When purchasing motor oil and any other fluid for your car, it is tempting to look for the biggest brightest sign and go with that. However, there has been a lot of changes in the automotive maintenance industry in the past decade. Some of the top companies have fallen to legacy brands while other newcomers surprise with performance and price.
Still, when it comes right down to it, you want to trust the health of your car to a company who has the experience to serve their customers well for decades. Two such companies are Castrol and Mobil 1, who are actually subsidiary companies of some of the largest petrol corporations in the world. That said, how do these 2 giants stack up when compared to one another. Does anyone have an edge, and if so, for what products?
Castrol as a brand should be considered your classic “blue collar,” working man’s brand of motor oil. Regardless of how they market their products, Castrol motor oils have a tendency to favor casting a broad net rather than focused targeting. As such, this means that there is a good chance that one of the Castrol motor oils will work especially well for your vehicle. On the other hand, if you do have a unique arrangement, Castrol may not necessarily be the first brand that you turn to.
This means that if your vehicle requires no special manufacturer’s maintenance, Castrol is a great option.
A Company History
The Castrol company actually started as a small start-up in the 19th century in London as CC Wakefield & Co. From those humble beginnings, Castrol was born, though the name itself is simply a portmanteau of Castor Oil which was one of the primary ingredients in the original formula. These days, Castrol is actually a subsidiary company of the petroleum giant, BP. That said, these days, Castrol actually provides high-quality lubricants to virtually every market–including aeronautical space engineering for NASA. However, the primary crux of the company relies on the sales of high-quality consumer-grade motor oil for the average driver.
Most Popular Brands
Castrol likely blurs the line between actual brands and particular lineups, where you could reasonably say there are 2 brands of motor oil: Edge and GTX. However, due to the way that Castrol markets their products, they often include niche motor oil products as separate brands. To make matters simple, just think of the GTX brand as their “standard” brand and Edge as Castrol’s “premium” brand. This is especially true given that most of the different niche “brands” appear in both GTX and Edge formulas. It is also worth remembering that even between these two brands, most Castrol motor oil still targets a more general driver.
As Castrol’s premium brand of motor oil, the Edge lineup predictably performs better than the GTX lineup. That said, there is a good chance a most of this increase in performance is due to the fact that the Edge brand comes exclusively in full synthetic formulas while the GTX brand has only a single full synthetic product in its lineup. It is also worth noting that of the “niche” products that Castrol also categorizes as individual brands, the only shared type between the Edge and GTX brands is the High Mileage type. This is also where you will find Castrol’s motor oil for supercars.
Despite not being the “premium” brand of the Castrol motor oil lineups, the GTX is not inherently a bad motor oil. In fact, the GTX lives primarily in the province of non-full synthetic oils. Outside of a singular product, the GTX covers synthetic blends and conventional oils more than anything else. It is also worth noting that most of the “niche” brands in the Castrol lineup are ultimately GTX products. The GTX caters to a number of older vehicles as well as those which run on diesel fuel.
GTX brand products are generally not full synthetic oils, but they still contain the wealth of the additives that Castrol products are known for.
This begins the “niche” brands of which the Ultraclean is technically within the GTX umbrella. Even more interesting, the Ultraclean “brand” is part of the synthetic blend lineup that Castrol carries–something it can boast over Mobil motor oils. As the name suggests, the GTX Ultraclean is designed to clean out the sludge and gunk in an older or poorly cared for engine. In this regard, it is not nearly as strong as a true engine flush, but it still offers far more potent detergents and dispersants than your average “cleaning” motor oil. This is especially good for Castrol in particular as Mobil does not focus as much on restoring as much as they do on maintaining.
Castrol GTX Magnatec
From Castrol’s perspective, once you have cleaned and flushed your engine out, you then need to provide your newly clean engine with protection. That is where the Magnatec niche “brand” comes into play as it is specifically designed to help condition, repair, and strengthen the raw metals of your power system. It is also worth noting that the Magnatec lineup within the GTX brand is also the only full synthetic GTX motor oil that Castrol sells. Regardless, the Magnatec motor oil comes not only with the common antiwear and rust-inhibiting agents, but it also has magnetically charged materials that fill in the damage left from time past.
Having been around for over a century comes with some advantages and one of the biggest is connections. Castrol definitely takes advantage of the connections it has been able to build over the past century by working hand-in-hand with the makers of its products when developing their own. As such, virtually every Castrol motor oil is recommended within its given sphere of influence by car makers that push the boundaries of their own automotive engineering feats. One area that BP could stand to work on is its involvement in combating some of the issues their products can cause–an area where Mobil holds a distinct advantage.
Mobil as a company may have once been a company “of the people,” but these days, the company seems to focus more on the upper echelon. This is because Mobil does not really offer too many options nor make much effort to cater to owners of engines that are obsolete or in poor condition. As such, this may not be the brand that is best for a large number of drivers. What is interesting is that Mobil is able to maintain competitive pricing with Castrol despite having a smaller targeted market share. On top of that, Mobil offers a bit of breadth that Castrol lacks in terms of applications.
