Furnace oil is a dark, viscous residual fuel oil which is obtained by blending residual products from various refining processes with suitable diluents usually middle distillates to obtain the required fuel oil grades. These fuel oil grades are similar in nature and have been marketed under different specifications in various countries. In India it is sold under BIS specification IS 1593-1982 (Reaffirmed 1997), Medium Viscosity Grade 2 (MV 2 – 180 cst FO)

Uses of Furnace Oil are:
1. As fuel for Power Generation in DG Sets
2. As fuel for Boilers/ Furnaces/ Air preheater/ Any other Heaters
3. Fuel/ Feedstock in Fertilizer Plants
4. Furnace oil is a class C product having Flash Point above 66°C. Since this is a residual fuel, there has to be gradual filtration system to prevent the filter choking and fuel nozzles choking. Due to its viscous nature, it has to be heated to improve its flow and to a proper temperature for proper atomisation. Normally gear pumps are preferred to avoid cavitation problems.
Sr. No. Characteristics Grade (MV2) Methods
(i) Acidity Inorganic Nil IS:1448 [P:2]
(ii) Ash Content 0.1 IS:1448 [P:4]
(iii) Gross calorific value, Cal/ gm Not limited but to be reported (typical – 10000) IS:1448 [P:6 or 7]
(iv)  Density at 15°C Not limited but to be reported (typical – 0.950) IS 1448 [P:16]
(v) Flash point (PMCC) °C. Min 66 IS:1448 [P:21]
(vi) Viscosity (Kinematic) at 50 deg C 125-180 IS:1448 [P:25]
(vii) Sediment by extraction 0.25 IS:1448 [P:30]
(viii) Total Sulphur 4 ASTM D 4294
(ix) Water Content 1 IS:1448 [P:40]
(x) Pour Point 27 IS:1448 [P:10]
(xi) Conradson Carbon Residue (CCR) Max - 14 % wt

Light Diesel Oil (LDO) is a blend of distillate components and small proportion of residual components. It falls under class C category with flash point above 66°C. It is marketed under BIS 15770-2008 specification. LDO is used for slow speed diesel engines (below 750 rpm). It is also used in Lift irrigation pumpsets, DG Sets and as a fuel in certain boilers and furnaces where low sulfur fuel is required.

Specification of Light Diesel Oil :
Sl No. Characteristics Requirements Methods
(i) Acidity, inorganic Nil IS:1448 [P:2]
(ii) Ash, percent by mass, Max 0.02 IS:1448 [P:4]
(iii) Carbon residue (Ramsbottom) on 10 percent residue, percent by mass, Max 1.5 (on whole sample) IS:1448 [P:8]
(iv) Pour point, Max IS:1448 [P:10]
a) Winter 12°C
b) Summer 21°C
(v) Copper strip corrosion for 3 h at 100°C Not worse than No.2 IS:1448 [P:15]
(vi) Flash point Pensky Martens, °C, Min 66 IS:1448 [P:21]
(vii) Kinematic viscosity, cst at 40°C 2.5 to 15.0 IS:1448 [P:25]
(viii) Sediment, percent by mass, Max 0.1 IS:1448 [P:30]
(ix) Density at 15°C, kg/ m3 To be reported IS:1448 [P:16]
(x) Total sulphur, percent by mass, Max 1.5 IS:1448 [P:33]
(xi) Water content, percent by volume, Max 0.25 IS:1448 [P:40]
Conforms to IS:15770-2008 Light Diesel Oil Specifications
1 Appearance Visual
2 Colour Visual
3 Cetane Index D 4737 Number 46
4 Pour Point P : 10 °C Note-1
5 Copper Strip Corr. for 3h at 100 °C P : 15 Number 1
6 Distillation Perc.Rec. at 360 °C P :18 Vol % 95
7 Flash Point (Abel) P : 20 °C 35
8 Kin. Viscosity @ 40 °C P : 25 cSt 2 4.5
9 Density @15 °C P : 16 Kg/m3 820 845
10 Total Sulphur D 4294 Wt ppm 350
Note 1: Winter(Nov-Feb) +3 Max,Summer +15 Max
ISO 9001:2008,ISO 14001:2004 & OHSAS 18001:2007 CERTIFIED
S. No Tests Method Unit Limit
1 Kinematic Viscosity at 40°C ISO 3104 mm2/s 2.000-6.000
2 Density at 15 °C ISO 12185 Kg/m3 890.0 max
3 Cetane Index ISO 4264 Number 40 min
4 Sulphur ISO 8754 mass % 1.50 max
5 Flash Point ISO 2719 °C 60 min
6 Acid number ASTM D 664 mg KOH/gm 0.5 max
7 Oxidation Stability ISO 12205 g/m3 25 max
8 Carbon Residue : Micro method on the 10% volume distillation Residue ISO 10370 mass % 0.30 max
9 Pour Point (Summer quality) ISO 3016 °C 0 max
10 Appearance Visual Clear and bright
11 Ash ISO 6245 mass % 0.010 max
12 Lubricity, Corrected wear scar diameter (wsd1.4) at 60°C ISO 12156-1 µm 520 max
13 Recovery @ 360°C ASTM D-86 % Vol To Report