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Castrol vs Mobil 1: Which is Better?

With the growing knowledge of engine oil products, their properties, and the like, it is no wonder comparing top brands, and pleasing choosy consumers have now become the norm. However, the many available oil variants in the market do not make things more convenient. Thankfully, two standout brands easily come to mind. And if you have guessed Castrol vs Mobil 1, you are absolutely right!

Given trusted reputations, similar viscosity grades, and creditworthy products, it is rather difficult to tell which one bests the other. Some choose Mobil 1 over Castrol for its unrelenting performance under extreme weather conditions. Others opt for the latter for its Fluid Titanium Technology.

Deciding between Castrol and Mobil 1 engine oils can be tricky. And superficial factors (like cost and API certification, among others) do nothing to help settle the score. The only way to decide which is better is to read this guide and determine the engine oil brand that works best for you and your vehicle.

Mechanic Holding Engine Oil Container

Castrol vs Mobil 1 – Battle of the Giants

Regardless of available choices, going for a specific motor oil brand will always largely hinge on intended vehicle application and personal preferences (actually, more on the latter). Still, this fact does not make the process of selection easier.

There are so many good options that narrowing down to one or two motor oil variants can be a pain! Fortunately, you can create a checklist of motor oil qualities you deem most important – to help you decide which is better between Mobil 1 and Castrol engine oils.


Oil blends are the easiest to sift through as they depend on vehicle needs. Whether you have a vintage automobile or a more modern sedan, you will require one type of oil blend over the other. For instance, most heavy-duty vehicle owners and lorry drivers prefer synthetic blends. Conversely, high-mileage oils are best for classic, antiquated wheelers.

Most engines are also particular with the compatibility of the additives and conditioners that go into these oil variants, so pay mind to that, too.


Viscosity grade will not be a problem for either Castrol or Mobil 1, as each brand offers consumers a wide spread of multigrade oils from SAE 0W20 to 20W-50.

Similar to choosing the right oil blend for your vehicle, determining the multigrade oil appropriate for your wheeler will depend on outside temperatures in your location. The right oil viscosity could make or break your experience of cruising in Floridian heat or starting your engine during cold mornings.

Change Interval

With the advent of synthetic oils, change intervals have gone from the initial 3,000 miles to every 5,000 to 7,500 miles (annually in some cases). So if you use your four-wheeler as a daily driver, prefer extended oil change intervals, or are simply wired for hassle-free vehicle maintenance, you may want to go for synthetic blends or a fully synthetic variant. Again, both Castrol and Mobil 1 offer these types of engine oils.

Vehicle Application

In determining which is better between Mobil 1 Advanced Full Synthetic vs Castrol Edge engine oils, do not forget to factor in the vehicle’s service schedule and the severity/frequency of its use. Cars would normally be classified as one of two things – a ‘normal service’ or ‘severe service’ transport.

The former category usually requires premium engine oils with intervals of every 12,000 to 25,000 miles. Meanwhile, the latter warrants closer oil change frequencies (typically every 6,000 to 12,000 miles or less). This classification includes fleet vehicles, daily drivers subject to stop-and-go traffic or excessive idling, and wheelers with turbocharged engines.

Engine Mods

A stock engine’s oil requirements versus a high-performance, heavily modified power mill are worlds apart. Mechanics and car savants cannot stress enough how tweaking an engine for horsepower gains can dramatically alter engine oil needs and consumption.

The higher RPMs and more shearing forces brought about by engine upgrades, the higher the quality, additives content, and film strength of engine oil required.


When every other item on the checklist is ruled out, decisions always come down to whether or not one can splurge. While Castrol oil variants are generally cheaper by an average of $10 than the competing Mobil 1 products, both brands are not exactly on the cheapest end of the price spectrum.

Additionally, the savings riders get from their purchase still depend on the type of engine oil they buy. And if they purchase a high-mileage, sludge-cleaning variant, it is likely to cost more than the average rider’s spend.

Synthetic Oil Testing

Since we have discussed top considerations, let us now go over a series of tests conducted by The Petroleum Quality Institute of America – ranging from the simple to the complex – and see how Mobil 1 vs Castrol Edge motor oils fared.

For comparison, the featured results are of SAE 5W-20 multigrade oils. If you are currently torn between the two name brands and one to seek hard proof, this section is for you:

NOACK Volatility Test (ASTM D-5800)

The NOACK Volatility goes beyond determining a vehicle’s MPG by measuring the evaporation loss of lubricants in high-temperature conditions. Per API SN/SN Plus and ILSAC GF-5 specifications, the volatility (motor oil evaporation loss) threshold is 15% maximum.

