HOW MANY QUARTS OF OIL DOES A SEMI TRUCK TAKE?
Most Class 8 semi trucks take 40–44 quarts (10–11 gallons) of oil with the filter. The exact amount depends on your engine. See the full breakdown by engine below — then find the right oil for the fill.
Semi Truck Oil Capacity by Engine
All figures are fill capacity with a new filter installed. Dry-fill numbers (first startup after rebuild) run higher — always use the dipstick to confirm.
| Engine | Capacity (qt) | Capacity (gal) | Notes |
|---|---|---|---|
| Cummins X15 | 42–44 qt | 10.5–11 gal | Varies by sump config |
| Cummins ISX15 | 42–44 qt | 10.5–11 gal | Same block as X15 |
| Detroit DD15 | 42 qt | 10.5 gal | Standard sump |
| Detroit DD13 | 34 qt | 8.5 gal | Smaller displacement |
| Volvo D13 | 40 qt | 10 gal | VDS-4.5 required |
| Mack MP8 | 40 qt | 10 gal | Shares platform with D13 |
| PACCAR MX-13 | 43 qt | 10.75 gal | Kenworth / Peterbilt |
| PACCAR MX-11 | 34 qt | 8.5 gal | Mid-range option |
| CAT C15 | 42 qt | 10.5 gal | Legacy engine, still common |
| CAT C13 | 34 qt | 8.5 gal | Lighter duty |
| Mercedes OM471 | 42 qt | 10.5 gal | Freightliner Cascadia |
Why the Number Varies Engine to Engine
You’ll see different numbers on different spec sheets for the same engine. Here’s what drives that:
- Sump size: Standard sumps hold less than extended sumps. The Cummins X15 is the clearest example — standard sump is 42 qt, extended is 44 qt. Know which sump you have.
- Dry fill vs. wet fill: A dry fill (fresh engine or post-rebuild) takes more oil because the passages, cooler, and filter are empty. Never pour the dry-fill spec into an engine that already has oil in it.
- Filter volume: A new spin-on filter holds roughly 1 quart. All the numbers in this table already account for the filter. If you’re reusing the old filter (not recommended), your fill will land about 1 qt low.
- Oil cooler fill on first startup: On a fresh engine, the oil cooler circuit needs to fill. The oil level will drop after the first crank — that’s normal. Let it idle, shut it down, wait 5 minutes, check the dipstick again.
Pro tip: Always check the dipstick after filling — never trust the spec alone. Two trucks with identical engines can read differently depending on sump config, cooler priming, or how long since the last drain. The dipstick is the truth.
Overfill warning: Too much oil is as bad as too little in a diesel this size. An overfill can aerate the oil, cause foaming, and blow seals. Stop at the spec, check the stick, and only add small amounts if needed.
How Many Gallons Is That?
If you’re ordering bulk oil or stocking the shop, quarts-to-gallons math matters. Here’s the fast reference:
Quick math: divide quarts by 4 to get gallons. A standard 2.5-gallon jug covers about 10 quarts. For a 42-qt fill you need just over four 2.5-gal jugs — or buy the 5-gallon pails.
What Oil Goes In?
Now you know how much — here’s what. The vast majority of Class 8 diesels run on 15W-40 CK-4 heavy-duty diesel oil. Some newer engines specify 10W-30 for cold-weather or fuel-economy reasons, but 15W-40 covers most fleets year-round in the continental U.S.
15W-40 CK-4
Standard spec for most Class 8 engines. Covers Cummins, Detroit, PACCAR, CAT, and Mercedes OM471. Check your door placard if unsure.
Volvo D13 — VDS-4.5
Volvo’s proprietary spec on top of CK-4. Use an oil that carries VDS-4.5 approval or you risk voiding the warranty and shortening drain intervals.
Mack MP8 — EOS-4.5
Mack’s equivalent to Volvo VDS-4.5. The MP8 and D13 share a platform — both need the Volvo/Mack dual-approved spec.
Synthetic vs. Conventional
Synthetic CK-4 holds up longer between changes and performs better in temperature extremes. Full synthetic is worth it if you’re pushing extended drain intervals.
For a full breakdown by engine: 15W-40 diesel oil specs or best oil for semi trucks.
AMSOIL 15W-40 for Class 8 Diesels
AMSOIL makes two CK-4 15W-40 options built for semi trucks. Both are full synthetic, both carry the heavy-duty approvals your engine needs.
AMSOIL Signature Series Max-Duty 15W-40
The top-shelf option. Built for extended drain intervals — up to 75,000 miles in over-the-road applications. Carries CK-4, API SN, and Volvo VDS-4.5 / Mack EOS-4.5 approvals. If you’re running an X15 or DD15 hard, this is the fill.
- Extended drain intervals (up to 75K miles OTR)
- Volvo VDS-4.5 & Mack EOS-4.5 approved
- Superior soot handling in high-load diesels
- CK-4 / API SN certified
- Full synthetic — holds viscosity longer
AMSOIL Heavy-Duty Synthetic Diesel Oil 15W-40
Solid performer at a lower price point. Full synthetic CK-4, handles standard OEM drain intervals, and meets the specs for most Class 8 engines. Good pick for fleet ops watching cost-per-unit.
- Full synthetic CK-4 formulation
- Meets OEM drain interval specs
- Strong oxidation and deposit control
- Works across Cummins, Detroit, PACCAR, CAT
- Lower cost per quart than Signature Series
Ready to Order?
Pick up AMSOIL 15W-40 in quarts, gallons, or pails at Vyscocity — ships direct, no dealer markup.
Frequently Asked Questions
Most Class 8 semi trucks take between 40 and 44 quarts (10–11 gallons) of engine oil with the filter. The exact capacity depends on the engine. Cummins X15 and ISX15 use 42–44 qt, Detroit DD15 and Mercedes OM471 use 42 qt, PACCAR MX-13 uses 43 qt, Volvo D13 and Mack MP8 use 40 qt, and smaller engines like the DD13, MX-11, and CAT C13 use about 34 qt.
A semi truck holds roughly 10 to 11 gallons of engine oil. The most common Class 8 diesels land around 10.5 gallons (42 qt). Smaller mid-range engines run closer to 8.5 gallons (34 qt). Always verify with your specific engine’s service manual and confirm with the dipstick after filling.
The Cummins X15 (and ISX15) takes 42 to 44 quarts (10.5–11 gallons) of oil with the filter. The range depends on sump configuration — standard vs. extended sump. When in doubt, fill to 42 qt and check the dipstick before adding more. The ISX15 shares the same block and uses identical fill specs.
The Detroit DD15 takes 42 quarts (10.5 gallons) of oil with the filter on a standard sump. This same spec applies to the Mercedes OM471, which shares the same platform in Freightliner Cascadia trucks. The smaller DD13 uses 34 qt (8.5 gal).
All capacity specs listed on this page are with a new filter installed. A new filter holds approximately 1 quart of oil. If you’re doing a drain-and-fill with a new filter, use the full spec (e.g., 42 qt for a DD15). If you’re only topping off without changing the filter, start conservatively and check the dipstick — don’t try to hit the full spec.
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