1999 Lexus LS400.
Car has been running quiet and beautiful.
So yesterday I start it and I hear what sounds like a very loud lifter.
The sound gradually diminishes as they often do.
Next time I start it there is no problem, no noise.
I am used to lifter problems that gradually come on as a car ages.
This was sudden, and vanished just as suddenly.
This is something I have never seen before.
Does it make sense? Any idea what is going on?
I don’t think your engine uses hydraulic lifters, so that noise might be a sticking valve; and yes, that can be intermittent.
This could make sense.
The car was stolen and went too long between oil changes (8000 miles).
So, after this happened, I put in some CD2 oil detergent,
and an oil change will come next.
Maybe there was no permanent damage.
Proper diagnosis for a proper cure, I thought it was valves, turned out to be a bad tensioner.
You should probably get a shop to look at it and notify your insurance company of an amended claim. I assume the theft was reported?
The sound never returned. After adding the CD2 and doing a bit of highway driving, the oil became much more
black. I assume that there were deposits built up that were removed. I suppose the oil outlived its additives.
Anyway, the deposits may have brought on the lifter problem
Going 8,000 miles between oil changes once isn’t going to hurt the car unless you have an oil leak and too much leaks out because of the extra miles.
CD2 is snake oil - it doesn’t do anything useful.
Wrong. CD2 replaces detergents which may become depleted in old oil.
No, CD2 says it replaces detergents which may become depleted in old oil. People have done chemical analyses on it and discovered it’s basically just 20W oil.
So, it turns out that CD2 oil detergent has been discontinued.
What do people recommend as a substitute oil additive when
extra cleaning is called for? One idea seems to be Sea Foam.
Anyway, “just change the oil” replies are not needed.
so noted. I’ll go elsewhere then. 
If you don’t want the correct answer, why are you asking the question?
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