Frequently Asked Questions

Yes! Doc's Diesel has expanded its product line to cover gas cars, trucks, and SUVs — all on the same website. You'll find gas-specific engine air filters, cabin air filters, oil filters, fuel filters, performance engine air filters (MaxFlow), wiper blades, and additives.

Same no-BS guarantee and fitment assurance. Built for whatever's in your driveway. Shop gas products →

You can email us directly at sales@docsdiesel.com or submit a form through our Contact Us page.

Doc's Diesel is located at 701 Brunicardi Way, Bryan OH 43506. You can reach us by phone at (419) 551-6138 or by email at sales@docsdiesel.com.

Doc's Diesel filters meet or exceed Original Equipment Manufacturer (OEM) specifications. When installed correctly and per the engine manufacturer's recommended service intervals, using Doc's Diesel parts will not void your new vehicle warranty. See our official Limited Warranty for full details, or read our Aftermarket vs. OEM Parts: What's the Difference? blog for a full breakdown.

Yes — Doc's Diesel filters are available on Amazon, eBay, and Walmart. It's the exact same product, and same great quality. Shop wherever is most convenient for you.

Absolutely. Submit a product request through our Product Recommendation Form — it takes less than 2 minutes and no account is required. We review every submission, and if a product gets enough requests it moves up our sourcing list. You'll be notified by email if and when it's added.

At Doc's Diesel, we're committed to delivering premium-quality oils and fluids that protect your truck for the long haul.

Like many manufacturers, we've seen increases in the cost of raw materials. We've worked to absorb these costs for as long as possible, but to maintain the quality and performance you expect, we've made a modest price adjustment on select oil and transmission fluid products.

What's Changing?

Effective July 9, 2026:

• Engine oil gallon jugs: $4 increase per gallon
• Transmission fluid gallon jugs: $3 increase per gallon
• Oil and transmission service kits have been adjusted accordingly.

What Isn't Changing?

Our commitment to quality.

We're not changing our formulas, cutting corners, or lowering our standards. Every bottle is still made with premium ingredients and engineered to deliver the protection and performance your truck deserves.

Thank You

We know price increases are never welcome, and we don't make these decisions lightly. Our goal is to continue providing the quality, performance, and value you've come to expect from Doc's Diesel.

Thank you for choosing Doc's Diesel and for trusting us to help keep your truck running its best. If you have any questions about this pricing update or any of our products, our Customer Service team is always happy to help.

Yes. We don't just claim OEM-matching quality — we prove it. Doc's Diesel filters undergo third-party testing to verify filtration efficiency and flow rate. You can review the actual test results on our Understanding Filtration page.

Doc's Diesel carries parts for all of the major diesel truck and SUV platforms:

• Cummins: RAM 6.7L (2007.5–2026), RAM 5.9L (1989–2007 12V/24V), Nissan Titan XD 5.0L (2016–2019)
• Powerstroke: Ford Super Duty 7.3L (1994–2003), 6.0L (2003–2007), 6.4L (2008–2010), 6.7L (2011–2026); Ford F-150 3.0L (2018–2025)
• Duramax: Chevy Silverado HD / GMC Sierra HD — all L5P, LML, LBZ, LLY, LB7 generations; Silverado 1500/Sierra 1500 3.0L (2020–2025); Colorado/Canyon 2.8L (2016–2022)
• EcoDiesel: RAM 1500 3.0L (2014–2025), Jeep Wrangler/Gladiator 3.0L (2020–2025), Jeep Grand Cherokee 3.0L (2014–2019)
• Volkswagen TDI: 1.9L/2.0L Jetta, Golf, and others (2005.5–2014)

For diesel trucks our product line includes:

• Fuel filters and fuel/water separators
• Oil filters and full synthetic heavy-duty diesel oil (5W-40, 10W-30, 15W-40)
• Engine air filters
• Cabin air filters
• CCV (crankcase ventilation) filters
• Complete filter kits and oil + filter maintenance kits
• Transmission filters
• Hub assemblies
• Performance brake kits (drilled & slotted rotors + ceramic pads)
• Diesel additives — DPF & injector flush, 24/7 cetane boost treatment, interval treatment

A CCV (Crankcase Ventilation) filter captures oil blow-by vapors before they can re-enter the intake. Over time, a failing or missing CCV filter allows oil mist to coat the intercooler, intake, and turbo — reducing efficiency and causing buildup. Most modern diesel trucks have them stock; replacing the filter on schedule keeps blow-by at bay.