Mobil has been a major player in the petroleum markets pretty much since its founding over a century ago. Originally a vacuum oil, Mobil was eventually purchased by Standard Oil which begins the long process of Mobil becoming the lubricant powerhouse that it is today. Of course, after the dissolution of Standard Oil, Mobil was owned by Jersey Standard which eventually renamed itself Exxon. It is worth noting that Mobil was once a much larger brand than it is today, though it still holds a fairly sizeable share in the motor oil market–especially for any performance-heavy application.
Most Popular Brands
This is Mobil’s premium brand, and they have gone all in with this direction, pouring the overwhelming majority of their research and marketing into developing this brand over their others. In fairness, the Mobil 1 brand does truly live up to its billing as a premium brand of motor oil, but this will also exclude a fair number of consumers from the brand. If your engine is not newish and in decent condition, the Mobil 1 brand may not be the best choice–at least, not until you get the engine in better condition. Still, if you have anything resembling a new model or high-performance engine, this is the brand to use.
Mobil Super seems like a cheap way to make your standard line of oils seem more impressive. This is made all the more obvious with the fact that the brand does not contain many products and focused more on non-full synthetic motor oils.
The Mobil Super brand is not a bad motor oil, but the company does not put nearly as much effort into formulating these products as they do their flagship brand.
This shows up most prominently in the sheer disparity of products in each brand, but the Mobil Super brand does not even have much proprietary technology included in their formula like Castrol.
This is definitely a unique brand in that it is the only brand between the 2 companies that are specially formulated for diesel engines of a commercial grade or higher. This means that farmers, truckers, and construction crews will have little choice if they have to choose between Mobil and Castrol. That said, Mobil goes a step further by ensuring that they offer both conventional and full synthetic formulas of this heavy-duty motor oil. Still, even Mobil only offers 2 different models, so the pickings are still fairly slim. On top of that, the Delvac brand is designed more for highway driving than industrial or agricultural purposes.
“Niche Models,” in this instance, refer to various common types of marketing groups that different motor oil companies all use but for which there is no objective standard. Some of these niches force a standard of sorts by limiting their application, but by and large, each company is free to define what any of these niches mean for their particular products. As such, this is where you will begin to see the different companies, and even their requisite brands, begin to separate and distinguish themselves. If you are looking for a place to truly judge the different motor oil companies, the niche markets are where you will find the biggest gaps.
This is one of the more common types of motor oil sold, but it is generally only necessary if the engine has not been maintained. Keep in mind that most motor oils contain some detergent and dispersant additives, but a “cleaning” motor oil will contain far higher concentrations and potencies.
Between Castrol and Mobil, Castrol has the clear advantage of having put significantly more research into their cleaning motor oils. Mobil does not generally focus on engines in poor condition and instead assume the engine is in good condition when using their oil, though they do include cleaning agents in their oils.
This is by far the most common type of motor oil model sold considering most people are interested in maintaining the investment of their car more than they are pushing it the limits. There are a wide range of different additives included to preserve your engine, but antiwear, anti-friction, and rust-inhibitors are the most common. In terms of performance preservation, Mobil 1 will continue its dominance.
However, for engines that use conventional motor oil, the Magnatec additives put Castrol neck and neck for the consumer-grade market. Still, Mobil and Mobil 1, in particular, have a tendency to provide better preserving qualities than Castrol.
These are fairly straightforward and fairly slim in terms of the offerings. This has a lot to do with the fact that more and more motor oils are being made to work equally well with both diesel and gasoline engines. That said, there are still plenty of older diesel engines out there that will not work with the full synthetic motor oils that can work with either fuel. In this instance, neither company really has the advantage for consumer-grade diesel engines, though Mobil 1 does offer a performance diesel oil. On top of that, Mobil also makes a diesel motor oil to work specifically for commercial trucks with more than 3 axles.
This is a fairly common and popular “niche” category to the point where most motor oil companies market it as a specific brand. However, a quick look will usually show that the particular high-mileage “brand” actually falls under one of the company’s major lineups. Regardless of how it is marketed, high-mileage motor oils all have a couple things in common. For one, this model will need to include both cleaning as well as preserving agents–and often in equal measure.
Another quality most high-mileage motor will have is viscosity additives to make it easier on an older engine. Mobil’s brand of Mobil 1 High-Mileage motor oil is actually the highest-rated high-mileage motor oil.
This niche of motor oil includes all formulas which are specifically designed to work with high-performance engines. This can include anything from a local Honda tuner car all the way to professional racing vehicles. Between the 2 companies, Mobil easily outpaces Castrol with their Mobil 1 brand providing numerous entries in the Performance niche markets. In fact, Mobil 1 Performance motor oils offer a full range of options that are specifically suited for the particular grade of performance engine you own. As such, the driver of a tuner car should not use the same Performance motor oil that a driver of a supercar should use. It is also worth noting that Castrol does not cater to racing motors within their consumer brands.