Meanwhile, other automobile regulatory bodies and engine manufacturers have thresholds lower than this value. For instance, Europe’s ACEA specifications and General Motors set their NOACK volatility percentage to 13% maximum.

In a test where Castrol Edge Full Synthetic was put up against Mobil 1 Full Synthetic, results showed that Mobil 1 lost 8.1%, while the Castrol variant lost 8.8% of its original weight in one hour @ 245.2º C. While the results were within the same bracket, they still showed Mobil 1 has stronger resistance to boiling off at extremely high temperatures than its counterpart.

Note, however, that these results speak for only one specific oil type and should not generalize the performance of other Castrol motor oil products.

Viscosity Index and Cold Crank Simulator Test (ASTM D-5293)

If you think a viscosity test for Castrol Edge vs Mobil 1 Full Synthetic Oils would be futile, think again. Although the multigrade oils sampled here are both SAE 5W-20, an in-depth test will help reveal disparities in oil behaviors during cold startups and operating temperatures.

Engine oil with a higher viscosity index or VI is more likely to maintain a more stable lubricating film across a broader temperature range, making it more preferred for use in areas with changing seasons or fluctuating weather conditions.

Based on the data shown in the table below, you can see who is the clear winner in this round:

ViscosityMobil 1 Full SYNCastrol Edge Full SYN
Viscosity 100º C cST (6.9 to < 9.3)8.78.4
Viscosity 40º C cST49.046.2
Viscosity Index154160
Cold Crank Viscosity at -30º C (Max 6,600)3,9403,701

Total Base Number (ASTM D-2896)

TBN (or Total Base Number) is another facet of lubricants worth looking into. This number signifies a motor oil’s reserve alkalinity – a property lending to its effectiveness in mitigating the corrosive effects of acids, controlling the formation of sludge and other deposits, and handling contaminants over extended periods.

Between the two oil brands, Mobil 1 has a slightly higher TBN value versus Castrol Edge. However, Castrol Edge is more compatible with GDI (gasoline direct injected) power mills due to its lower calcium content that reduces LSPI (Low-Speed Pre-Ignition) frequency.

Detergent Additives and Total Base Number (TBN)Mobil 1 Full SYNCastrol Edge Full SYN
Calcium (ppm)1,125925
Magnesium (ppm)709711
Sodium (ppm)< 5< 5
Barium (ppm)< 1< 1
TBN, mg KOH/g9.08.6

Multielement Determination (ASTM D-5185)

With the help of ICP-AES (Inductively Coupled Plasma Atomic Emission Spectrometry), this test methodology determines additive elements, contaminants, and wear metals contained in used and unused lubricants and base oils, including motor oils.

The said elements are typically present in new engine oil at negligible levels and should not be an immediate cause for concern. However, this is only true if the quantity for each element does not exceed 10 ppm. Otherwise, higher quantities could mean possible contamination from rust, abrasive material, silicone-based sealers, transformer, hydraulic, or old, used oil.

The increase in these elements may also come from packaging, blending, or transit of oil products, making the test all the more significant.

The following tables show the respective AW (Antiwear) additive and contaminant content of Mobil 1 vs Castrol engine oils. Based on the objective of this methodology, it is safe to say that the higher the antiwear additives, the more protected high-friction components are in an engine (since they act as corrosion inhibitors and antioxidants).

Similarly, more contaminants mean a higher propensity for unwanted deposits and premature engine damage.

Antiwear Additives (parts per million)Mobil 1 Full SYNCastrol Edge Full SYN
Phosphorus (600 to 800 -a)737753
Titanium< 121
Contaminants (parts per million)Mobil 1 Full SYNCastrol Edge Full SYN
Silver< 1< 1
Aluminum< 1< 1
Chromium< 1< 1
Iron1< 1
Nickel< 1< 1
Lead< 1< 1
Antimony< 1< 1
Tin< 1< 1
Copper< 1< 1
Potassium< 5< 5
Vanadium< 1< 1
Manganese< 1< 1

Other relevant testing methodologies not included in this section but discussed in length in my article on Amsoil vs Mobil 1 engine oils are as follows:

  • MPG Test
  • Four-Ball Wear Test Para 3 (ASTM D-4172)
  • Flash/Fire Point Test (ASTM D-92)
  • Pour Point Test (ASTM D-97)

Conclusion – Review: Castrol vs Mobil 1 

If you delved into this article expecting a solid recommendation, I will (or may already) have to disappoint you. But if you went into reading this guide for some clarity, I am confident you found what you have been looking for.

With everything shared here, the answer to the question, “Castrol vs Mobil 1: Which is Better?” ultimately still depends on you, the vehicle owner. As long as you understand your vehicle’s needs and factor in your demands as a driver, you won’t go wrong with your decision!