The key difference between RON and MON is that RON describes the behaviour of a fuel in an engine at low temperature and speeds whereas MON describes the behaviour of a fuel in an engine at high temperatures and speeds.
The term RON refers to the research octane number. It is a measure of the performance of a fuel in an engine. We can determine the value of RON by comparing the performance of the fuel and different mixtures of isooctane and heptane in a test engine. The term MON refers to the motor octane number. It is a measure of fuel performance (same as the RON value), but here, we should consider high temperatures and high speeds.
CONTENTS
1. Overview and Key Difference
2. What is RON
3. What is MON
4. Side by Side Comparison – RON vs MON in Tabular Form
5. Summary
What is RON?
The term RON refers to the research octane number. It describes the performance of an engine fuel at low temperatures and low speeds. We can obtain a value for RON by determining the performance of the fuel in a test engine and comparing the results with different mixtures of isooctane and heptane in the same engine. There, the test engine should have variable compression ratio under controlled conditions.
Figure 01: RON Values for Fuel in Service Stations
The typical speed of an engine for the determination of RON is 600 rpm. Also, the RON values of fuels are never less than the MON values. However, there are some exceptions as well.
What is MON?
The term MON refers to the motor octane number. It describes the performance of an engine furl at high temperatures and high speeds. Unlike in the determination of RON, the speed we should consider in determining the MON is 900 rpm. The test engine that we use for this determination is similar to that of RON testing with some exceptions as below:
- A preheated fuel mixture
- Higher engine speed
- Variable ignition timing (to further stress the knock resistance of fuel)
However, this octane rating is not that much common in public because the service stations do not specify the MON rating system.
What is the Difference Between RON and MON?
Although there is no direct connection between the RON and MON values of the same fuel, we can see that the RON value is always higher than the MON value of the same fuel. The term RON refers to the research octane number and MON is motor octane number. The RON describes the behaviour of a fuel in an engine at low temperature and speeds while MON describes the behaviour of a fuel in an engine at high temperatures and speeds.
Summary – RON vs MON
RON and MON are two octane rating systems which we use to express the performance of fuel in numerical terms. The key difference between RON and MON is that RON describes the behaviour of a fuel in an engine at low temperature and speeds whereas MON describes the behaviour of a fuel in an engine at high temperatures and speeds.
Reference:
1. “Octane Rating.” Wikipedia, Wikimedia Foundation, 29 May 2018. Available here
Image Courtesy:
1.’Brighton, MI Sunoco Ethanol-Free Pump Options’By 127driver – Own work, (CC BY-SA 4.0) via Commons Wikimedia