OIL RESTOCK

Restocked & Ready To Ship

Diesel oil is back in stock, same FR3 Nano Technology formula, same protection, plus Oil Change Kits and Oil + Filter Kits.

Quantities are limited, so shop now, or subscribe to any oil product for 15% off your first order and 5% off every order after (auto-applied at checkout, through August 31).

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4.75 out of 5 · 11,500+ verified reviews
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U.S.-BASED SUPPORTREAL HUMANS. REAL FAST.
SHIPS FROM OHIO U.S.FAST DOMESTIC FULFILLMENT
OEM PERFORMANCEEXCEEDS FACTORY STANDARDS
DOC'S QUALITY PROMISEUS-DESIGNED. US & GLOBALLY MADE.
FREE U.S. SHIPPINGORDERS OVER $99*
FITMENT GUARANTEEDEXACT MATCH ASSURED
30 DAY WARRANTYMONEY BACK GUARANTEE
U.S.-BASED SUPPORTREAL HUMANS. REAL FAST.
SHIPS FROM OHIO U.S.FAST DOMESTIC FULFILLMENT
OEM PERFORMANCEEXCEEDS FACTORY STANDARDS

THE THREE WEIGHTS

5W-40 FULL SYNTHETIC

5W-40 FULL SYNTHETIC

Common for 2019–2024 RAM 6.7L Cummins and many Powerstroke engines. Good cold-weather performance.
Shop 5W-40
15W-40 FULL SYNTHETIC

15W-40 FULL SYNTHETIC

Widely used for older Cummins (2013–2018) and Duramax applications.
Shop 15W-40
10W-30 FULL SYNTHETIC

10W-30 FULL SYNTHETIC

Specified for some newer Cummins engines (2019–2026). Check your owner's manual.
Shop 10W-30

Why Doc's Diesel Oil

01

Full Synthetic, CK-4 Spec

A CK-4 additive package built on synthetic Group III base oils. CK-4 is the current heavy-duty diesel standard — written for engines running DPF, EGR and SCR aftertreatment, and it supersedes CJ-4 for the older trucks.

02

Stays In Grade

CK-4 tightened the requirements on shear stability, oxidation resistance and aeration control over the CJ-4 spec it replaced. Plain version: this oil is still doing its job at the end of the interval, not just the start of it.

03

Runs The Full Interval

10,000–15,000 miles standard service. 7,500–10,000 when you're towing, hauling or running dusty. 250–500 hours off-road. Capacity and interval for your engine are printed right on this page — no guessing in the driveway.

TOP 3 OIL CHANGE KITS

Doc's Diesel Dodge RAM 6.7L/5.9L Cummins 15W-40 Full Synthetic Oil Change Kit 1989-2024 brand_Doc's Diesel Gallons 3

#1 Best Seller — RAM 6.7L/5.9L Cummins 15W-40 Full Synthetic Oil Change Kit (1989–2024)

Our top-selling Oil Change Kit. Doc's Diesel 15W-40 Full Synthetic oil paired with a matched oil filter — grab it and go.
Shop Now
Doc's Diesel Ford 6.7L Powerstroke 5W-40 Full Synthetic Oil Change Kit 2011-2025 brand_Doc's Diesel Gallons 4

Top Seller — Ford 6.7L Powerstroke 5W-40 Full Synthetic Oil Change Kit (2011–2026)

Doc's Diesel 5W-40 Full Synthetic oil and a matched Powerstroke oil filter, bundled for a quick, no-guesswork oil change.
Shop Now
Doc's Diesel Chevrolet/GMC 6.6L Duramax 15W-40 Full Synthetic Oil Change Kit 2001-2019 brand_Doc's Diesel Gallons 3

Chevrolet/GMC 6.6L Duramax 15W-40 Full Synthetic Oil Change Kit (2001–2019)

Doc's Diesel 15W-40 Full Synthetic oil matched to your Duramax's oil filter — everything for the job, in one order.
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TOP 3 OIL + FILTER MAINTENANCE KITS

Doc's Diesel RAM 6.7L Cummins 10W-30 Full Synthetic Oil + Filter Maintenance Kit 2019-2024 brand_Doc's Diesel Gallons 3

#1 Best Seller — RAM 6.7L Cummins 10W-30 Full Synthetic Oil + Filter Maintenance Kit (2019–2024)

Our top-selling Oil + Filter Maintenance Kit. Every filter your Cummins needs, plus Doc's Diesel 10W-30 Full Synthetic oil, in one box.
Shop Now
Doc's Diesel RAM 6.7L Cummins 5W-40 Full Synthetic Oil + Filter Maintenance Kit 2019-2024 brand_Doc's Diesel Gallons 3

Top Seller — RAM 6.7L Cummins 5W-40 Full Synthetic Oil + Filter Maintenance Kit (2019–2024)

The full filter lineup and Doc's Diesel 5W-40 Full Synthetic oil, bundled for a complete, no-hassle service.
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Doc's Diesel RAM 6.7L Cummins 15W-40 Full Synthetic Oil + Filter Maintenance Kit 2013-2018 brand_Doc's Diesel Gallons 4

RAM 6.7L Cummins 15W-40 Full Synthetic Oil + Filter Maintenance Kit (2013–2018)

Everything needed for a full-service maintenance stop on older Cummins trucks — filters plus Doc's Diesel 15W-40 Full Synthetic oil.
Shop Now

Restocked And Ready To Ship

Your maintenance schedule doesn't have to wait any longer.

