A main aspect of quality in biofuel is its ability to auto or self ignite, which initiates combustion with low input or energy, however, it still needs to remain safe and at a reasonable level. This is made more efficient by increasing the compression ratio of the engine, increasing the autoignition ability and engine efficiency. This can be tested by placing a flask in a temperature controlled oven, with a thermocouple to measure temperature, and slowly injecting the substance to observe when it spontanouesly ignites.