Both these oils are fully synthetic where HMX is only compatible with gasoline engines having 75,000 miles plus covered, while HPS can be used with both the petrol and diesel type engines.
HMX is a catalytic converter-friendly oil, having a great number of detergents to clean the engine from slurry. It delivers great resistance to high-temperature oil oxidization, reducing oil consumption. It allows higher kinematic viscosity at medium temperature along with lengthier oil change distances.
HPS has an excellent anti-wear ability due to the presence of strong anti-wear additives inside it. It offers higher kinematic viscosity at higher temperatures along with a higher viscosity index since it has viscosity transformers to reduce the impact of temperature change on its kinematic thickness. Its oil change frequency is lower due to its decent TBN.
Table of Contents
Comparison Table
| Terms | Royal Purple HMX (5W-30) | Royal Purple HPS (5W-30) |
| Type of oil | Full Synthetic | Completely Synthetic |
| Type of engines cpmpatible | Gas | Petrol and Diesel |
| Viscosity grades available | 10W-30, 5W-30, 5W-20 | 10W-30, 5W-30, 5W-20, 10W-40, 20W-50 |
| ILSAC | Unavailable | Unavailable |
| API | SP, SN Plus, SN | SL |
| Price per Quart. | 9 $ | 19.95$ |
| Oil change over rate (Km) | 19,000 | 19,000 |
| ACEA | Unavailable | E9 |
Contrast of Wear-off Reduction Security
Without any lubrication, the engine parts will skate with other parts and wear off. Engine oils provide the necessary lubrication by forming an oil coating across the turning engine parts. This coat reduces the metal with metal contact and hence lessens the resistance which causes the wear to the engine parts.
This whole process is accomplished by the anti-wear and tear additives which are responsible for forming the oil film.
HMX uses phosphorus and zinc as its primary anti-wear additives, but their quantities are lesser in comparison to that of its competitor.
However, its secondary anti-wear additives molybdenum and boron are present in higher quantities. Even though its secondary anti-wear additives are in higher quantities, it loses to its colleague in terms of anti-wear protection owing to the lesser numbers of basic anti-wear and tear additives.
HPS has higher quantities of primary anti-wear additives phosphorus and zinc while lower quantities of secondary additives molybdenum and boron are present in it. The Primary additives are effective enough to boost the anti-wear capabilities of this oil higher than that of its peer.
| Oils (5W-30) | Zn Concentration (ppm) | P Concentration (ppm) | B Concentration (ppm) | Mo Concentration (ppm) |
| Royal Purple HMX | 951 | 866 | 20 | 139 |
| Royal Purple HPS | 1296 | 1096 | 8 | 99 |
Thickness Assessment
The kinematic viscosity of an oil is its ability to readily transfer the momentum through its layers and particles. A greater kinematic thickness indicates better flowing characteristics of an oil.
The viscosity index of an oil is the measure of its resistance to change in kinematic thickness owing to a temperature change.
Pour point temperature is the certain temperature below which the oil will lose its flowing capability under the control of gravity.
HMX has a higher kinematic viscosity at 40°C, but its kinematic viscosity decreases to a lower level at 100°C in comparison to the other oil. Due to the sharp decrease in its kinematic thickness, its viscosity index is lower than its rival. It also has a higher pour point temperature, meaning it will freeze before its counterpart in cold weather.
HPS has a smaller kinematic viscosity at 40°C than its peer but retains much of its kinematic viscosity at 100°C (greater than its counterpart) which results in a higher viscosity index of this oil. Its pour point temperature is also lower than its competitor which means it will freeze after the other oil in freezing season.
| Oils (5W-30 Grade) | Kinematic Viscosity at 40 o C (mm2/s) | Kinematic Viscosity at 100 o C (mm2/s) | Viscosity Index (VI) | Pourpoint tempersture (Degrees Celsius) |
| Royal Purple HMX | 62.8 | 10.9 | 166 | -45 |
| Royal Purple HPS | 56.25 | 11.03 | 193 | -51 |
Catalytic converter Working Evaluation
The catalytic converter performance is affected by the ash that is formed by the phosphorus and zinc compound’s burning which are present in engine oil as anti-wear and tear additives. A lesser amount of these extracts will ensure a better catalytic converter’s performance.
