The Best Oil For The Mustang

• Viscosity measures the thickness of a particular fluid where zero is the thickness of water
• Mineral based oils are the “conventional” variety, or the "change every 3,000 miles" oil
• Synthetics are man-made and degrade slower than conventional oils
• The newer the engine, the tighter the tolerances mainly because of advancements in machining
• Newer engines require thinner oils to operate well with these tolerances

The viscosity (thickness) Ford chose for the Mustang is based upon normal operating temperature, or 212° F. The operating temperature is important in your oil choice because oil thins to the correct viscosity at operating temperature. At room temperature (or in the dead of winter), the oil is too thick to be effective. This is why 90% of engine wear occurs at start up. The oil actually goes through a bypass and is returned to the sump until it is sufficiently warmed up.

Let's discuss 10w-30. The 30 represents how thick the oil is at 212° F. The 10w is the "winter" thickness of the oil. In this case, the oil is thicker at operating temperature than when it's cold. Technically there is no difference between 0w-30 and 10w-30 at operating temperature, but 0w-30 is thinner at start up. The thinner oils are for engines with tighter tolerances and to reduce start up wear. If the oil is too thick when it's cold, you won't have proper lubrication, and in the worst case you'll damage your bottom end bearings.

As far as oil wear goes, the reason you do oil changes is contaminants and heat degradation. The repeaded heat cycles break down the oil over time. Once the oil loses its ability to lubricate and draw heat away from the rotating assembly, it's time for a change.

CAFE regulations have directly affected the oil we use in our cars. Engines today use much tighter tolerances than they used to and this means lighter oil viscosities need to be used. 

CAFE regulations are Corporate Average Fuel Efficiency standards that enforce the fact that set averages of fuel economy must be achieved by vehicle manufacturers each year. With that said, it forces manufacturers to crack into the design of their engines to squeeze every last bit of fuel economy as they can out of them.

Lighter oil viscosity allows things to move more freely but some fear that they might not get the lubrication they need out of it and are warned to stick within bounds of the owner’s manual to prevent damage. 

If you want to get some thicker oil in your engine you can use thicker oil without damaging the internals. No, you shouldn’t use purely 30 weight oil in an engine that calls for 20 weight but using a mixture or a ​blend of the two can be done. Racers have been doing this for decades.

API is the American Petroleum Institute which actively works to test and rate oils and other petroleum-based product on the market today. An API rating exists on every bottle of oil. This rating uses a two digit code that tells how it ranks in terms of standards of oil in comparison to engines of a certain time. Mustang owners should familiarize themselves with these ratings and codes to find out whether or not the oil they are purchasing is up to par with their current engine. 

For instance, 5w30 motor oil that falls under one API rating is much different than 5w30 that falls under another. Knowing the difference will tell you which is the better choice for your engine.

Basically mineral oils are your traditional, non-synthetic oils. The common engine oil used in older engines. To achieve the lowest start up viscosity and the correct operating temperature viscosity, additives must be used. These are called viscosity index improvers, or VII. The downfall, however, is heat. When the viscosity improvers degrade, you may end up with 10w-20 oil in your engine instead of 10w-30. Or worse. This is why mineral based oils have to be changed so often. Usually the recommended oil change is every 3,000 miles.

As the name would imply, synthetic oils are artificially made. Not quite. They still require some VIIs, but they go through a different refining process than their mineral based cousins. Since synthetics are more pure, they can endure more between oil changes. They are not as vulernable to heat as mineral based oils, and they can generally go about 7,000 miles between changes. Although synthetics may have the same viscosity rating as mineral based oils, they offer better lubrication and protection even at start up.

All oils come from the earth, and this may leave you wondering if the brand of oil you are using really matters. Guys will swear by Royal Purple, Amsoil, Mobil, Lucas, Redline, Valvoline and even Motul; each telling you why the oil they prefer is the best. The truth behind oil is that it is typically designed for a specific use. 

For example, some oils are meant for daily drivers, while others are intended for use on the track. How do you know which one you should be running and when? All the previous listings we discussed are strong reputable brands that have offerings for just about any application between them. However, understanding the pros and cons of each will help you decide which oil is best for you and your car. For specialty vehicles, Royal Purple, Lucas, Redline, and Motul will be found on the top of the list. The blends they use are what keep them stable in the abusive, high heat environment of racing engines which is a pro. The cons are the offerings of viscosity variances and conventional blends by these brands is limited, if even available. Also, depending on your location, they can be hard to come across.

As for which is the best among them, it’s all in the eye of the beholder. Royal Purple is typically crowned king for track use, though the contenders on the list are very much in the same rankings. Brands like Valvoline and Mobil do offer synthetic bends and offer great track options. Though they aren’t commonly held on high by the masses in this department. Where they truly shine is in their selection and abundance. Both can be found nearly anywhere with just about any viscosity or blend one could want. They also are much more economical, in most cases, which makes them the perfect choice for daily drivers.

If you just picked up your Mustang from a private seller, a mineral based oil with a lot of detergents might not be a bad idea to clean out the engine, assuming the previous owner wasn't as much of an enthusiast as you.

You own a Mustang. Odds are you’re going to modify it and it at the track. After particular modifications and in the right settings you know that the suggested octane levels of the fuel changes. Which brings up an interesting question - what about the oil? Every engine calls for a specific oil viscosity. Oil viscosity is directly impacted by temperature; therefore engine temperature does have an effect on the way the oil behaves. 

So when do modifications to the engine impact oil viscosity? Well, any one particular mod may only narrowly raise the operating temperature of an engine. If oil temperature does rise, oil coolers can be added along with a bigger radiator to keep things stable. Though, testing out higher oil viscosity may be worth tinkering with. It generally will not go too far though. For instance, an engine running 5W30 in stock form may benefit from a slightly higher viscosity like that of 10W30. Some even prefer to simply combine the two to create their own blend. Upgrades that affect any engine tolerances, like rotating assembly upgrades, will impact viscosity in a whole different manner. They can raise or lower the right level of viscosity to different extents and the engine builder will have to point you in the right direction.

Oil is a funny thing that is directly affected by temperatures. In fact, the oil viscosity measurements tell you right on the bottle how the oil will behave in winter temperatures.  What if It gets too hot though? 

Say you’re driving your Bullit Mustang in 110 degree temperatures? Should you run thicker oil? Well, yes and no. Too thick of a viscosity can hurt the internal workings but using a blend of the next step up from the OE required oil is not a bad idea.  

Drivers regularly tamper with the oil they run in their engines when they’re at the track but seldom throw in a thicker oil by itself. You’ll find they add a quart or two of higher viscosity oil in place of the factory oil to achieve the viscosity they are looking for. On the street for daily driving, you might not even have to change the oil because the engine isn’t being pushed, but during races it is crucial.

With a freshly built engine, it’s easy to get a bit ahead of yourself and overthink the additives and oils that need to be used. Though, there is a break in period and you will need to address this properly. 

As far as the oil goes, you should stick to whatever the manufacturer of the engine or the machine shop recommends. Veering from the recommendation can result in a blown engine out of the gate. If the engine needs to be broken in, you will need to use the appropriate break in additives and run the engine through the break-in cycle.

While an engine is fresh, it’s good to do frequent oil changes out of the gate and dissect the filters. You want to do so to look out for metal shavings in the oil. Skipping these steps can mean that early signs of a faulty build will be missed or pars that need to be broken in, like the cam, can be worn away rapidly.