GotQuestions? Lubricants

Q. Does Citgo have a high zinc motor oil that would work well in older flat tappet engines?

There is a lot of concern raised over cam damage in older flat tappet gasoline engines when current gas engine oils are used because of the reduction or elimination of zinc. Would using a diesel oil provide the cam protection these older engines are said to require?

July 7, 2014

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A. If you are using the older gasoline engine for normal operating conditions, a diesel engine oil type formulation does typically provide higher Zinc levels and the higher viscosity-15W-40 will provide extra oil film in addition to the higher Zinc. This answer is premised on the fact that older gasoline engines do not have modern emission/catalytic convertor hardware which is why the zinc and phosphorus levels have been lowered over the years to insure compatibility with the CC hardware.

If the engine is being used for a higher performance demand such as racing or more severe operation a true racing formulation is recommended which typically has higher zinc levels and higher viscosity.

Please provide more detail on the make, model and operating conditions and we can make a more specific recommendation.


In the diesel engine oil category, CITGO offers a high performance diesel engine oil called Mystik JT-8 SHD(Super High Performance) Heavy Duty Engine Oil 15W-40. 

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Author Bio

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Mark Betner

Heavy Duty Lubricants Manager

CITGO Lubricants

Mark Betner boasts 35 years of experience in the lubricants business. As the Heavy Duty Product Manager for CITGO Lubricants he is responsible for initiating and implementing the marketing of new products and human development programs and oversees communications with the media, trade shows and consumer education.

Prior to this, he was a field sales manager and technical training administrator at an independent lubricant company specializing in heavy equipment lubrication.

Mark earned a master’s and bachelor’s degree in both chemistry and biology from Indiana University. He holds a certification from the Society of Tribologists and Lubrication Engineers and is a member of the Truck Maintenance Council.


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