How Far Can You Drive With DEF Light On? (Helpful Guide)
Driving has become more complicated. In the old days, all you had to worry about was having enough oil, gas, and water in their respective containers. Now with more fluids, like DEF to worry about, you may forget which tank needs filling up at the pump and drive away with the DEF tank nearly empty.
To be honest, not very far. Once the DEF light comes on you may only be able to drive between 50 and 100 miles, depending on your vehicle and the size of the DEF tank. Any further and your vehicle should go into limp mode and that is never any fun.
To learn more about this situation, just continue to read our article. It has the information you want to know about so you can make the right driving decision when your DEF light comes on. Keep in mind that not every gas station in the country has DEF at the pump so be prepared.
Can I Drive With The DEF Light On?
Yes, you can but do not count on going very far. There are many regions of the country that have not upgraded their pump islands and placed a DEF station on them. That means you will not be able to conveniently fill your DEF tank when you fill up with fuel.
When you are driving in these regions, either make sure your tank is full or bring along some jugs of DEF fluid to compensate for this lack of convenience. Being able to drive 50 to 100 miles with the light on is not that far and there is no guarantee you will find a gas station with a DEF pump on the pump island.
If you drive too far, then your vehicle will go into limp mode and when that happens, you won’t be going anywhere very fast. Make sure to keep the DEF tank as full as you can when you are driving through those regions with few DEF at the pump options.
How Far Can You Drive With The Def Light On?
As we said earlier, not very far. When you hit limp mode, you are not going to be driving very safely no matter if you are on the highway or a city street. When the light turns on, it should say something like “5 mph Max Speed in 100 mi, Service DEF System, See Dealer.”
That means that you have 100 miles to get to a dealer before the limp mode activates. When it does you may limp into the dealer or you may have to call a tow truck to get you to one.
Once at the dealer the news may not be good. While most people can simply refill the tank and be on their way, other owners are not so lucky.
An error code may be triggered and if there are damaged parts you may be looking at paying a high repair bill. One DEF pump can cost about $1800 to replace, with most of that money going to labor.
Then replacing a bank 1 NOx sensor can run you $1650 with most of that going to purchase the right part. Be careful with your DEF system as it can really blow a budget even with one part failing.
How Long Will a Quarter Tank Of Def Last?
This will depend on the type of vehicle you own. For example, the average modern truck should get between 7500 to 10,000 miles on a full DEF 9 to 10-gallon tank.
On a medium-sized truck, you are looking at using 2 to 3 gallons of DEF when you drive between 700 to 1200 miles. Your results may vary. For the top figure, it works out to about 75 to 100 miles per gallon.
For the second figure, it works out to about 350 to 600 miles using the lower 2-gallon option. If we used the 3-gallon option then you are looking at getting between 250 and 400 miles per gallon.
As you can see, your results will vary depending on numerous factors. A 1/4 tank will depend on the size of your DEF tank. Some have 2 1/2 gallon capacities, other vehicles have up to 10 gallons.
A 1/4 tank on a 2 1/2-gallon is not very much so do not plan on driving very far with that little amount of DEF.
How Long Can You Go Without DEF?
Again, the best answer that can be given is, not very far. If you try and chance it here are some issues you may cause:
- The exhaust system may be clogged with debris
- Reduces the engine’s overall performance
- Reduces fuel economy
- Increases the harmful emissions
- Limits the speed of the vehicle to 05 mph
- The engine shuts down
When you are driving long distances and you see that DEF warning light come on, either pull into a gas station that has DEF at the pump and make that move quickly. Or, pull over as soon as you can and refill the tank using a funnel and a jug of DEF.
There is no sense in taking any chances with your expensive truck and diesel engine. The repair costs are quite high and those are bills you do not want to have to pay. Insurance may not cover any of the repair costs if you are at fault.
Some Final Words
New diesel trucks are not the ones used by your father or grandfather. Their models were simple and easy to drive along with having fewer driving worries. Your model has more parts that can fail and more fluids that can empty easily.
Keep your eye on the DEF tank and make sure to keep it filled so you can travel the long distances where DEF at the pump is not available. Also, keep a spare jug of DEF somewhere in your truck or trailer.
That way you do not have to worry about if a gas station has DEF at the pump or not.