Despite what the name may seem to imply, “Heavy Duty” motor oils are not really meant for consumer-grade vehicles. This means motorcycles, cars, trucks, and SUVs may be put through their paces, but still do not require Heavy Duty motor oil. It is also important to distinguish between Performance and Heavy Duty oil as the former is meant for tuned engines.
Heavy Duty motor oil is meant for the various pieces of industrial equipment that consumers often own.
Tractors and other types of agricultural equipment or other types of heavy equipment will use Heavy Duty oil. The Mobil Delvac brand of motor oil is the only one sold to the public between either company.
Motor Oil Viscosity Types
It might be a bit surprising to find out, but the 2 companies actually have a bit of difference between the viscosity of oil that they offer. In fairness, a bit of this has to do with the various brands, types, and niches, but not all instances of difference are because of this obvious reason. Instead, it seems that the general “theme” of each company shines through with the most prominent example of this being the sheer number of cold-weather options that Castrol offers compared to Mobil. It is also worth noting that Castrol has more hot-weather motor oils too with Mobil having a narrower range of viscosities.
- The First Number – The first number will tell you what the viscosity of the motor oil at freezing temperatures will be. The higher the number the better the oil will be able to maintain its viscosity, even if temperatures drop to freezing lows. It is worth noting that you can actually add pour-point depressants to the oil to increase its performance in cold-weather conditions. Still, with a motor oil with a natural freezing viscosity rating of 20, Castrol has a distinct advantage over Mobil in this market. That said, 20wXX motor oil is often not necessary, even if you live in the northern part of the country.
- The Second Number – Whereas the first number tells you how the motor oil will respond in cold-weather conditions, the second number tells you what to expect once the engine gets hot. Just like with the first number, the higher the second number the better, though at this point the risk is of the oil being too thin not too thick. Once again, Castrol offers the widest range of viscosities for hot temperatures with a 10w60 motor oil. That said, Mobil is the company with the new Japanese-style 0w16 motor oil. This motor oil is amazingly good for fuel economy, but it requires significant additives to account for its thinner viscosity.
The “types” of motor oil refer to what their primary ingredients are made of. While technically full synthetic motor oils started as a “pure” petroleum product, their ingredients undergo enough changes that they are no longer considered “true” petroleum products. As such, you have 3 main types of motor oil based on their true petroleum ingredient content. Motor oils with only a petroleum base are conventional motor oils while full synthetics have no true petroleum products. Synthetic blends are a mixture of the two, though it need not be a 50/50 mixture, and the degree of proportion will differ from brand to brand. Mobil has a tendency to favor the synthetic side of their mixtures, though Castrol is no slouch in that department either.
This is quickly becoming the most common type of consumer motor oil sold, and it is not hard to see why. Full synthetic motor oils outperform both conventional and synthetic blends in virtually every head-to-head comparison. The only thing that can hold a full synthetic motor oil back compared to the other types is compatibility–though that is quickly becoming a thing of the past as well. Regardless, when comparing Castrol and Mobil in the full synthetic category, Mobil takes a fairly commanding lead with most of their products centered on this type.
As the name suggests, a synthetic blend will combine ingredients from both conventional and synthetic motor oils. This allows the oil to work better with older engines while still offering an improved performance over pure conventional motor oil. This is the market that could be wide open were it not for the fact that Castrol, with a superior conventional motor oil lineup, is able to generally produce better synthetic blend motor oils as a result. That said, this category is probably where the 2 companies are the closest and it could very well be a toss-up–unless you need a deep-clean.
This is the least common type of motor oil sold for consumer automobiles today, but there are still plenty of older engines on other types of equipment that require conventional motor oil. It is also the only type of motor oil that can be used for engines past a certain age. This type of motor oil is made with “pure” petroleum products alone as well as whatever additives the company includes. It is not as good at providing long-term lubrication, but it is often less expensive. Castrol offers more and better options within the conventional oil market.
Which one to recommend for different engines (application chart)?
|Standard Conventional||Castrol GTX|
|Standard Synthetic Blend||Mobil Super|
|Standard Full Synthetic||Mobil 1 Annual Protection|
|Performance Full Synthetic||Mobil 1 Racing|
|High Mileage Synthetic Blend||Castrol GTX High-Mileage|
|High Mileage Full Synthetic||Mobil 1 Extended Performance High-Mileage|
|Restore Synthetic Blend||Castrol GTX Ultraclean|
|Restore Full Synthetic||Castrol GTX Magnatec|
|Diesel Conventional||Castrol GTX Diesel|
|Diesel Full Synthetic||Mobil Delvac 1 ESP|
As we can see, Mobil and Castrol are both excellent companies which offer great products within their brands’ lineups. That said, they are not equal by any measure of the word and instead are better suited for different tasks. If you have an older model engine or are looking to prolong the life and efficiency, then Castrol is likely a better choice. Of course, if you take fastidious care of your vehicle and are looking to get more performance from it, Mobil is the clear victor. Mobil is also the better option for most diesel applications and the only option for heavy-duty motor oil.