Why Are Modern Engines Burning Oil?

Summary

The video explains why some modern engines consume oil, especially as they age. It identifies three routes for oil loss:

• External leaks, such as those from the valve-cover gasket, oil pan, or rear crankshaft seal. These are often visible under the car.
• The PCV system, which routes combustion gases that pass the piston rings back into the intake. Oil mist can be carried along if the system does not separate it effectively.
• Oil passing the piston rings into the combustion chamber, the video’s main focus.

Why manufacturers use low-tension rings

The presenter argues that low-tension piston rings reduce friction between the rings and cylinder walls, helping improve engine efficiency, fuel economy, and emissions.

To demonstrate the difference, he compares a new GM piston with standard rings to the same piston fitted with lower-tension motorcycle rings. Using a fishing scale, he measures roughly 12 pounds of force with the standard rings versus 2–3 pounds with the lower-tension set. He notes that this is a rough demonstration, not a controlled scientific test.

The video also discusses a 2018 SAE study conducted in a Mahindra testing laboratory. In a motored short-block test, researchers reportedly reduced ring tension by 24%, lowered overall short-block friction by about 5%, and did not find increased blow-by or oil consumption. The presenter cautions that the test did not involve combustion, so it could not fully reproduce the gas pressure that helps seal the upper piston ring in a running engine.

The presenter estimates that the friction reduction translates into only about 0.1–0.3% overall fuel-economy improvement for a vehicle, but says small gains across multiple design changes can add up. He cites a slide attributed to GM and shown in an energy.gov presentation, which indicates that engine mechanical and pumping friction accounted for 37% of mechanical losses in the cited EPA test-cycle breakdown.

How oil-change intervals may contribute

The video links oil consumption to the combination of low-tension rings and extended oil-change intervals. Its explanation is that longer intervals can allow more deposits to form; with less ring tension, deposits may make rings more prone to sticking, reducing their ability to control oil.

The presenter recommends changing oil more frequently than long standard intervals, suggesting about 5,000 miles as a conservative interval for many cars. He says he personally would not run regular oil for 10,000 miles without oil-analysis data. These are personal recommendations, not universal specifications; the video does not provide a vehicle-specific service schedule.

Products and remedies mentioned

• Mobil 1 Restore & Protect: The presenter says he has used it and describes it as an oil intended to help clean deposits. He notes that it was relatively new at the time of recording and that opinions about it were mixed.
• Valvoline oils: Mentioned among oils marketed for deposit cleaning, but no specific product or test results are discussed.

The presenter emphasizes prevention through regular oil changes and says results from deposit-cleaning oils may vary with driving habits and maintenance history. He does not demonstrate that these products repair worn or damaged rings.

Main speakers and sources

• Repair Geek presenter: Narrates the explanation, piston-ring demonstration, and maintenance opinions.
• 2018 SAE study conducted in a Mahindra testing laboratory: Source for the short-block friction findings.
• GM information shown in an energy.gov presentation: Source cited for the vehicle mechanical-loss breakdown.
• Mobil 1 and Valvoline: Oil brands discussed as offering deposit-cleaning products.