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Home » Public Forums » GMCnet » Castrol Oils (Another attempt to find the best for the GMC)
Castrol Oils [message #274791] Thu, 02 April 2015 11:02 Go to next message
Gatsbys' Cruiser is currently offline  Gatsbys' Cruiser   United States
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Registered: August 2014
Location: Illinois
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There is a new kid on the block being advertised fairly heavily on the Satelite networks.
This new oil is Castrol GTX MagnaTech. It's claim to fame is it has an ability to retain lubrication after the engine comes to rest. When the engine is started, the lubrication residue protects the engine wear surfaces until the oil warms up and is in full circulation of the system.

I posed a question to "askBP.com" about the use of Castrol GTX MagnaTeck in our older engines.

( If anyone has thoughts feel free to offer comments. If there is an oil that can be used without need for the additive, this could be a benefit and save space in the RV )

This was their response..>>>>>>>>>

Today at 9:55 AM

Good morning


Thank you for contacting Castrol North America.


Castrol always recommends following the guidelines of your manufacturer to determine the recommended grade and API specific to your application. This information can be found in your owner's manual, or by contacting your OEM directly.



Classic cars with flat tappet cam engines represent a special case in regards to engine oil lubrication. These engines have valve train configurations that require elevated levels of zddp (zinc dialkyl dithiophosphate) anti-wear for proper protection of the flat tappet camshaft and its lifters. Insufficient concentration of zddp will lead to premature wear and failure of the camshaft and lifters. Current GF-4 and GF-5 fuel economy grade engine oils are designed for extended life of the catalytic convertors in modern passenger cars and have industry mandated limitations on the amount of sulfur and phosphorus within the oil. Hence, the concentration of zddp is limited (approximately 850 ppm of zinc).



Castrol EDGE SAE 5W-50 has been reformulated to have a boosted level of zddp (1300 ppm) to help protect flat tappet cam engines in classic cars. This engine oil is a full synthetic,

has excellent cold temperature properties, and has a high temperature viscosity (SAE 50) that is suitable for use in many classic car applications. The vehicle owner must determine that a SAE 50 multigrade oil is appropriate for the engine (consult owner manuals, OEM service depts., classic car mechanics, car clubs, or other reliable sources). For flat tappet cam engines, the zddp concentration required for proper protection is dependent on valve spring pressure and engine rpm. As spring pressure or rpm increase, the concentration of zddp must also increase. Due to the wide variety of engine configurations found in classic cars, each engine should be considered on a case-by-case basis. EDGE with SPT SAE 5W-50 can be used with confidence in flat tappet cam engines with mild or moderate

valve spring pressure such as flat-heads or stock engines up to the mid-1990s. The vehicle owner must monitor the mechanical condition of the valve train and cam, especially in muscle cars, hot rods, modified engines, or engines with elevated valve spring pressure or rpm levels.

All-out race engines with flat tappet camshafts have high valve spring pressures and rpm levels and have special zddp requirements and viscosity requirements for bearing and piston skirt protection. CastrolEDGE SAE 5W-50 may be considered for use in mild racing activities such as vintage club races that use gasoline fuel.

Please note that Castrol GTX MAGNATEC is rated API SN and is not suitable for these applications.

Thank you again for contacting Castrol, we value your patronage!

Castrol Consumer Relations

1-800-462-0835

Re: Castrol Oils [message #274807 is a reply to message #274791] Thu, 02 April 2015 14:45 Go to previous message
roy1 is currently offline  roy1   United States
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Registered: July 2004
Location: Minden nevada
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That is good information I use Mobil 1. 15/50 but the castrol 5/50 would be a good choice also with 1300 ppm zink additive.

Roy Keen Minden,NV 76 X Glenbrook
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