The carbon residue value is considered by some to give an approximate indication of the combustibility and deposit forming tendencies of the fuel.
[1] The Ramsbottom test is used to measure carbon residues of an oil.
Carbon residue is an important measurement for the feed to the refinery process fluid catalytic cracking and delayed coking.
For the test, 4 grams of the sample are put into a weighed glass bulb.
The sample in the bulb is heated in a bath at 553°C for 20 minutes.