I have that exact same car, 1985 Olds Delta 88 Royale Brougham Coupe with the original Olds 5L 307 gas V8
I bought mine on April 29, 1992 with 47K on the clock and a bad trany slipping between 1st, and 2nd. Had a new 400R trany with shift kit and a trany oil cooler put in the next day. Have 168,820 miles on it now.
The valve covers are a bear to keep from leaking oil on GM V8 engines. After doing the valve covers many times over the last 20 years of owning that car I upgraded to new valve covers that were less likely to warp, and I also got a better valve cover gasket from Summit to go with the new valve covers. With the low miles you have with that engine now, for the oil if it were mine I would use GC because it provides great engine protection in hot or cold conditions, and it is great for the main seals and all other seals of that engine. There was a post here on BITOG about Mercedes having forgotten to specify GC for their cars here in the U.S. Those who new enough to use GC had no problems. Those who did not had main seals leak. They had a recall telling owners to use GC and Mercedes had to replace the damaged main seals of the vehicles that GC was not used in for free under the recall.
GC stands for German Castrol, it is Castrol in the black bottle and it will say "European Formula" on the front of the bottle and "made in germany on the back". You can get it at PepBoys, and AutoZone.
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The following is some information about GC:
European Motor Oil - German Castrol 0W-30
We at European Motor Oils are proud to offer our customers, Castrol Syntec 0W-30 European Formula fully synthetic motor oil. Yes, this is GC, German Castrol! Euro Synthetic Oils believes that it is important to stock this very well known and popular motor oil. Simply called "German Castrol by many, Castrol Syntec 0W-30 European Formula, has obtained tons of excellent UOAs (used oil analyses), many of which are reported on the internet forum, "Bob is the oil guy". Castrol Syntec 0W-30 European Formula is engineered to meet the Mercedes Benz 229.5 specification. The 0W-30 viscosity grade is ideal for winter conditions where low temperature pumpability is required. A unique, "low temperature" formulation provides exceptional pumpability in cold weather and allows for unaided engine starts down to -40F. GC is a very stable synthetic motor oil with a cSt of 12(+-) at 100 C. This indicates a "heavier" oil than most 30 weight oils. It is a rather unique oil in that its cSt tends to fall between a 30 and 40 weight oil, though still a 30 weight oil.
German castrol's strength lies in a special oligomer. German Castrol utilizes a very special oligomer. The oligomer is a very cutting edge synthetic fluid sourced from Ketjenlube, a big name additive supplier to the lubricant industry. The actual compound was developed by Kyocera in Japan and the formula was sold to Ketjenlube. So this German blended oil has some Asian heritage . The specific oligomer is a small cut in the overall oil of around 5% or so. It is very thick, with a kinematic cSt @100C viscosity of >200. That is very thick indeed. Heavier than the cSt @100C of many gear oils. This is the content that creates the "cushioning" effect and dampens noise in high shear and rotational zones such as the valve trains. That is why so many German Castrol users comment on how much quieter and smoother their engine seems to run with German Castrol. Read the following link to give you an idea of the effectiveness of Ketjenlube.
View Ketjenlube Polymer Esters Information
CASTROL SYNTEC 0W-30 EUROPEAN FORMULA BENEFITS:
CASTROL GC can be used with confidence in gasoline engine passenger car, new or old, regardless of oil previously used.
CASTROL GC is fully compatible with all conventional and synthetic oils.
CASTROL GC provides superior protection against deposits. Corrosive particles such as acid, soot and oxidized fuel fragments can cause costly damage to critical engine parts.
CASTROL GC contains a Powerful Additive Package that neutralizes corrosive particles, preventing them from grouping together and forming sludge.
Neutralizes acids in your engine that can cause rust and corrosion on vital engine parts such as cylinders, bearings and hydraulic valve lifters.
CASTROL GC meets the world's toughest gasoline engine protection requirements.
CASTROL GC provides Stability & Endurance under extreme conditions (heat, load, speed) that can cause conventional oils to break down.
CASTROL GC delivers the ultimate performance under extreme high-temperature and extreme mechanical loads.
"MADE IN GERMANY" ON THE BACK OF THE BOTTLE. SEE THE OEM APPROVALS BELOW!
