Product Tested

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Rural King Supply

Company and Product Information

Corporate Office:
Rural King Supply
4216 Dewitt Ave.
Mattoon, IL 61938


Rural King Supply is a farm supply store. The company was founded in 1960 and operates 80 stores in ten states in the U.S., including(Illinois, Indiana, Kentucky, Tennessee, Ohio, Michigan, Missouri, Pennsylvania, West Virginia, Florida. The heart of Rural King is the corporate office, distribution center and flagship store, located in its city of origin, Mattoon IL.

Rural King's stores offer such products as livestock feed, farm equipment, agricultural parts, lawn mowers, workwear, fashion clothing, housewares and toys, and its private label motor ois marketed under the RK brand.


The Petroleum Quality Institute of America (PQIA) is an independent resource for information and insights on the quality of lubricants in the marketplace. Our mission is to serve the consumer of lubricants by randomly sampling and independently testing lubricants taken from the field. Test results are posted along with the brand names on the PQIA website. This webpage provides an analysis on the brand detailed below.

The following are the test results for the sample examined.

Rural King Heavy Duty Diesel Engine Oil SAE 15W-40

Product: Rural King Heavy Duty Diesel Engine Oil
Viscosity grade: SAE 15W-40
Labeled: API CJ-4/SM

Packaged by Warren Oil Company, Inc., Distributed by Rural King

Purchased at: Champaign, IL

Date of purchase: 1-5-2015


Website(s): www.ruralking.com

Test Results and Assessment:

The results of the tests conducted on this sample meet the SAE J300 specifications for the SAE Viscosity Grade listed on the product label, and are consistent with the listed API Service Categories.


bottle icon Physical Properties pass
Elemental Analysis pass
Labeling warning

Note: Although laboratory tests alone cannot be used to establish if engine oil meets an API Service Category, they can be used to determine if it doesn't.

PHYSICAL TESTS (click for test details) - a Standard Rural King
TBN, mg KOH/g (ASTM D2896) 9.7 
Viscosity @ 100ºC, cSt (ASTM D445) 12.5 to 16.3 15.5
Viscosity @40ºC, cSt (ASTM D445) 118.2
Viscosity Index (ASTM D2270) 138.0
Viscosity @-20ºC mPa s (cP) (ASTM D5293) 7,000 Max 5715
Volatility, mass % loss, 1 hr, @ 250ÂșC (ASTM D5800) 13 Max -c 12.8
ELEMENTAL ANALYSIS (click for test details) - a, b
Calcium 1209
Magnesium 854
Phosphorus, ppm 1,250 1147
Zinc, ppm 1258
Molybdenum,  ppm 47
Barium, ppm <1
Boron, ppm 1
Silicon, ppm 5
Potassium, ppm <5
Manganese, ppm <1
Titanium, ppm <1
Copper, ppm <1
Sodium, ppm <5
Vanadium, ppm <1
Silver, ppm <1
Aluminum, ppm <1
Chromium, ppm <1
Iron, ppm 1
Nickel, ppm <1
Lead, ppm <1
Antimony, ppm <1
Tin, ppm <1
  1. Standards, shown in yellow are established by API, SAE and others.
  2. Test Method for metal analysis is ASTM D5185.
  3. This specification is expressed to two significant figures, therefore results up to 15.5 are considered on specification.