Doc's Diesel carries CCV filters for Cummins and Powerstroke applications. Browse CCV filters →

Doc's Diesel offers three diesel fuel additives, each with a specific purpose:

• Interval Diesel Treatment — Add every 5,000 miles. Cleans injectors, DPFs, and turbos. Treats up to 40 gallons per bottle.
• 24/7 Diesel Treatment + Cetane Boost — Add every fill-up. Boosts cetane up to 7 points, targets water, lubricates fuel pumps and injectors.
• DPF & Injector Diesel Fuel Flush — Use when you want a deep clean. Reduces soot buildup and supports smoother regen cycles.

Browse all additives →

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. Shop maintenance kits →

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.

Doc's Diesel gas product line covers a wide range of makes including Ford, Chevrolet, GMC, RAM, Dodge, Jeep, Cadillac, Nissan, Lincoln, Isuzu, Freightliner, Toyota, Chrysler, Hummer, Infiniti, Lexus, Volkswagen, Porsche, Honda, Mercedes, and Land Rover.

Coverage is growing — use the Shop by Vehicle menu to see what's available for your specific vehicle, or request a part if you don't see yours listed.

The gas product line includes:

• Engine air filters (standard and performance MaxFlow)
• Cabin air filters
• Oil filters
• Fuel filters
• Gas system treatment additive
• Complete gas filter kits
• All-season beam wiper blades

Browse the full gas product line →

MaxFlow is Doc's Diesel's performance engine air filter line for gas vehicles. Designed to improve airflow over a standard OEM paper filter while maintaining solid filtration. A direct drop-in upgrade — no modifications needed. Shop MaxFlow →

Each product listing includes the OEM/dealer part numbers it replaces. For example, a Cummins fuel filter kit will list the corresponding Mopar/Fleetguard numbers. This makes it easy to confirm you're getting the right part before purchasing.

No. Under the Magnuson-Moss Warranty Act, vehicle manufacturers cannot void your warranty simply because you used aftermarket parts — as long as the parts meet or exceed OEM specs and were installed correctly. Doc's Diesel filters meet or exceed OEM requirements and are covered by our official limited warranty.

Note: Always service your vehicle at the manufacturer's recommended intervals to keep your factory warranty intact, regardless of which brand of filters you use.

Yes, for several platforms. The Cummins 5.9L 12V line covers 1989–1998 trucks, and the 24V covers 1998.5–2007. The 7.3L Powerstroke covers 1994–2003. Check the Shop by Vehicle section for your specific year. If coverage doesn't exist yet, submit a product request and we'll review it.

Most manufacturers recommend every 15,000–30,000 miles, but if you drive in dusty, off-road, or construction environments, replace it more frequently. A clogged air filter reduces power, hurts fuel economy, and can accelerate engine wear. Inspect it when you do any other service and replace if it looks gray or dirty.

Typically every 12,000–15,000 miles or once per year — whichever comes first. Signs it's time: reduced HVAC airflow, dusty or musty cabin smell, or increased allergy symptoms while driving. It's an often-overlooked service item that makes a noticeable comfort difference.

Complete Filter Kits bundle all the filters your truck needs for a full service interval — typically fuel filter(s), oil filter, engine air filter, and cabin air filter.

Oil + Filter Maintenance Kits go further by also including the correct quantity and viscosity of Doc's Diesel full synthetic oil, so you have everything you need for an oil change in one box. No separate oil purchase needed.

Shop maintenance kits →

Yes. Doc's Diesel drilled and slotted rotors are designed as direct drop-in replacements for OEM rotors — no caliper modifications required. The ceramic brake pads are also designed to match OEM dimensions for your specific application. Each kit listing specifies the exact vehicle fitment.

Shop performance brake kits →

We ship to the U.S. and Canada. Orders are processed within 1–2 business days (often same-day for weekday orders). Estimated delivery:

• Contiguous U.S.: 3–5 business days from shipment
• Canada: 7–11 business days. Any applicable taxes, duties, or customs fees are the buyer's responsibility.

