By Clearwater Oil · Reviewed October 15, 2026 · Steve & Eugenia Pittman, independent AMSOIL Dealer #30575602. Our AMSOIL shopping links include our dealer number; purchases are handled by AMSOIL.
Twenty minutes, two thousand feet.
Lewiston sits at about 745 feet, and Idaho’s lowest point is where the Clearwater meets the Snake. Head north on U.S. 95 and the Lewiston Hill climbs roughly 2,000 feet to the Palouse. Head south or east and you reach the Camas Prairie, where the towns sit far higher than the Valley.
| Place | Elevation | Average January low | Record low |
|---|---|---|---|
| Lewiston (airport) | 745 ft | 30.3°F | −22°F |
| Moscow | 2,582 ft | 22.2°F | −26°F |
| Grangeville | 3,399 ft | 24.5°F | −24°F |
| Cottonwood / Craigmont | 3,521 / 3,747 ft | Prairie towns higher than Grangeville; check the forecast for where the vehicle will park. | |
A typical January night is about 6–8°F colder in Moscow and Grangeville than in Lewiston, and every one of these places has seen well below zero. A truck fueled in the Valley and parked overnight on the Prairie is meeting the Prairie’s temperatures.
Elevations are each city’s published elevation; the Lewiston Hill climb is approximate. Temperatures are NOAA 1991–2020 climate normals for the Lewiston–Nez Perce County Airport, University of Idaho (Moscow), and Grangeville stations; record lows cover each station’s full history. NOAA U.S. Climate Normals.
Three numbers worth knowing.
- Cloud point: the temperature where wax crystals first appear as diesel cools. Below it, those crystals can begin plugging filters. It is the most commonly used cold-weather fuel measure.
- Cold filter plugging point (CFPP): the temperature at which a set amount of fuel can no longer be drawn through a test filter in a set time.
- Pour point: the temperature where the fuel holds so many crystals it is essentially a gel and stops flowing.
Cold-flow additives usually do not change cloud point, but they can lower CFPP. Suppliers also blend No. 1 diesel into No. 2 for winter, and the right blend depends on where and when the fuel is used. There is no single diesel cold-weather specification that covers every ambient condition, so cold-weather performance is something to confirm with your fuel supplier.
Definitions and blending: NREL Biodiesel Handling and Use Guide, 6th ed. (U.S. Department of Energy, PDF) and Cenex: cold-weather diesel problems.
A winter diesel plan for Valley drivers.
1. Know where the vehicle will sit overnight.
Plan around the coldest place the vehicle or equipment will be parked, including a job site, a farm shop, a trailhead, or a relative’s driveway on the Prairie. Check Idaho 511 and WSDOT’s travel map before a winter trip up the grade.
2. Ask about the fuel you are buying.
Ask your station or fuel supplier whether its diesel is a winter blend and what cloud point or CFPP it is blended for. That matters most for bulk or farm tanks filled earlier in the season, before winter blends arrived.
3. Treat before the cold, not after.
AMSOIL Diesel Cold Flow (ADD) is preventive. AMSOIL directs adding it before filling the tank while the fuel is still above its cloud point. It does not reverse gel or wax crystals that have already formed, and crystals that form before treatment remain. Measure the dose from the current label for the fuel quantity.
4. Keep up with filters and water.
Change fuel filters on the equipment maker’s schedule and drain water separators as directed. Water in fuel can freeze and adds to cold-weather filter trouble. For stored fuel and farm tanks, see our on-farm fuel storage notes.
5. Confirm oil and coolant for the season.
Check your owner’s manual for the oil viscosity grades permitted at the temperatures you expect. Some diesel engines allow a lower first number (for example, 5W-40 or 10W-30 instead of 15W-40) for cold starts. Test coolant freeze protection and use the engine heater or cold-weather equipment your manufacturer specifies.
Diesel with up to 5% biodiesel generally performs about like No. 2 diesel in cold weather. Higher blends can need more cold-weather planning, so ask your supplier what you are buying.
If the fuel has already gelled.
A cold-flow additive will not fix gelled fuel. AMSOIL Diesel Recovery (DRC) is made for that situation: it dissolves gelled diesel and thaws frozen fuel filters. Its directions include steps for the fuel filter as well as the tank, so do not assume a tank-only dose will restore operation. Follow the label and the equipment maker’s instructions, get the vehicle somewhere warmer if you safely can, and once it is running again, treat the remaining fuel to prevent another gel.
Keep a spare fuel filter and a bottle of Diesel Recovery in the truck through winter if you regularly drive or park above the Valley.
Choose the AMSOIL product for the job.
Compare these against your owner’s manual and the product label. Open each product page for current directions, sizes, price, and availability. Every shopping link includes Clearwater Oil dealer number 30575602.
| Job | Product at AMSOIL | Check before buying |
|---|---|---|
| Prevent gelling | Diesel Cold Flow · ADD ↗ | Add before filling, above the fuel’s cloud point. Preventive only. |
| All-in-one winter treatment | Diesel 4-in-1 · ADB ↗ | Combines injector cleaning, lubricity, cetane, and cold-flow functions. Use the label’s temperature-specific dose. |
| Fuel has gelled | Diesel Recovery · DRC ↗ | Emergency treatment; follow the filter and tank steps in its directions. |
| Check stored fuel | Diesel Fuel Contamination Test ↗ | Lab test for water, sediment, and aerobic bacteria. It does not measure cloud point. |
| Engine oil | Max-Duty Diesel 5W-40 · DEO ↗ Max-Duty Diesel 15W-40 · DME ↗ | Use a viscosity and specification your engine’s manual allows for the expected temperatures. |
| Coolant | Heavy-Duty Antifreeze & Coolant · ANTHD ↗ | Match the engine’s coolant specification; follow the label rather than mixing by color. |
Browse Clearwater Oil’s fuel additive catalog · Diesel oils · Fall and winter maintenance guide
YOUR CLEARWATER OIL CONNECTION
Tell Steve where your diesel spends the winter.
Share the engine, the fuel you buy or store, where the vehicle parks overnight, and how it is used: commuting up the grade, towing, farm work, or sitting until spring. Steve can help you compare AMSOIL products and treatment rates for your plan.
This original Clearwater Oil planning guide draws on the U.S. Department of Energy, NOAA, fuel-supplier, and AMSOIL references linked alongside the relevant sections. It is not an AMSOIL publication or a substitute for your vehicle or equipment manual.