Castrol Power1 XR77 vs A747

Both of the contenders are two-stroke racing engine oils with XR77 being designed for motorcycle and kart engines while its competitor is manufactured solely for water-cooled two-stroke engines built-in into road racing machines.

An ultimate XR77 is a pre-mix racing 2-stroke engine oil centered on fully synthetic technology.

It is an economical choice in terms of both price and fuel consumption in terms of density.

Due to its lower pouring value, this engine oil is a better option to avail in cold weather.

A racing lubricant, A747 is low ash, partial synthetic lubricant. It also comprises special additives to avoid choke slides from sticking in damp weather conditions and can be used at a 40: 1 fuel/oil ratio.

Besides being relatively more viscous, its viscosity changing ability according to temperature is also high making it more adaptive to environmental change.

Compared to A747, XR77 is a more economical choice and consumes less fuel. Moreover, XR77 is suitable for cold weather conditions and is fully synthetic engine oil. Whereas, A747 is best suitable for high-temperature conditions, is partially synthetic, less viscous, and is suitable for racing engines only.

Comparison Table

SpecificationsPower1  XR77Power1  A747
Oil TypeFull syntheticSemi-synthetic
Fuel / Oil Ratio40: 140: 1
Product typeRacing engine oilRacing engine oil
Engine Type2 Stroke Engine2 Stroke Engine
Cost of 1 Liter16.28 $18.30 $

Features & Benefits


  • Incomparable high-speed/high-temperature lubrication
  • Assurances optimistic control in an internal combustion engine.
  • Avoids choking slides from sticking in pouring weather conditions.


  • High lubrication formulation to avoid subjugations in high-speed conditions
  • Allows tuners to tilt their engines to an extreme side
  • Ensures constant engine power during the race.
  • Noticeable plug flickering and piston crown reserves to enable fine race tuning
  • High levels of reserves and good tones provide outstanding readability on all non-leaded fuels.
  • Controlled lubricant in damp weather
  • Easily mixes with racing gasoline



XR77 is an oil specially formulated for pre-mix use in racing 2T automobile and cart engines. This is not suitable for normal road driving.


A747 is deliberated for racing engines only. It is not suitable for ALS (Automatic Lubrication Systems) distributes a specific amount of lubricant across the engine while it’s operating and should not be mingled with any other mineral, vegetable, or synthetic oil.

Viscosity Comparison

Another most important property of a fluid lubricant includes the friction of the lubricant liquid, the load-bearing capacity of the lubricating film, its resistance to the onset of movement relative to the moving parts, and its sealing ability.

As we can see in the table below that the kinematic viscosity of A747 is relatively higher than its competitor at hot and cold temperatures.

It clearly shows that A747 will flow more easily than its contender and hence will consume less fuel to circulate.

The result of temperature variation between the kinematic viscosity and the temperature is measured by a unit less parameter called the viscosity index.

Its value is inversely proportional to the change in the value of kinematic viscosity which means that the greater the value of the index, the lesser the changes will occur.

                                            ParameterPower1 XR77Power1 A747
Kinematic Viscosity @ +40 °C112 mm/s²178 mm/s²
Kinematic Viscosity @ +100 °C14.9 mm/s²19.7 mm/s²
Viscosity index138127

The kinematic index of XR77 is higher than its contender which means that XR77 would be less affected by temperature change (environment change). So the winner would be A747 since its environment adaptability would be relatively higher than its competitor.

Endurance in Extreme Temperatures

XR77 is a remarkable option in cold weather while its competitor would be a better choice in high-temperature conditions.

This can be analyzed by two parameters known as the flashpoint and the pour point.

Flashpoint is used to determine a specific temperature at which the fumes of engine oil would catch fire. The flashpoint of A747 is comparatively higher.

It will last comparatively longer in high-temperature conditions.

 Whereas, the pour point determines the temperature at which an engine oil would freeze and will lose its flowing ability becoming frictionless.

The pour point of XR77 is comparatively lower which shows that it will freeze later than its contender.

ParameterPower1 XR77Power1 A747
Pour point, °C-24-21
Flashpoint, °C223240

The Density of the Oil

Density is an important fluid characteristic. The density of the oil and temperature are indirectly proportional. As the oxidation advances, the density of the oil increases. Overall, density plays an important role in how the lubricant works, as well as how the machines work. Most systems are designed to pump a fluid of a certain density, so as the density begins to change, so does the pump’s performance. As the lubricant density increases, the fluid thickens. This increases the time it takes for the particles to come out of the suspension.

ParameterPower1 XR77Power1 A747
Density @ 15°C (Relative)0.913 g/ml0.93 g/ml

The density of A747 is higher and its consistency is thicker as compared to its competitor.

The fuel is consumed more by the pump to circulate for a thicker lubricant.

This shows that XR77 is more economical in terms of fuel consumption and a better choice comparatively.


Castrol Power1 XR77;

  • is fully synthetic engine oil.
  • is less costly than its contender.
  • has fewer temperature alterations due to the higher value of the kinematic index.
  • Suitable for two-stroke engine oil.
  • is a remarkable option in cold weather.
  • is comparatively more economical in terms of fuel consumption.

Castrol Power1 A747;

  • is a semi-synthetic engine oil.
  • is a relatively better choice for high-temperature conditions.
  • Has relatively high kinematic viscosity at high as well as low temperatures.
  • Is suitable for a two-stroke racing engine.
  • Is relatively more adaptive to environmental change.