Check your spam folder first — confirmation and shipment emails sometimes end up there. If you received a confirmation email but not a shipment email, your order is still being processed. Once shipped, tracking info will be in your shipment email.

If you need a status update, email sales@docsdiesel.com with your order number (starts with DD) and we'll check on it right away.

Email sales@docsdiesel.com within 2 hours of placing your order with your order number (starts with DD). We process orders quickly, so the sooner you reach out the better.

Note: Orders placed after 12 PM EST on Fridays are processed Monday morning. If you order over the weekend and need to cancel, email us — we'll handle it first thing Monday.

We accept Amex, Apple Pay, Discover, Google Pay, Mastercard, PayPal, Shop Pay, Venmo and Visa.

Bulk/Fleet orders are not possible through our core website. However, if you did have a fleet of vehicles, we recommend reviewing our Dealer/Wholesale application as that may be an option!

Should there be an item on our website that says we are out of stock, feel free to click “Notify me when available” and you will be alerted when we have replenished our stock.

Please reach out to sales@docsdiesel.com if you need to provide any feedback, you can also leave a review for a product directly on our website!

There are times when the courier may incorrectly scan an item as delivered, so we recommend waiting an additional business day for delivery. However if you require any immediate assistance, please reach out to sales@docsdiesel.com.

Please reach out to sales@docsdiesel.com as soon as possible and our team will help to resolve the issue.

We process orders in 1–2 business days (often less than 24 hours if ordered on a weekday). Depending on location, U.S. orders will arrive within 3–5 business days from when your order was placed.

All UPS Next Day Air and 2-Day Air Shipping orders must be placed before 2 PM EST to ship same day. For example, if you place your 2-Day Air order before 2 PM EST on Wednesday, it will ship that day and arrive Friday. If you place your Next Day Air order after 2 PM EST on Thursday, it will ship Friday and arrive Monday.

Canada orders typically arrive within 7–11 days.

If you haven't received your order confirmation, email us at sales@docsdiesel.com so we can get everything sorted out ASAP.

If you received an order confirmation but no shipment email, we're still working on your order — email us any time for an update.

Tracking information is included in your shipment email. Once a shipment leaves our warehouse, we're at the mercy of the shipping carrier like anyone else, but if there's an issue with your shipment we'll work with you to sort it out. Just email sales@docsdiesel.com with your order number.

Package protection covers your order against carrier damage or loss — approximately $1 per $100 of order value. Cost breakdown by order total:

• Up to $200 — $1.95
• $201–$300 — $2.95
• $301–$400 — $3.95
• $401–$500 — $4.95
• $501–$600 — $5.95
• $601–$700 — $6.95
• $701–$800 — $7.95
• $801–$900 — $8.95
• $901–$1,000 — $9.95

If your order goes missing or arrives damaged, contact us to start a claim. Have your order number ready (starts with DD):

• Phone: (419) 551-6138
• Email: sales@docsdiesel.com

Refunds are issued to the original payment method. Replacements are shipped as soon as the claim is confirmed.

Package protection does not cover the following:

• Theft after delivery — if tracking confirms the package was delivered, file a claim directly with FedEx, USPS, UPS, or local law enforcement.
• Shipping delays — protection only applies when a carrier officially declares a package lost, which typically happens after 15 days of no movement (varies by carrier).
• Incorrect address at checkout — Doc's Diesel is not responsible for orders shipped to an address entered incorrectly. If a package is returned to us, we can resend it at the buyer's expense.

Doc's Diesel products are backed by an official limited warranty covering defects in material and workmanship. Products must meet or exceed OEM specifications and the warranty is valid when parts are installed correctly and in accordance with engine manufacturer recommendations. New vehicle warranties remain in effect when Doc's Diesel parts are used properly.

• View Doc's 3-year/36,000-mile Brake Line Warranty
• View Doc's Hubs Limited Lifetime Warranty

View the Official Limited Warranty document →

Contact us right away at sales@docsdiesel.com or (419) 551-6138 with your order number and a description of the issue (photos help). We'll get it sorted quickly — wrong items and defective products are handled at no cost to you.

