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Burning oil smell and low oil level on 2017 Highlander V6 (85k miles)

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Mike T. · rep 0 · May 25, 1:25 AM · 1 replies · solved · Question

Vehicle: 2017 Toyota Highlander Limited

Hi all,

I own a 2017 Toyota Highlander Limited with the 3.5L V6 engine, and it just hit about 85,000 miles. Lately, I've been noticing a distinct burning oil smell, especially after driving for a while or when the engine is hot. I checked the oil level, and it was quite a bit lower than it should be, even though I'm not due for an oil change yet.

I don't see any obvious puddles under the car, but the smell is definitely concerning. Could this be a common issue with these V6 engines at this mileage? What parts should I be looking at for potential leaks or excessive oil consumption? I'm worried about potential engine damage.

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 1:25 AM

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ClearTheCode admin answer:

A burning oil smell and low oil level on your 2017 Toyota Highlander with the 3.5L V6 at 85,000 miles are clear indicators of an oil leak or excessive oil consumption. Even without puddles, oil can burn off on hot engine components. Here are the most common culprits for this generation of Toyota V6 engines:

Common Causes for Burning Oil Smell and Low Oil:

  1. Valve Cover Gasket Leaks:

    • Cause: Over time, the rubber valve cover gaskets can harden and crack, leading to oil seeping out. On V6 engines, oil often drips onto the hot exhaust manifolds, causing a burning smell.
    • Action: Inspect the perimeter of both valve covers for signs of oil residue or wetness. This is a very common leak point.

  2. PCV (Positive Crankcase Ventilation) Valve Issues:

    • Cause: A clogged or faulty PCV valve can lead to increased crankcase pressure, forcing oil past seals and gaskets, or causing oil to be drawn into the intake manifold and burned.
    • Action: The PCV valve is relatively inexpensive and easy to replace. It's a good maintenance item to check.

  3. Oil Cooler Line Leaks:

    • Cause: Some Toyota V6 engines, especially earlier models, had issues with the rubber sections of the oil cooler lines degrading and leaking. While more prevalent in earlier 3.5L engines, it's worth checking.
    • Action: Inspect the oil cooler lines, typically found near the oil filter housing, for cracks or leaks.

  4. Oil Filter Housing Leak:

    • Cause: The plastic oil filter housing and its O-rings can sometimes develop leaks, especially after oil changes if not properly torqued or if the O-rings are damaged.

  5. Front Timing Cover Gasket Leak:

    • Cause: This is a more involved repair but can occur. Oil can weep from the timing cover gasket and drip down the front of the engine.

  6. Excessive Oil Consumption (Internal):

    • Cause: While less likely to produce a strong burning smell if it's purely internal, worn piston rings or valve stem seals can lead to oil being burned in the combustion chambers. This usually results in blue smoke from the exhaust, especially on startup or deceleration.

Recommended Steps:

  1. Visual Inspection: Carefully inspect the top, sides, and bottom of the engine with a flashlight, looking for fresh oil stains, wet spots, or drips. Pay close attention to the valve covers, oil filter area, and around the exhaust manifolds.
  2. Clean Engine: If you can, clean off any existing oil residue with an engine degreaser. Drive for a bit, then re-inspect to pinpoint the fresh leak.

When to See a Shop:

  • Soon: Any persistent oil leak needs to be addressed to prevent potential engine damage due to low oil levels.
  • If you cannot identify the source of the leak yourself.
  • If the oil level continues to drop rapidly after topping it off.
  • A professional can use UV dye in the oil to precisely locate elusive leaks.
  • No specific OBD codes are typically associated with external oil leaks, but low oil pressure could trigger a light if the level gets critically low.
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