Dielectric vs Conductive Grease

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Bright Raven

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This is a controversial subject. I have used both greases but it is confusing. When I changed the coil packs on my old F-350, callmefence said to put dielectric grease in the boot. I looked in my shop and had some gray colored electric grease that I put on the 220 wires going into the box. I decided to go to NAPA and get a grease just for the coil packs. It looks like vaseline - clear. The guy at NAPA said it not only insulates but conducts.

What is the scoop?

PS: can you use the conductive grease on your trailer plug?
 

greybeard

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Bright Raven":14asiykm said:
This is a controversial subject. I have used both greases but it is confusing. When I changed the coil packs on my old F-350, callmefence said to put dielectric grease in the boot. I looked in my shop and had some gray colored electric grease that I put on the 220 wires going into the box. I decided to go to NAPA and get a grease just for the coil packs. It looks like vaseline - clear. The guy at NAPA said it not only insulates but conducts.

What is the scoop?

PS: can you use the conductive grease on your trailer plug?
True dielectric grease is an insulator. Much of the grease today labeled dielelectric is not real dielectric grease but a combination of conductive enhancement and water repellant.
Probably depends on how much current/voltage is present and required. If the circuit is just being used to light a 12v bulb, it won't make much difference, as 12v is considered high voltage in an automotive accessory (non-ignition) circuit nowadays. We've all pulled a brake light bulb out of an older vehicle and seen the white OEM grease on the bulb and in the socket. That's conductive grease used to ensure a good contact on the ground side of the bulb. The old trailer brake controllers, (like most 'electronics' of the time) used some form of physically adjustable rheostat that changed the voltage. They were kind of funky as you moved the lever back and forth depending on load you were pulling. The rheostats themselves had no lubricant along the slide area--you've seen them I'm sure. A serrated copper bar that provided different resistance as you moved the slide along the bar. The rheostats of this type generally went from zero resistance to infinity resistance, with infinity basically meaning the unit passed zero voltage and zero resistance passing the full battery/charging system voltage.

The current ones, use integrated circuit boards that are very sensitive to voltage and current and I would be hesitant to use a true dielectric on the prongs of the connectors of a vehicle that had a modern brake controller. The controller can not pass as much voltage to the brake as it is intended to do as set up by the design. On the other hand, a true conductive grease gobbed into the trailer wiring receptacle can pass voltage from the tail light/brake light circuit to the prong of the brake circuit. Moderation....

Engine and transmission sensors are another place you have to be careful about using dielectric or conductive grease. Usually, a one wire sensor like most O2 sensors, you want to use conductive grease and not dielectric, as the sensor uses the threaded portion of the sensor to get a good source to ground.
 

wbvs58

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Bright Raven":2fxvhu1q said:
This is a controversial subject. I have used both greases but it is confusing. When I changed the coil packs on my old F-350, callmefence said to put dielectric grease in the boot. I looked in my shop and had some gray colored electric grease that I put on the 220 wires going into the box. I decided to go to NAPA and get a grease just for the coil packs. It looks like vaseline - clear. The guy at NAPA said it not only insulates but conducts.

What is the scoop?

PS: can you use the conductive grease on your trailer plug?

That's a big statement from the fellow at NAPA Ron, it conducts as well as insulates, I would think it was one or the other.

Ken
 

Atimm693

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It is an insulator. On a properly fitted connector, the interference of the pins or tabs scrape away the grease and the connection is made. It's purpose is to repel water and contaminants.

A lot of guys like to smear that stuff on any connection they take apart, but I find it's usefulness to be pretty limited. 99% of automotive connectors are sealed and best assembled clean and dry. It's a bad idea on trailer plugs because of the dirt and grime it collects.

It is a good idea on high voltage ignition parts, the grease discourages arcing and lubricates the boot and terminal for easy removal. You would not want to use anything even remotely conductive for this purpose.
 
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Bright Raven

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wbvs58":29pxpav0 said:
Bright Raven":29pxpav0 said:
This is a controversial subject. I have used both greases but it is confusing. When I changed the coil packs on my old F-350, callmefence said to put dielectric grease in the boot. I looked in my shop and had some gray colored electric grease that I put on the 220 wires going into the box. I decided to go to NAPA and get a grease just for the coil packs. It looks like vaseline - clear. The guy at NAPA said it not only insulates but conducts.

What is the scoop?

PS: can you use the conductive grease on your trailer plug?

That's a big statement from the fellow at NAPA Ron, it conducts as well as insulates, I would think it was one or the other.

Ken

You got a point. Those properties are contrary to each other.

Thanks to the comments above, I got it figured out. Good information here.
 

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