B10 & B50 Life of Diesel Engines

Diesel Engine B10 & B50 Life Explained

B10 and B50 life are the industry standard for measuring the life expectancy of an engine. Both are typically measured in miles of operation before an engine overhaul or replacement is required. Many people assume that B10 life means that at the given mileage, the engine will have worn 10%, and at B50 life the engine will have worn 50%. This is not the case, as B10 and B50 life use a statistical approach to approximating expected engine life. These figures are not typically advertised to the public for light duty diesels (3/4 and 1 ton pickups), but are generally published by manufacturers of medium and heavy duty engines. Of course, how an engine is used and maintained remains the primary defining factor in engine longevity.

B10 Engine Life

The expected engine life, measured in miles of operation, before 10 percent of all engines in operation will require major repair(s), overhaul, or replacement.

Example: The 7.3L Power Stroke has a B10 life of 200,000 miles. Therefore, 10 percent of all engines in operation can be expected to require an overhaul at/near 200,000 miles.

B50 Engine Life

The expected engine life, measured in miles of operation, before 50 percent of all engines in operation will require major repair(s), overhaul, or replacement.

Example: The 5.9L Cummins has a B50 life of 350,000 miles. Therefore, half of the engines in operation can be expected to require an overhaul at/near 350,000 miles.

An "overhaul" or "major repair" is considered a repair that requires removal of the cylinder heads or dropping of the oil pan. Failure/replacement of components that are accessible without removing the heads or dropping the oil pan do not attribute to B10/B50 life expectancy measurements.

B10 & B50 life are statistical measurements of engine life. As such, they don't represent a definite time when your engine will require a repair or overhaul. Proper maintenance and care will ensure that you get the most from your engine. Following the OEM maintenance recommendations will help ensure that your engine meets of exceeds the manufacturers life expectancy.