Thinking back, I had a similar situation in a Fiero GT I had about 8
years ago. It never burned any oil until I started using Mobil 1 in
which case I seemed to loose about 1 quart between oil changes(every 3K
miles). This was on a fully broken in modified engine. I had switched
to synthetic because I wanted to get rid of the cold start lifter tap
that was being caused by the HP valve springs and high ratio rockers I
had. It solved that problem, but other than that I couldn't notice a
difference between synthetic or carbon based oil. In anycase, one thing
that was mentioned to me at the time was the fact that many racers don't
use synthetic because, with the lack of a carbon base, you don't get a
perfect seal around the piston rings. I was told that the carbon base
in standard oils actually increase the sealing of your piston rings.
I think it's possible that you may be experiencing the same problem due
to the fact that Castrol "full synthetic" is actually manufactured with
a "highly refined" carbon base(but legally they can still call it
synthetic). An artical in Car & Driver recently by patrick bedard
brought this little bit of news to my attention. Aparently, from what I
remember, Mobil 1 is the only truly full synthetic out there so you may
just be blowing right by the rings due to the addied lubrication of it.
Al
Patrick and Kelly Engram wrote:
>
> Here's more for you who've followed this thread. I decided to go and
> check the oil level in her
> vehicle again, since it has been almost 2K since the 2nd oil change with
> Mobil 1. The oil was as dark
> right now as I've ever seen the Castrol Syntec after 7500 miles, and it
> was also 1/2 qt. low. This would
> translate into almost 2 full qts. low by the time it gets to the 7500
> mile interval. I measured the oil
> I drained after the first Mobil 1 oil change, and it was barely 2 qts
> out of a 4 1/4 qt capacity (no oil light
> or low oil pressure gauge reading!?)
> Commenting on some questions that have been raised since I first
> started this up-
> No, the engine does not smoke at all. But my '92 Dakota 318 never
> smoked, but it still "use" a quart between oil changes even at 60,000
> miles. And it has absolutely no oil leaks.
> Clean-the inside of the motor is extremely clean, no varnish, sludge, or
> discoloration. The valves have
> to be adjusted every 15,000 miles, so I get a chance to see the inside
> quite frequently.
> So, what led to the drop in fluid level/consumption and the dark
> color?
> I took up someone's suggestion and contacted the place to get your oil
> tested.
> And the synthetic saga continues
> Patrick
> ps-Anyone want 4 1/4, er uh 3 3/4 qts of Mobil 1 oil, slightly used, for
> free? Come to Maryland and bring a jug, cause I'm ready to switch
> back. And, even worse, (and additional Dak content) I also switched
> from Castol GTX that I used on my last Dakota to Valvoline on my R/T
> (trying to please the Nascar sponsors) Maybe I ought to switch back?!
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