opening Pandora's Box... extended German Castrol.

[j_mac]

Would like everyone's opinion.
I've got a '99 Mustang GT that I used German Castrol in the last oil change.
I've put 12,000 miles on this oil. I've had to add a couple quarts to make-up what has been lost.

What do you guys think?

Have I overextended the oil change? Should I flip out and change it today?

I wasn't too worried about it since the GC looks like conventional oil does with 5000 miles on it in this car. It seems to have stayed cleaner 2 times as long as conventional oil.

 

[Johnny]

If I were going to run it as long as you did, I would have pulled a sample at 5K just to see what it looked like. I run nothing past 10K without sampling first.

 

[Scienceman]

Change it and do a UOA.

 

[bretfraz]

A couple makeup quarts is, what, about 40% of the oil capacity? I think you're OK for now but I'd change it anyway.

The neptune spacebears M1 analysis a few years ago showed that even a little bit of top off oil will improve additives to keep the oil going along fine.

The only way to know for sure is do a UOA and see what is really going on. You might want to pull one now, do a OCI, then see if you can't take your OCI even further next time.

 

[hate2work]

Originally Posted By: j_mac


I wasn't too worried about it since the GC looks like conventional oil does with 5000 miles on it in this car. It seems to have stayed cleaner 2 times as long as conventional oil.


I'm sure you know by now that you really can't tell much by just looking at the oil. I have seen reports of oil that still looked good, but upon analysis it was spent. If this was my rig, I'd change the oil. GC is a good oil, but I don't think it was designed for extended drains, at least it's not advertised as such.

 

[Quattro Pete]

Originally Posted By: hate2work
I'm sure you know by now that you really can't tell much by just looking at the oil.

Exactly. Color has nothing to do with anything.

Quote:
GC is a good oil, but I don't think it was designed for extended drains, at least it's not advertised as such.

It carries Mercedes and BMW LL specs, so that makes it a long life oil, IMO. BMW allows intervals as high as 20k miles on LL oil, depending on driving conditions. With that said, I too am hesitant to run it past 10k miles.

 

[d00df00d]

How big is the sump in that 'Stang?

 

[Billy_D]

Originally Posted By: Troy_Built
Change it and do a UOA.


+1

 

[Quattro Pete]

Originally Posted By: d00df00d
How big is the sump in that 'Stang?

5 quarts, I think.

 

[d00df00d]

In that case I would guess that 12k miles is a stretch but not impossible. Engines have certainly survived worse.

 

[38sho]

don't they take like 7 or 7.5 qts?

 

[Geonerd]

Just another opinion...

I'd change it "before too long," but wouldn't lose any sleep in the meantime.

IMO, color does have some bearing on an oil's health. The more blow-by engine produces, the sooner soot and combustion by-products will darken and acidify the oil. Oil that is still reasonably clean after 12K is less likely to be running low on TBN.

I believe GC's TBN starts at around 10. It should be fine.
Any chance you'll run a UOA?