SAE Viscosity Table
| Winter grade | Max cranking viscosity (CCS) | Max pumping viscosity (MRV) | Min viscosity at 100 C (cSt) |
|---|---|---|---|
| 0W | 6,200 at -35 C | 60,000 at -40 C | 3.8 |
| 5W | 6,600 at -30 C | 60,000 at -35 C | 3.8 |
| 10W | 7,000 at -25 C | 60,000 at -30 C | 4.1 |
| 15W | 7,000 at -20 C | 60,000 at -25 C | 5.6 |
| 20W | 9,500 at -15 C | 60,000 at -20 C | 5.6 |
| 25W | 13,000 at -10 C | 60,000 at -15 C | 9.3 |
Hot grades (kinematic band at 100 C, HTHS at 150 C)
| Grade | Min cSt at 100 C | Max cSt at 100 C | HTHS (cP) |
|---|---|---|---|
| 8 | 4.0 | under 6.1 | 1.7 |
| 12 | 5.0 | under 7.1 | 2.0 |
| 16 | 6.1 | under 8.2 | 2.3 |
| 20 | 6.9 | under 9.3 | 2.6 |
| 30 | 9.3 | under 12.5 | 2.9 |
| 40 | 12.5 | under 16.3 | 3.5 |
| 50 | 16.3 | under 21.9 | 3.7 |
| 60 | 21.9 | under 26.1 | 3.7 |
The W in 5W-30 stands for winter, and the first number is a cold-weather test, not a thickness: W grades are certified by how well the oil cranks an engine and keeps pumping at hard freezes, measured in the table in centipoise at temperatures from -10 down to -40 degrees C. A 0W certifies cranking viscosity below 6,200 cP at -35 C; a 25W gets by with up to 13,000 cP but only down to -10 C. The pumping column matters just as much - an oil can pour fine and still fail the pump at startup, which is why 60,000 cP limits appear on every winter grade, each at its own temperature.
The second number is a different oil at a different day: it certifies the kinematic viscosity band at 100 degrees C (operating temperature, roughly 9.3 to 12.5 cSt for a 30) plus a high-shear floor called HTHS - the viscosity the oil film holds between hot, fast-moving parts. So 5W-30 is two separate certificates stapled together: winter behavior from the 5W row of the first table and hot behavior from the 30 row of the second. Neither number says anything about quality or durability - they are a cold envelope and a hot envelope, and the engine manual picks the pair.
How to use
- Match the manual, then the climate: the manual lists the grade pair and usually a colder alternative - if winters drop past the cranking temperature of your current W grade, step down the winter number (10W to 5W to 0W) without touching the hot number.
- Read the winter rows by temperature first: find the coldest your region realistically parks in, then pick the W grade whose test temperature covers it - a 5W is certified to -30 C cranking, a 0W to -35 C.
- Never trade the hot grade for the cold one: the second number is the oil film at operating temperature, and engines are built around its band - thinner saves a whisper of fuel on paper and can take the bearings out of spec where it counts.
Frequently asked questions
What is the difference between 5W-30 and 10W-30?
Only the cold test. Both share the 30 hot grade - identical kinematic band of 9.3 to 12.5 cSt at 100 degrees C and the same HTHS floor - so once the engine is warm, the two oils behave the same. The difference is the winter row: 5W must crank below 6,600 cP at -30 C and pump below 60,000 cP at -35 C, while 10W gets a warmer window of -25 and -30 C respectively. Practically: in climates that rarely park below -20 C, both grades cover the morning start, and the manual's preference wins; in real cold, the 5W (or 0W) is the difference between the crank spinning and the battery dying at -30. This is why cross-grade shopping is about the W number only - the second number is not a strength dial.
Can I use 0W-20 where the manual says 5W-20?
Almost always yes, and the table explains why: 0W is a strictly harder cold test than 5W (cranking under 6,200 cP at -35 C versus 6,600 cP at -30 C), so an oil certified 0W already exceeds the 5W winter requirement. The hot grade matches, so the engine sees the same film at operating temperature. The caveats live at the edges: some engines with variable-valve-timing or oil-pressure systems were calibrated with an expected viscosity band in mind, so the manual's fine print - not the table - is the final word on going thinner than the specified hot grade, and 0W-20 versus 5W-30 type swaps (both numbers changed) are a different question entirely. Going more winter than the manual asks is the safe direction on paper; going less winter or different hot is where warranties and wear live.
What does HTHS viscosity actually protect?
It is the oil film number under the worst second of engine life: high temperature, high shear - the microscopic gap between a journal bearing and its shaft at full load, where the oil is squeezed, churned and 150 degrees hot. The J300 rows put a floor under it (2.9 cP for a 30, 3.5 for a 40) because that film is what keeps metal from kissing metal; an oil can pass every other test and still fail here if its polymer thickeners shear down in service. This is also the quiet story behind the 40 versus 30 choice in Europe versus America: tighter bearing clearances and different duty cycles pushed European specs toward higher HTHS floors, which is why the same engine family can spec 5W-30 in one market and 5W-40 in another without either being wrong.
Why are the winter grades measured at different temperatures?
Because the grade is defined by the challenge it survives, not by a single cold point: a 25W is a cold-morning oil for climates that rarely see -10 C, so it is tested at -10 C cranking; a 0W promises the Arctic, tested at -35 C cranking and -40 C pumping. Each row of the winter table is the same two questions asked at that grade's own frontier - can the starter still spin the crank (cranking viscosity, CCS) and can the pump still lift oil a few seconds later (pumping viscosity, MRV, the 60,000 cP line). The pumping test is the sneakier failure: oil can be thin enough to crank and still slump like cold honey at the pickup tube, starving the engine right after it fires - which is why every winter row pairs the two numbers instead of trusting one.