High Idle Diesel: Is High Idle Bad For Diesels? (Guide)
The key is when to use it. There are many features on a diesel engine that many RV owners do not know or are unsure of how to use. One of those features is called the high idle and it is there to help you when you have to idle your RV longer than a few minutes. Not everyone uses this feature.
The high idle feature is there to help prevent wet stacking. This is where the cylinder temperature is not high enough to burn all the fuel. That unburnt fuel then slides down into the oil pan diluting the oil and in turn creating excessive engine wear.
To learn more about high idle and what it is used for, just continue to read our article. It has the information you want to know about so you can use this feature at the best possible times. You do not need it at a red light or a short stop on the side of the road.
High Idle Diesel
What is a High Idle Switch?
The high idle switch is the device that lets you idle your RV or truck at a higher rate of RPMs than your RV, etc., would normally idle with the switch turned off.
It is usually operated through your cruise control on the left side of the steering wheel. To use the high idle, you need to set your parking brake, do not touch the gas or the brake pedals, and your vehicle cannot be moving.
Before you get going again, do not forget to shut the high idle switch off. You do this by pressing the brake, pushing the cancel button, releasing the parking brake, or you shift out of park or neutral.
You can also turn it off by turning the cruise control button to off.
What is High Idle Used For?
You will get differing opinions on this switch. Some people do not see the need for it while others think it is the perfect addition to a diesel engine. It is up to you to decide which side of the debate you are on.
What the high idle switch does is protect your truck’s or RV’s engine. If all the diesel fuel is not burnt up in the cylinder then it can mix with the oil. When that happens the oil brings the fuel into the oil pan, diluting it.
Once the oil gets diluted, you have less lubrication available and your engine can wear out faster. Plus, this device helps keep the oil pressure up to around 1000 PSI to make sure there is enough protection for all your engine’s moving parts.
Is High Idle Bad For Diesels?
No, it is not. It is a device that has many benefits to it. Two are as already mentioned above. It is to protect your engine from any possible damage that can be done by not completely burning the fuel.
Another benefit is that it helps warm your RV or truck up faster on cold mornings. Then keep it warm because you are still getting plenty of hot air in the cab as it idles.
We have not seen anything that says, this device is bad for a diesel engine. The reason for that is that diesel fuel needs to burn at higher temperatures. The high idle helps to do just that.
You may not need this device as it may be a novelty than a must-have device. There are many diesel owners that do not use it nor want to have it installed on their vehicle.
What RPM Should a Diesel Idle At?
You should hear different opinions on this as well. What makes this discussion confusing is that there are so many older diesel engines still on the road today. What their requirements are is different from what modern diesel engines require.
In this modern era, the ideal idle rate is about 1000 RPM. This keeps the oil pressure where it should be. Anything lower will also lower the oil pressure which may eventually harm the engine.
Some people say that a diesel engine needs to idle at 500 to 600 RPM and anything lower is not good for it. But that may be for the older diesel engines. A diesel KIA Sportage SUV is happy at 750 RPM and it is 20 years old.
If you are not sure after reading this, talk to a trusted diesel mechanic. Get the straight story from those who know these engines the best
Why Does My Diesel Truck Idle High in Park?
There are different reasons for this scenario. One is that you may have set or had your mechanic set the idle air control valve too high. This is usually operated by a screwdriver and someone may have turned it a little too far.
Just get another screwdriver and with the engine on, lower the idle speed by turning that screw slightly. Another reason is that the transmission is no longer engaged.
Once you put the gear shift into park you are removing resistance which makes the engine work a little easier and faster. Or your air control valve is dirty or clogged. This keeps it open at a higher level and it just needs a good cleaning to close it again.
A final reason is that your oil is low and you need to add more or your air filter is dirty and needs to be replaced. All of these reasons can influence how fast your engine idles when you are not driving.
6.7 Cummins Automatic High Idle
This is a device that has been on all Dodge trucks since about 2002. But it is not an automatic start device. It has been said that you need the dealer to turn it on first before you can use it.
There is a special screw that operates the high idle switch and many people do not own that screwdriver. Once activated, then you simply use your cruise control device to turn it on.
After doing that, then you should see your Dodge truck idle at about 1100 RPM, which is high enough to keep that oil pressure up there and burn all the diesel fuel.
It may be best to talk to your dealer about this. They will be able to tell you how to use it correctly as well as when you should use this device. One thing is for sure, it is not meant to be used when you are at a stop sign or stop light.
Cummins 3-Cylinder High Idle
You can’t drive when your truck is in 3-cylinder mode. There would be no power to drive with. But that does not mean you cannot take advantage of this feature.
What the 3-cylinder mode does is loads the engine, making it work thus creating more heat. This mode only operates after 2 conditions are met. The first condition is that the intake air temperature is below 15 degrees F.
The second condition is that the coolant temperature is below 160 degrees F. There is a big debate about whether 3rd gen trucks with smarty software can enable this mode or not.
According to one expert, this feature was only available for 2nd gen trucks. However, over the years this may have changed and more trucks can use 3-cylinder mode if it has been installed in your vehicle.
This is something you have to check with your dealer. But for older trucks, this is the case.
How Long Can You High Idle a Diesel Engine?
There does not seem to be any real time limit. If you have deep pockets and can afford the fuel you may be able to let the diesel engine idle for 10+ hours. The only thing you are losing is fuel.
If you have taken notice of the many big rigs over the years, you will see them idling for hours on end. Nothing happens to their motors. Those engines are built by the same companies that build engines for Duramax and other trucks.
If you want a figure, you should be able to let your diesel engine run for 8 hours with the AC and have no problems. What you would need to do this would be a high idle kit.
Get one installed and you should be able to idle for hours without any worries, especially if you lost your hotel room or all the rooms are taken when you arrived. The high idle will make sure all the fuel is burnt so you would not have to worry about wet stacking or other engine problems.
Some Final Words
The high idle device is not for everyone. There are quite a few owners who see no advantage to having one installed and many that do, never use it. You would have to decide if installing and using this device will fit your driving needs.
It does cost over $200 to install so think twice about doing this.
