mountain descents and provides smoother control than manually managing speed. Activate hill descent control before beginning major downhill grades, setting your desired speed (typically 5-15 mph depending on conditions).
Vehicle Dynamics Control (VDC) and traction control work together to maintain stability and prevent wheel spin. These systems operate automatically, but you should understand when they're intervening. If you feel the VDC activate frequently (pulsing through the brake pedal, flashing VDC light, or slight reduction in power), you're operating near traction limits and should reduce speed.
The VDC OFF button allows you to disable stability control in specific situations where wheel spin is actually helpful—like getting unstuck from deep snow. However, leave VDC active during normal winter driving, as it provides critical safety margins.
Heated seats and heated steering wheel (if equipped) provide comfort that improves safety by keeping drivers alert and comfortable. Cold drivers become distracted and uncomfortable, reducing their focus on driving. Use these features liberally during mountain travel—they draw relatively little power and substantially improve comfort.
Mountain Driving Techniques for Maximum Safety
Even properly prepared Subarus require appropriate driving techniques to maximize safety margins during mountain winter travel.
Speed reduction is mandatory on snow and ice regardless of your vehicle's capabilities. Physics dictates that stopping distances on snow can be 3-4 times longer than dry pavement, and ice can extend stopping distances 5-10 times. AWD helps acceleration but doesn't improve stopping—only reduced speed and proper technique accomplish that.
Reduce highway speeds to 40-50 mph on snow-covered roads, and 20-30 mph on ice. These speeds seem painfully slow but provide the safety margins that prevent accidents. Remember that speed limits posted on mountain roads assume dry conditions—reduce appropriately for actual conditions.
Following distance must expand dramatically on slippery surfaces. The 3-4 second following distance adequate in dry conditions should increase to 8-10 seconds on snow and ice. This provides adequate distance to stop safely and gives you time to observe and react to vehicles ahead losing control.
Smooth inputs prevent loss of traction that abrupt actions cause. Accelerate gently, brake progressively, and steer smoothly. Sudden acceleration causes wheel spin even with AWD. Abrupt braking can lock wheels despite ABS. Quick steering inputs can break traction and cause skids. Treat every control input gently and progressively.
Engine braking during descents reduces brake system stress during long mountain downhill grades. Use your transmission's manual mode (if equipped) or shifter to select lower gears that allow the engine to help control speed. This reduces brake heat buildup and preserves brake effectiveness for when you actually need to stop.
Shift to a lower gear before beginning descents rather than partway down when brakes are already hot. For steep grades, 3rd or 4th gear provides adequate engine braking while preventing excessive engine RPM. The goal is maintaining 20-30 mph using engine braking supplemented by occasional gentle brake application rather than constant heavy braking.
Turn technique on slippery surfaces requires slowing before turns rather than braking during them. Brake in a straight line before the turn, reducing to appropriate speed. Then navigate the turn with gentle, steady steering and neutral throttle. Avoid braking or accelerating mid-turn, as this can break traction and cause slides.
Dealing with loss of control requires counterintuitive reactions. If your Subaru begins sliding, reduce throttle pressure (don't brake), steer toward where you want to go (not where you're currently sliding), and avoid sudden inputs that can worsen the situation. Modern vehicles with stability control will often intervene automatically, so let the systems work rather than fighting them.
Pre-Trip Inspection Checklist
The morning before departing for mountain travel, perform these final checks personally:
Tire pressure verification including spare tire. Cold temperatures cause pressure to drop, and proper inflation is critical for traction. Check pressure when tires are cold using a quality digital gauge, inflating to the specification on your door jamb sticker.
Fluid level check for engine oil, coolant, brake fluid, and windshield washer fluid. Top off any that are low. Fill washer fluid reservoir completely—mountain driving uses substantial fluid for clearing salt spray and road grime.
Emergency equipment verification that chains, shovel, flashlight, emergency supplies, and jumper cables or jump starter are present and accessible. Verify flashlight batteries are fresh.
Weather and road condition check using Caltrans QuickMap for highway conditions, mountain resort websites for current conditions at your destination, and NOAA weather forecasts for detailed mountain weather. Verify that chain controls aren't in effect (or that you have chains if they are).
Fuel tank fill to completely full. Mountain driving consumes more fuel than freeway cruising, and gas stations in mountain areas are spaced farther apart and charge premium prices. Starting with a full tank from Ontario ensures adequate fuel.
Light function test of all exterior lights. Mountain driving often involves early morning or evening operation in low light conditions. Verify headlights (low and high beam), taillights, brake lights, and turn signals all function correctly.
Cargo loading should keep emergency equipment accessible. Don't bury chains or emergency supplies under luggage and gear. You need quick access if situations develop requiring emergency equipment.
Destination-Specific Preparation Considerations
Different mountain destinations create different demands requiring specific preparation.
Big Bear via Highway 330 involves sustained grades climbing from 1,000 feet to 7,000+ feet over 30 miles. The elevation gain is dramatic and sustained, testing cooling systems, brakes during descent, and requiring extensive use of engine braking. Fill your fuel tank in Ontario or Running Springs before the final climb—gas in Big Bear costs $0.50-1.00 more per gallon than valley prices.
Mountain High via Highway 2 presents similar elevation gain (2,000 feet to 7,000+ feet) with tighter, more technical curves requiring careful speed management. This route sees less traffic than Highway 330 but also has fewer services. Cell phone coverage is spotty along portions of Highway 2, so download offline maps before departure.
Mammoth Mountain via US-395 involves several hundred miles of highway driving before reaching the mountain area. This extended distance means your Subaru must be mechanically perfect for the entire journey—any issues will worsen over 300+ miles. Complete any overdue service before attempting the Mammoth drive, and carry spare fluids (oil, coolant) for emergency top-offs.
Interstate 15 over Cajon Pass to Las Vegas or mountain areas beyond involves high-speed highway driving followed by sustained grades. This route is heavily traveled and well-maintained, but winter storms can close it entirely or implement chain controls with little warning. Check Caltrans QuickMap immediately before departure and have flexibility to postpone travel if severe weather is forecast.
Schedule Your Winter Preparation Service Today
Southern California's proximity to genuine winter conditions creates a unique situation: you live in a mild climate but can reach severe winter conditions in 90 minutes. This accessibility means winter preparation isn't optional for Subaru owners who enjoy mountain activities—it's essential for safety and legal compliance.
Your Subaru's Symmetrical All-Wheel Drive provides exceptional capability when combined with proper winter tires, comprehensive vehicle preparation, and appropriate driving techniques. The legendary "go-anywhere" reputation Subaru has earned comes from this combination of engineering and preparation working together.
Our certified Subaru technicians understand exactly what mountain winter driving demands from your vehicle. We perform comprehensive winter preparation services including battery testing, coolant system inspection, brake evaluation, and all systems critical for reliable mountain operation. We can install winter tires, provide emergency equipment packages, and ensure your Subaru is ready for whatever mountain conditions you'll encounter.
Schedule your winter preparation service today by calling our service department or booking online. We're located at 1195 Auto Center Drive in Ontario, easily accessible from I-10, I-15, and Haven Avenue. Don't wait until chain control turns you around or until you're struggling with inadequate traction to discover your Subaru wasn't ready for mountain winter conditions. Prepare now and enjoy the confidence that proper winterization provides.
Proper winter preparation ensures safety, prevents breakdowns, provides legal compliance with chain requirements, and allows you to enjoy Southern California's incredible mountain winter recreation with confidence. That's the capability Subaru engineered into your vehicle. ⛰️❄️🚙