Shop Oil & Kits

Oil Restock — FAQs

15% off your first subscription order. Valid on any subscription that includes Doc's Diesel oil — oil on its own, Oil Change Kits, or Oil + Filter Maintenance Kits. New subscribers only.

The 15% is the total discount on the first order and replaces the standard 5% subscription discount — it doesn't stack on top of it. Every order after the first is 5% off.

Discount applies automatically at checkout, no code required. Cannot be combined with other offers. Offer ends 11:59pm on August 31, 2026.

Oil weight is engine and model-year specific. As a general guide:

  • 5W-40 — Common for 2019–2024 RAM 6.7L Cummins and many Powerstroke engines. Good cold-weather performance.
  • 10W-30 — Specified for some newer Cummins engines (2019–2026). Check your owner's manual.
  • 15W-40 — Widely used for older Cummins (2013–2018) and Duramax applications.

Always refer to your owner's manual or the Cummins/Ford/GM service spec for your exact engine year. Doc's Diesel maintenance kits bundle the correct oil and filters together — no guesswork required.

Note: Not sure which kit is right? Email sales@docsdiesel.com with your year, make, engine, and we'll point you in the right direction.

We've made a modest price adjustment on select oil products due to rising raw material costs — our formula and quality haven't changed. Read the full pricing update →

Oil Change Kits pair Doc's Diesel full synthetic oil with a matched oil filter — everything for a straightforward oil change.

Oil + Filter Maintenance Kits go further, bundling the full filter service — fuel/water separator, fuel filter, oil filter, air filter, and cabin filter — plus the correct oil, in one box.

REAL TRUCKS. REAL OIL CHANGES.

★★★★★

“I use the filters and oil kits to service my fleet of trucks (4). I own a landscaping company and we are hard on our trucks, and it's nice to have a convenient way to buy the correct amount of oil and all filters in one place.”

Kameron C.
Verified Buyer
★★★★★

“I did my oil change with y'all's 10 W 30 full synthetic with the hot shot secret with fuel filters and immediately knew the difference and sounded better. Ran better. I was getting 20 miles to the gallon now I'm upwards of 24. Absolutely getting this for the rest of its life and my next truck's life.”

Brandon H.
Verified Buyer
★★★★★

“Doc's actually has some dang good filters, heck even their sticker pack actually comes with usable stickers that ain't so small nobody notices them. Ordered fuel filters for my 2016 6.7 Cummins and Doc's sent updates for every step of the way, and they shipped to my house within 3 days. Cheaper than the parts store, noticeable quality, and shipped out the same day I ordered em. So overall nothing bad to say and will definitely be upgrading my fleet to all docs filters.”

TB Cattle Co
Verified Buyer
★★★★★

“Easy to order, had a question got a call back very quickly and product was very nice stuff! Definitely will continue ordering my oil changes through docs 👍”

Dakota W.
Verified Buyer
★★★★★

“I use the filters and oil kits to service my fleet of trucks (4). I own a landscaping company and we are hard on our trucks, and it's nice to have a convenient way to buy the correct amount of oil and all filters in one place.”

Kameron C.
Verified Buyer
★★★★★

“Doc's actually has some dang good filters, heck even their sticker pack actually comes with usable stickers that ain't so small nobody notices them. Ordered fuel filters for my 2016 6.7 Cummins and Doc's sent updates for every step of the way, and they shipped to my house within 3 days. Cheaper than the parts store, noticeable quality, and shipped out the same day I ordered em. So overall nothing bad to say and will definitely be upgrading my fleet to all docs filters.”

TB Cattle Co
Verified Buyer
★★★★★

“I did my oil change with y'all's 10 W 30 full synthetic with the hot shot secret with fuel filters and immediately knew the difference and sounded better. Ran better. I was getting 20 miles to the gallon now I'm upwards of 24. Absolutely getting this for the rest of its life and my next truck's life.”

Brandon H.
Verified Buyer
★★★★★

“Easy to order, had a question got a call back very quickly and product was very nice stuff! Definitely will continue ordering my oil changes through docs 👍”

Dakota W.
Verified Buyer
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