Doc's Diesel 5W-40 bottle front view highlighting heavy-duty protection.
Doc's Diesel 5W-40 bottle back showing API CJ-4/CK-4 compatibility.
Doc's Diesel 5W-40 label close-up with synthetic oil quality cues.
Doc's Diesel 5W-40 in an engine bay for all-weather protection.
Pouring Doc's Diesel 5W-40 into a heavy-duty engine during service.
Doc's Diesel 5W-40 bottle on a workshop bench signaling durability.
Color-coded packaging details of Doc's Diesel 5W-40 for quick identification.
Doc's Diesel 5W-40 on a vehicle engine bay for dependable performance.
Doc's Diesel 5W-40 bottle front view highlighting heavy-duty protection.
Doc's Diesel 5W-40 bottle back showing API CJ-4/CK-4 compatibility.
Doc's Diesel 5W-40 label close-up with synthetic oil quality cues.
Doc's Diesel 5W-40 in an engine bay for all-weather protection.
Pouring Doc's Diesel 5W-40 into a heavy-duty engine during service.
Doc's Diesel 5W-40 bottle on a workshop bench signaling durability.
Color-coded packaging details of Doc's Diesel 5W-40 for quick identification.
Doc's Diesel 5W-40 on a vehicle engine bay for dependable performance.

Doc's Diesel 5W-40 Full Synthetic Heavy Duty Diesel Oil DOCS5W40-3 | 3-Gallons

Engineered for modern diesel engines Doc's Diesel 5W-40 Full Synthetic Heavy Duty Diesel Oil is designed to...
Vendor: Doc's Auto Parts
Availability: In stock
£183.20
£183.20
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Doc's Diesel 5W-40 bottle front view highlighting heavy-duty protection.

Doc's Diesel 5W-40 Full Synthetic Heavy Duty Diesel Oil DOCS5W40-3 | 3-Gallons

£183.20
Doc's Diesel 5W-40 bottle front view highlighting heavy-duty protection.
Doc's Diesel 5W-40 bottle back showing API CJ-4/CK-4 compatibility.
Doc's Diesel 5W-40 label close-up with synthetic oil quality cues.
Doc's Diesel 5W-40 in an engine bay for all-weather protection.
Pouring Doc's Diesel 5W-40 into a heavy-duty engine during service.
Doc's Diesel 5W-40 bottle on a workshop bench signaling durability.
Color-coded packaging details of Doc's Diesel 5W-40 for quick identification.
Doc's Diesel 5W-40 on a vehicle engine bay for dependable performance.

Doc's Diesel 5W-40 Full Synthetic Heavy Duty Diesel Oil DOCS5W40-3 | 3-Gallons

£183.20
Description
Description
x

Engineered for modern diesel engines

Doc's Diesel 5W-40 Full Synthetic Heavy Duty Diesel Oil is designed to perform in severe conditions with premium synthetic base oils and CK-4 additives. It works well in both new emissions-compliant rigs and older engines, helping resist oxidation, maintain consistent viscosity, and support long-lasting durability under heavy use.

Key benefits for your engine

  • Excellent wear protection under high-load operation, reducing metal wear during demanding drives.
  • Strong oxidation and thermal stability to minimize deposits in tough environments.
  • Stay-in-grade viscosity under heat and shear, helping maintain protection during peak workloads.
  • Fast cold-start protection across all seasons, aiding smoother starts in low temperatures.
  • All-weather performance suitable for on- and off-highway use, including severe service, towing, or dusty conditions.

Performance, compatibility, and fuel considerations

The oil is formulated to meet or exceed major specs, including API CJ-4/CK-4, and carry broad OEM compatibility. It supports 2017 GHG-compliant diesel engines and is designed to help balance emissions considerations with dependable lubrication and potential fuel-economy benefits under varied operating loads.

Specifications and service guidance

  • Meets or exceeds API CJ-4/CK-4; backward compatibility with earlier CJ-4 family specifications and multiple OEM approvals.
  • Replacement guidelines: For standard service, consider 10,000–15,000 miles; for severe service, 7,500–10,000 miles; for off-road or equipment use, follow manufacturer guidelines (hours may apply).

Doc’s brand ecosystem

Doc’s Diesel oil accompanies a robust lineup of filters and maintenance parts designed to meet or exceed OEM standards. This cohesive approach supports reliable performance and ease of maintenance for fleet or individual use, backed by a Northwest Ohio-based team committed to value and service.

FAQ

Q: What engines is Doc's Diesel 5W-40 suitable for?

A: Suitable for modern diesel engines with emissions systems and older engines; meets API CJ-4/CK-4 and supports multiple OEM specs.

Q: How often should I change the oil with Doc's Diesel 5W-40?

A: Follow the vehicle maker’s recommended intervals; severe service may shorten the span (roughly 7,500–10,000 miles), normal service up to 15,000 miles.

Shipping & Return
Shipping & Return
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Returns Policy

You may return most new, unopened items within 30 days of delivery for a full refund. We'll also pay the return shipping costs if the return is a result of our error (you received an incorrect or defective item, etc.).

You should expect to receive your refund within four weeks of giving your package to the return shipper, however, in many cases you will receive a refund more quickly. This time period includes the transit time for us to receive your return from the shipper (5 to 10 business days), the time it takes us to process your return once we receive it (3 to 5 business days), and the time it takes your bank to process our refund request (5 to 10 business days).

If you need to return an item, simply login to your account, view the order using the "Complete Orders" link under the My Account menu and click the Return Item(s) button. We'll notify you via e-mail of your refund once we've received and processed the returned item.

Shipping

We can ship to virtually any address in the world. Note that there are restrictions on some products, and some products cannot be shipped to international destinations.

When you place an order, we will estimate shipping and delivery dates for you based on the availability of your items and the shipping options you choose. Depending on the shipping provider you choose, shipping date estimates may appear on the shipping quotes page.

Please also note that the shipping rates for many items we sell are weight-based. The weight of any such item can be found on its detail page. To reflect the policies of the shipping companies we use, all weights will be rounded up to the next full pound.

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