Will Insurance Cover DEF in a Diesel Tank?

Diesel exhaust fluid (DEF) accidentally added to a diesel fuel tank can cause major engine damage. Unfortunately, most car insurance policies won’t cover the costly repairs. Here’s what you need to know about DEF contamination claims and tips for avoiding denial.

What is DEF and Why is it Harmful in a Diesel Tank?

DEF is a fluid used in diesel engine exhaust systems to lower emissions. It’s comprised of urea and deionized water.

All modern diesel vehicles have a separate DEF tank that injects fluid into the exhaust to convert harmful NOx gases into nitrogen and water vapor. This secondary tank should never be confused with the main diesel fuel tank.

If DEF is mistakenly added to the diesel tank, it will dilute the fuel and cause serious drivability problems. DEF can also corrode metal fuel system components. Just a few gallons of contamination can ruin an entire fuel system.

Repairs often include:

• Cleaning/replacing the fuel tank
• New fuel lines, filters, pumps
• Injector replacement
• Full diesel flush

Bills frequently exceed $5,000 to $10,000 depending on the extent of damage.

Why Insurance Companies Deny DEF Contamination Claims

Unfortunately, most standard car insurance policies explicitly exclude pollution-related damages. Adding DEF or any other foreign substance to your fuel tank is considered “misfueling” by insurers.

So even if you have comprehensive coverage, which covers non-crash damages, contamination claims are often denied. Insurance providers view it as improper maintenance or negligence on the driver’s part rather than a covered peril.

Some insurers may pay if you can conclusively prove:

• Someone else put DEF in your tank intentionally (vandalism)
• The repair shop made the error

But it’s very difficult to prove liability in most situations since the contamination is self-inflicted accidentally.

Tips for Getting DEF Contamination Covered

While most insurers won’t pay DEF claims, a few exceptions exist. Here are some tips to potentially get your contamination repairs covered:

1. Ask Your Agent Upfront

Don’t assume your policy excludes DEF damages. Some providers will cover it, especially under comprehensive coverage. But guidelines vary between insurance companies and individual agents.

Call your agent and specifically ask if adding DEF to the diesel tank would be covered and subject to the deductible. Get confirmation in writing if possible.

2. Highlight the DEF Tank Misfill

If you do have contamination and need to file a claim, emphasize that the DEF tank was filled incorrectly. Avoid admitting you put DEF in the fuel tank yourself.

Your goal is to show this was an unintentional DEF tank misfill accident, not intentional misfueling. Submit copies of any repair shop receipts also showing DEF was incorrectly added.

3. Claim Vandalism

As a last resort, you may be able to allege vandalism, stating someone unknown added DEF to your diesel tank. Of course, this fraudulent claim could backfire if uncovered. But most insurers cover valid vandalism under comprehensive policies.

4. Fight Claim Denials

Don’t take no for an answer if your DEF claim gets denied. Politely argue why the damage should be covered under your policy’s comprehensive terms. Escalate to a supervisor if needed.

Highlight it was an accidental DEF tank mix-up. Also explain how costly repairs are creating financial hardship. An insurer may reconsider upon appeal.

5. Switch Providers

If your claim gets denied and you’re stuck paying the hefty repair bill, consider changing insurance companies. Find a provider that specifies DEF contamination coverage in their policy language.

USAA, State Farm, and several other major insurers don’t cover DEF misfueling damages based on feedback from policyholders. But smaller regional insurers may offer better pollution damage coverage.

Shopping around also gives you a chance to save money on premiums. Comparing rates from a few top insurers could score you a lower price.

Steps to Avoid Expensive DEF Contamination

Since insurance likely won’t pay for DEF-related repairs, prevention is key. Here are important safeguards:

• Never pour DEF yourself – Only let qualified technicians handle DEF fills and maintenance.
• Avoid DIY repairs – Trying to save money by doing it yourself often backfires.
• Label tanks clearly – Use very obvious stickers/tags to differentiate the tanks.
• Add dye to DEF – Some mechanics add dye so it’s visibly distinct from diesel.
• Supervise fills – Watch any DEF filling to ensure the correct tank is accessed.
• Install misfueling prevention – Some new systems block/alert when wrong filler is used.
• Seal tanks – Locking caps can prevent tampering.
• Keep receipts – Save all fuel and DEF purchase receipts in case you need to prove where contamination occurred.

Taking preventative measures will help avoid accidental DEF tank contamination scenarios down the road. But if you do suffer a mishap, be prepared for a likely insurance claim denial. Only a select few providers cover DEF mix-ups.

The best recourse is trying to prove vandalism, fighting the denial, or switching insurers after-the-fact. And in the future, take steps to avoid misfueling accidents since you’ll likely be stuck with the hefty repair bills.