12/06/2026 8:38 am
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Automotive Q&A
Subaru FB25 loses oil with no floor spots and a faint smell after highway driving
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A 2015 Forester uses roughly half a quart over 2,000 miles. There is no blue smoke, plugs look even and the PCV valve operates normally. The lower splash shield is dry, but a burnt-oil smell appears after sustained highway speed. Old staining is visible near the cam-carrier seam.
What is the best way to distinguish external loss that burns off from true oil consumption?
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13/06/2026 6:38 am
Clean the engine and shield completely, establish a measured oil-level baseline and add an approved fluorescent dye if needed. Inspect the cam-carrier and timing-cover seams immediately after the driving condition that creates the odor, including surfaces above the exhaust. At the same time, document crankcase pressure and look for oil in the intake.
If fresh dye appears externally while the level falls, repair the leak before beginning a consumption test. A dry garage floor does not exclude oil that reaches a hot shield and evaporates.
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14/06/2026 9:51 am
Fresh dye appeared at the right cam-carrier seam and tracked onto the exhaust shield without reaching the floor. After resealing that area, the smell disappeared and the oil level remained on the baseline mark through the next 2,000 miles.