# Oil change interval with Castol Syntec



## seadoo2006 (Feb 4, 2008)

Hey,
Just wondering on a 2001 GTI VR6 what my proper oil change interval should be running Castrol Full Synthetic. I autoX and do road racing every so often, but the majority of my miles are from my daily commute of 40+ miles...
I have been doing every 3000 miles so far and was just wondering if I am wasting my money and should go to 5000 miles or a different interval.
I live in northern Ohio, so the climate is 80+ average summer and the possibility of snow from about October through May.
Thanks in advance.


----------



## shipo (Jan 3, 2006)

*Re: Oil change interval with Castol Syntec (seadoo2006)*


_Quote, originally posted by *seadoo2006* »_Hey,
Just wondering on a 2001 GTI VR6 what my proper oil change interval should be running Castrol Full Synthetic. I autoX and do road racing every so often, but the majority of my miles are from my daily commute of 40+ miles...
I have been doing every 3000 miles so far and was just wondering if I am wasting my money and should go to 5000 miles or a different interval.
I live in northern Ohio, so the climate is 80+ average summer and the possibility of snow from about October through May.
Thanks in advance.

I'd say that you are definitely wasting your money with anything less than five or six thousand mile OCIs. That said, every engine, every driver, and every driving environment is different, and that means that the only way to be sure of the proper OCI for _your_ oil, used in _your_ car and driven under _your_ driving conditions is to have some of _your_ used oil analyzed.
http://www.blackstone-labs.com/
Without any scientific analysis, there is no way you can actually determine what is the optimal OCI, and anybody who tells you different is just offering his or her opinion. That said, if said opinion came from a VW engineer who designed and built your engine, then I might actually listen (but I'd still verify that via a UOA).










_Modified by shipo at 10:18 AM 8-25-2008_


----------



## seadoo2006 (Feb 4, 2008)

http://****************.com/smile/emthup.gif for the information, but I don't think I really need to spend the money to get my oil analyzed. I was more just looking to see what others running Castrol Syntec were averaging on their OCIs. I've always felt safe was better than sorry, but for the price of oil and the fact that synthetics are longer lasting, I was looking to see what I might be able to extend it out to safely.
Anyways, thanks again for your comment. I may just have to do that.


----------



## franz131 (Apr 13, 2008)

*Re: (seadoo2006)*

Not all Syntecs are created equal.
Make sure you use the 5w40 version that meets VW 502 00 specs. Particularly if you want to run the European oil change interval.


----------



## saaber2 (Jul 15, 2008)

*Re: Oil change interval with Castol Syntec (seadoo2006)*

IMO with syntec 5w40 3000 miles is ultra-safe, 5000 miles is safe, 7500 is probably o.k. but I would want at least on UOA with TBN analysis to verify that 7500 is o.k. , 10,000 probably pushing it but if UOA w/tbn shows it is o.k., then it is o.k. 
As a general rule of thumb, if the TBN of the oil is less than 50% of the starting TBN, it is time to change the oil. 
Also remember that manufacturers have marketing factors in their recommended OCI's. For example Porsche is now saying 20,000 miles on most cars. I have had the factory-recommended M10W40 analyzed on a boxster s with a 9 quart sump and the TBN was less than 50% of starting TBN at around 8500 miles. None of the porsche technician and service writers I have talked to use that 20k interval and they recognize it is based on "low maintenance" marketing B.S. So when VW says 10k OCIs, don't take that to the bank.


----------



## tjl (Mar 24, 2001)

*Re: Oil change interval with Castol Syntec (saaber2)*


_Quote, originally posted by *saaber2* »_So when VW says 10k OCIs, don't take that to the bank.

If you really want to be sure, take oil analysis at various intervals to see how long the oil will last under your driving conditions.
An interesting read about oil analysis and oil lifetime, although the car used is not a VW:
http://neptune.spacebears.com/....html
http://neptune.spacebears.com/....html
http://neptune.spacebears.com/....html


_Modified by tjl at 8:44 AM 8-26-2008_


----------



## shipo (Jan 3, 2006)

*Re: Oil change interval with Castol Syntec (saaber2)*


_Quote, originally posted by *saaber2* »_As a general rule of thumb, if the TBN of the oil is less than 50% of the starting TBN, it is time to change the oil.

Never in all my years of studying oil and UOAs have I ever seen a recommendation that says that if the TBN is half, it's time to change the oil. The other side of the coin is that most every comment I've read from professional oil analysts recommends an oil change when the TBN reaches anywhere from 1.5 to 1.0 (and they all agree that 1.0 is too low).
Regarding Mobil 1 0W-40, the oil starts with a TBN of about 12.0, and when it's half gone, it's still registering a 6.0 on the TBN scale, more than many motor oils start with when brand new. I have absolutely no issue with running that oil many thousands of miles beyond the 6.0 TBN level.
Another thing to consider is that TBN depletion does not happen on a linear scale; that 8,500 miles in your Boxster brought your TBN down to half in no way implies that at exactly 17,000 miles, your TBN would be 0.


----------



## saaber2 (Jul 15, 2008)

*Re: Oil change interval with Castol Syntec (shipo)*


_Quote, originally posted by *shipo* »_
Never in all my years of studying oil and UOAs have I ever seen a recommendation that says that if the TBN is half, it's time to change the oil. The other side of the coin is that most every comment I've read from professional oil analysts recommends an oil change when the TBN reaches anywhere from 1.5 to 1.0 (and they all agree that 1.0 is too low).

It is pretty widely accepted by a lot of oil experts. f.e. the following quote from Doug Hillary who knows more about M1 than you or I will never know. "Running with a TBN 1.9 may be problematical in a low use engine. It is generally accepted that in the event of no TAN being taken, a TBN of around 50% of the virgin product is the desirable condemnation point. If it was my vehicle I would change the lubricant now if the TBN is less than 40% of new"
http://www.bobistheoilguy.com/...22116
There are countless other example from experts but I don't have time to find them all. Of course you can use when TAN = TBN which is another common rule of thumb (but not that many people test both TAN and TBN) or use whatever you want.

_Quote, originally posted by *shipo* »_Another thing to consider is that TBN depletion does not happen on a linear scale; that 8,500 miles in your Boxster brought your TBN down to half in no way implies that at exactly 17,000 miles, your TBN would be 0.

I never said it was linear or that his tbn would be zero at any mileage.


----------

