Another suspension question. I'm putting new strut inserts all around. I went with the KYB's. Question is... Should I fill the void in the strut tube with an oil or not?

I know there are lots and lots of discussion about such things, but what's the current prevailing thoughts?

I know that KYB says not to, but what's the downside?

Other than voiding potential warranty returns (which isn't going to happen anyway), what would such downside be?

And you intent is... Corrosion prevention? I certainly would not attempt to fill the void with oil as it can make a vacuum when trying to remove them as well as attract and capture dirt.

Actually, at the top of my list is heat dissipation. The strut converts kinetic into heat, and that heat needs to get completely out of the strut assy. Air is not a great conductor. Now granted, I'm not autocrossing the car and I don't expect that I'll be overheating my struts, but that's why I asked about the downside. If there's no downside, then why not just fill the void?

Corrosion prevention would be important as well as I've heard reports of inserts rusting into place inside the tubes.

I'm not worried about hydraulic vacuum locking the insert inside the tube. Just take off the gland nut and pour it out. That's what I did when I took the previous inserts out.

And you intent is... Corrosion prevention? I certainly would not attempt to fill the void with oil as it can make a vacuum when trying to remove them as well as attract and capture dirt.

I can't see a downside to adding oil, a vacuum can be defeated by draining the oil out and KYB shocks don't fit that tightly anyway. I've had to remove inserts that have rusted solid in the tube before and it's not fun. It only takes an 1 oz to do the job.

I used KYB inserts and also debated the use of oil. I looked at the gland nut and since there is not a seal on the KYB unit decided not to fill with oil. I did put a oz or two in the housing to keep it from rusting. Been about a year and no problem that I can see.

I was concerned that if filled the oil might leak out and would make a mess. This advice and $2 will get you a small soft drink, maybe.

It's in the fsm so it can't be that bad. I also gobbed lots of grease on the top to hold back any oil and to prevent corrosion.

Its really not necessary for heat dissipation. The oil is required in the FSM because the strut tube itself is the outer body of the shock and the oil you pour in is the actual damping medium. I just spray some Kroil, Rost-Off or other anti-corrosion penetrating oil inside the strut tube and coat the shock body with grease.

I oiled my KYBs a year (and a few thousand miles) ago, despite them saying not to. I figured "why the hell not". No issues thus so far.

Like jcb I didn't brim the tubes, it only takes a very small amount of oil.

Edited March 1, 201411 yr by Captain_Zeros

With the switch to encapsulated shock mechanisms it makes you wonder if you shouldn't drill a small hole in the strut tube to let moisture out. Condensation happens everywhere, along with leakage from the gland nut area and it will sink to the bottom of the oil pool at the bottom of the tube. If I was doing my mine again I'd probably drill a hole (undecided as to where) then grease up the shock body with heavy grease before installation. Leave the strut tube dry and the heat from the hub will probably keep it dry.

Just thinking. With KYB's or Tokico's the system is not the same as designed.