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Best Motor Oil For Muscle Cars

Deciding on what is the best motor oil for muscle cars depends on a variety of factors, such as whether the temperatures outside are cold for most of the day or whether it’s summertime. Other factors would include how hard the engine is run, measured in the number of RPMs reached. How hot the engine is running is yet another factor.

Determining Viscosity

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First, let’s discuss the basics concerning viscosity grade. Let’s take the example of a 15W50, which could be a typical motor oil viscosity used for a muscle car engine. The letter “W” after the 15 tells the viscosity requirements of the engine oil when it is cold. More specifically, the 15W rating of the oil actually means that it must meet certain parameters at cold operating temperatures. In the case of the 15W50, using the 50 weight viscosity as an example, motor oil that is rated 15W will flow more easily at colder temperatures than a heavier 20W rated motor oil.

Let’s next discuss the 50 weight part of the following three motor oils, which are 15W50, 20W50, and a straight grade SAE 50. The SAE organization has stated that an SAE 50 weight engine oil should have a viscosity above 16.3 centistokes at 100 degrees Centigrade, but less than 21.9 centistokes. Additionally, at 150 degrees Centigrade, it should have a higher shear rate viscosity minimum of 3.7 centistokes.

AMSOIL Z-ROD® 10W-30 Synthetic Motor Oil

Translating this means that the three grades of motor oil of 20W50, 15W50, and SAE 50, should all meet these SAE requirements. Understand, this does not necessarily mean that they will react in the same way, but they all should meet these requirements regardless of whether they are designated as 50 weight engine oils.

Multi-Viscosity or Straight Grade?

You may be wondering whether it would be better to use multi-viscosity engine oil or a straight-grade engine oil when deciding what is the best motor oil for muscle cars. Before choosing, it is best to study in detail the various oil specification datasheets you can get. Analyze those, and then compare the information you have learned with what your engine needs, and then choose the motor oil that will fit your requirements.

AMSOIL Z-Rod 10W-40.
AMSOIL Z-ROD® 10W-40 Synthetic Motor Oil

The better question to ask yourself is how shear-stable the engine oil is based on the environment it will be run under. Shearing means how much viscosity could be lost during a severe operation. Shearing is quite possible if the engine is run quite often at high RPMs. So, you want to look for a motor oil specification that shows as little shear loss as possible during testing. The lower the number, the more shear-resistant and the less viscosity loss the oil will have.

Muscle cars obviously will have high performance, high horsepower engines, and their owners will on occasion like to let loose and feel the full power of their engine. This means high RPMs and these high RPMs will expose the motor oil to the potential of shearing down the oil’s viscosity. Maintaining the oil’s designed viscosity is the most important factor in maintaining the oil’s ability to protect your engine.

AMSOIL Z-Rod 20W-50.
AMSOIL Z-ROD® 20W-50 Synthetic Motor Oil

Please note that there are various levels of quality and performance when motor oil manufacturers decide which viscosity improvers they will use to maintain the motor oil’s ability to stay in grade. In simplistic terms, the lower the price of the motor oil, the lower the quality of the viscosity improvers used, and the easier and faster the oil will shear down its viscosity.  Typically, your high-performance, higher-priced motor oils will use very shear-stable, stay-in-grade VI improvers that are not easily sheared under high RPMs.

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The old adage “you get what you pay for” can definitely apply to the cost of the oil and the quality that you pay for. In real-world situations, once an engine reaches full operating temperatures, you need an oil that can withstand the temperatures and not shear down the viscosity. On the discussion of whether to use a multi-grade or straight grade motor oil, one of the few benefits of running a straight grade motor oil is that it is far more difficult to shear down a straight grade since a straight grade does not contain VI improvers. It has its uses, but it is a far more limiting oil if you’re using it in your vehicle for everyday use.

AMSOIL 5W-50 Signature Series.
AMSOIL Signature Series 5W-50 Synthetic Motor Oil

Straight-grade oils lend themselves more to race cars. During warm temperatures, hot climates, and hot operating temperatures, a 50 weight motor oil will stay in grade under those conditions. The downside to running a straight 50 weight is exposed under cold climates or when the engine is cold. It takes longer for a heavy SAE 50 to be delivered throughout the engine and most definitely when the temperatures start to get cold outside and near the freezing point, a 50 weight engine oil could be problematic because it is too thick to protect the engine from cold temperatures.

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When discussing multi-grade motor oil, they are the better choice for colder climates and even normal climates when starting up your engine when it is cold.

AMSOIL 10W-20 Signature Series.
AMSOIL Signature Series 5W-20 Synthetic Motor Oil

Multi-grade engine oils flow much faster during cold starts, thus protecting those critical engine parts far quicker than straight-grade motor oils. It is important to note that it has been proven that the majority of engine wear for any automobile occurs during the cold starts of an engine because it takes a certain amount of time for the oil to flow throughout the oil passageways and reach all the engine parts.

What is the Best Motor Oil For Muscle Cars?

AMSOIL Signature Series 10w-30.
AMSOIL Signature Series 10W-30 Synthetic Motor Oil

The best solution to cover all your muscle car requirements when it comes to protecting your engine is to pick a shear-stable multi-grade engine oil that flows quickly to the engine parts when the engine is cold and if you live in a cold climate. Plus, a multi-grade oil that is shear-stable will handle the high temperatures regardless of how extreme the engine is run. The key is to choose a shear-stable oil.

AMSOIL 5W-30 Signature Series.
AMSOIL Signature Series 5W-30 Synthetic Motor Oil

That narrows your choice down to specialty brand lubricant manufacturers such as AMSOIL. Since a company such as AMSOIL offers only 100% synthetic-based motor oils, that alone helps in dealing with cold and hot temperatures. Add to that their use of heavy-duty additives and shear-stable VI improvers, and your muscle car engine will be protected with the best motor oil for muscle cars when you decide to let loose with its full power.

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