• Filters and Brakes: Must be in new and unused condition.
• Oil/Additives: Must be unopened and unused.

1. To start the return process, please visit our Returns Center.
2. Once your return is approved, we'll send you instructions on how to send the item back.
3. Please note that the cost of return shipping is the customer's responsibility.

After we receive your returned items, we'll process your refund—minus the return shipping cost—within 2-4 business days. Refunds will be made to your original method of payment.

• Oversized tires beyond OEM specifications
• Improper installation or failure to torque lug nuts to OEM spec
• Air impact tool installs without a final torque-wrench check
• Off-road, rock crawling, racing, or motorsport use
• Commercial hauling or loads beyond the vehicle's rated GVWR
• Accidents, collisions, or impact damage to the hub
• Hub that has been disassembled, modified, or repacked
• Failure to inspect and replace worn related components at time of installation
• Contamination from water intrusion, mud packing, or chemical exposure
• Neglected maintenance (failure to grease where applicable)
• Purchase by anyone other than the original owner

1. Complete the Warranty Claim Form online, or download and fill out.
2. If you used the fillable PDF, email the completed form and supporting photos to sales@docsdiesel.com. Use subject line: Warranty Claim — [Your Name] — Order [Order #]
3. Our team will review and respond within 3–5 business days.

At Doc's Diesel's sole discretion, approved warranty claims will be resolved by one of the following:

• Replacement with the same or equivalent hub assembly
• Full refund of the original purchase price

Doc's Diesel is not responsible for labor costs, towing, or any incidental or consequential damages.

This warranty is non-transferable and applies only to the original purchaser. Coverage does not transfer upon sale of the vehicle.

You earn Diesel Dollars by:

• Creating an account (25 Diesel Dollars, automatically)
• Referring a friend
• Buying on docsdiesel.com
• Leaving a product review
• Celebrating your birthday
• Following us on Instagram or Facebook

Click here to open the Diesel Diehard pop-up and create your account — it only takes a minute.

Turn your Diesel Dollars into a discount on your next order. We'll email you a code, or you can find it under “Your Rewards” in the Diesel Diehard pop-up.

No — Diesel Diehard coupon codes can't be stacked with other active promotions.

No minimum to redeem your own Diesel Dollars. If you're using a referral code, your friend needs to spend $50+ to get their $10 off.

Log in and add your birthdate to your account. Once your birthday hits (after you've signed up), you'll get 100 Diesel Dollars automatically. They aren't applied retroactively.

Your unique referral link lives in the Diesel Diehard pop-up. Share it — your friend gets $10 off orders over $50, and you get a $10 gift card every time someone orders through your link.

Yes, they're good for about a year. You can see the exact expiration date in the pop-up under your point total.

No. Diesel Dollars only apply to orders placed directly on docsdiesel.com — not third-party sites like Amazon or eBay.

Pick the part you need, choose how often you want it delivered, and we handle the rest. Set it and forget it.

Yes. It renews on its own, so you don't have to think about it.

Log in using the same email you used when ordering, then click “My Subscriptions.” If you have more than one, pick the one you want and select “Manage Subscription” to skip, cancel, reschedule, or update billing and shipping info.

No. You can cancel anytime, free of charge — just do it by 12 PM EST the day before your next order processes. Log in, go to “My Subscriptions,” and select “Cancel Subscription.” Need help? Email sales@docsdiesel.com.

You get 5% off your first order and every order after that. Shipping is calculated separately at checkout.

Log in, go to “My Subscriptions,” select your plan, then choose “Pause” under Frequency. You won't be charged while it's paused. You can also skip just your next order under Subscription Settings.

No — a one-time purchase is always available. But with a subscription you get 5% off every order and never run out of the parts you need.

You're charged when your order is processed and shipped. Log in and check under “Subscription” for your “Next box ships on” date.

Yes. Doc's Diesel offers 11% off for current and former U.S. Military personnel and first responders (including fire, law enforcement, and EMS) through the GOVX verification program. Learn how to access the discount →

Existing wholesale accounts can log in at wholesale.docsdiesel.com. If you're having trouble accessing your account, email sales@docsdiesel.com.