HMX has a lower number of these additives, that is because it is better fitting to be utilized with converters.
HPS, on the other hand, has a higher level of these extracts which will form a higher quantity of ash. This ash will poison the catalytic converter, undermining its performance.
| Oils (5W-30 Grade) | Zn Concentration (ppm) | P Concentration (ppm) |
| Royal Purple HMX | 951 | 866 |
| Royal Purple HPS | 1296 | 1096 |
Slurry Build-up Lessening Assessment
The moisture, dirt, and other contaminants combine with the oxidized oil to create a thick fluid called sludge. This sludge is very harmful to the engine as it can stop the tubes taking oil and will lead to engine seizure. Detergents are included to motor oils to prevent the build-up of sludge.
HMX uses both magnesium and calcium as its main detergents. Its sodium and calcium levels are lower in comparison to its counterpart, but magnesium intensity is higher.
The combined effort of calcium and magnesium allows it to better reduce the slush build-up in comparison to its peer. A higher level of anti-foam, agent sodium is included in this oil.
HPS only uses calcium as its main detergent. Its calcium and sodium quantities are higher comparatively, whereas magnesium is available in lower quantity. Owing to the lesser quantity of magnesium its sludge reduction ability is lower than the other oil. Sodium is present in lower quantity, hindering its anti-foam ability.
| Oils (5W-30) | Na Concentration (ppm) | Mg Concentration (ppm) | Ca Concentration (ppm) | Si Concentration (ppm) |
| Royal Purple HMX | 2 | 1315 | 2326 | 6 |
| Royal Purple HPS | 5 | 13 | 3158 | 3 |
Evaluation of Engine Oil Burn-off Security
The flash point temperature of an oil is the high temperature upon which the fumes of that specific oil could be burned non-constantly with a spark.
A higher flash point temperature indicates that oil has a lesser amount of light particles, and it will evaporate at a snail’s pace when introduced to a high-temperature environment.
HMX has a greater flash point temperature which means that it is less volatile and will provide better oil burn-off protection.
While HPS, having a lower flashpoint temperature indicates a relatively higher number of lighter molecules present in this oil which causes it to evaporate rapidly, decreasing this oil’s burn-off security.
| Oils (5W-30) | FlashPoint Temperatures (Degrees Celsius) |
| Royal Purple HMX | 230 |
| Royal Purple HPS | 216 |
Oil Switch Occurrence Difference
The base extracts added in the oil are measured as Total base number (TBN). The base additives deactivate the toxic acids made through the incineration process, resulting in decrease in their quantity. An oil with a significantly lower TBN is considered unusable. Hence a better TBN indicates oil could be employed for a lengthier duration of time (Oil change interval).
Both these oil have a similar oil exchange period of 19,000 Km due to comparatively minor difference in their TBN. Where HMX has a slightly decreased while the HPS has a slightly higher TBN.
| Oils (5W-30) | TBN mg of KOH/g |
| Royal Purple HMX | 8.9 |
| Royal Purple HPS | 10.11 |
Price Differences
The price of HPS is almost double than that of HMX which is available at 9 US dollars per Quart while HPS is available at a price tag of 19.95 US dollars per Quart. HMX is the higher cost-useful oil compared to its counterpart.
Quick Summary
- Both these motor oils are fully synthetic where HMX is for gasoline engines while HPS is for both gasoline and diesel engines.
- HPS is available in a higher number of viscosity grades than its counterpart.
- HMX is a catalytic converter-affable oil.
- HMX is better at reducing the sludge build-up.
- HMX has the higher oil burn-off security.
- HPS provides higher engine wear-off protection.
- HMX has the higher kinematic viscosity at 40°C while HPS has the higher at 100°C alongside with the greater viscosity index and a lesser pourpoint temperature.
- Both the oils offer equal oil shift gaps.
- The price of HPS is higher while HMX is highly cost-effective.