My oil is low between changes. Is that normal?

Drive in today

General guidance for this symptom. A warning light that is flashing or an overheating engine: stop driving and call.

Likely causes

• Normal consumption past the rings

  Every engine burns some oil. Turbocharged and direct-injection engines, and small engines that rev high at 4,500 feet, tend to use more. Check your owner's manual; several makers print an acceptable consumption figure. Keep the level at the full mark with the grade on the cap and shorten the interval if the manual's severe-service schedule applies to you.

  Full-service oil change
• A long interval

  The AAA guidance that many modern engines on synthetic go 5,000 to 7,500 miles is for normal conditions. Mountain driving, towing, dust and extreme heat and cold are all severe conditions in most manuals, and all four describe a normal year in Northern Nevada. A shorter interval means the oil is replaced before consumption has a chance to run the level low.

  Full synthetic oil change
• An external leak you have not seen

  A seep at the valve cover, filter or pan can lose a quart over a few thousand miles without a puddle, because it burns off the exhaust or blows back along the underside. We look for it on the lift at every service.

  Multi-point maintenance check
• A clogged PCV valve

  The positive crankcase ventilation valve lets blow-by gases out of the crankcase. When it sticks, pressure builds and oil gets pushed past seals and into the intake. It is a small part and a common cause of sudden consumption on an engine that was fine last year. We can tell you where it is and whether it looks gummed; replacement is a repair-shop item on most engines.

  Multi-point maintenance check
• Worn valve seals or rings

  The mechanical reasons. Blue smoke at start-up points at seals; smoke under hard acceleration points at rings. A high-mileage oil can reduce the loss on an older engine. A compression test at a repair shop settles it.

  High-mileage oil change

People are often surprised that an engine can be fine and still use oil. Piston rings seal, but not perfectly, and a thin film is supposed to stay on the cylinder wall and burn. Add a long interval, a hot summer and a few trips over Spooner Summit with the engine working hard, and a quart can disappear without a drop on the driveway. The question is not whether the level moved. It is how fast, and whether it is getting faster. Here is how we help you answer that in the bay, and what to do about it.

How to measure it instead of guessing

1. At your next oil change, note the mileage on the sticker. The level starts at full.
2. Check the dipstick on level ground, engine off for several minutes, every two weeks or every other fuel stop. The Car Care Council suggests a monthly check as the minimum.
3. Write down the mileage the first time the level reaches the low mark. On most dipsticks the distance between the marks is about one quart.
4. Divide the miles by the quarts. Four thousand miles per quart on a 120,000-mile engine is unremarkable. One thousand miles per quart is a problem to chase.

Bring the number to any of our service centers. It tells us more than a photo of the dipstick does.

What to top off with

The grade printed on your oil cap, in whatever type you can get. Mixing a conventional quart into synthetic for a top-off does not hurt anything; mixing grades, 10W-40 into a 0W-20 engine, is what to avoid. Keep a quart in the trunk. Our oil cap guide explains the numbers.

If you are adding more than a quart between changes, do not treat the top-off as the fix. Drive in. A full-service oil change gives us a known starting point, and the lift gives us a look at the leaks you cannot see from the driveway.

What we do, and what goes to a repair shop

We check the level and the condition of the oil, trace any external leak to its source, look at the PCV hose and the breather for oil pooling, note smoke at the tailpipe, and ask how fast the level has dropped. Leaks at the plug or filter we fix. If the manual allows a different grade for high mileage or hot climates, we talk it through and you choose. A high-mileage oil is a reasonable step on an engine past 75,000 miles with mild consumption.

We do not do compression tests, PCV valve replacement on buried engines, seals or rings. When the numbers point there, we say so and recommend a repair shop or the dealer, with your consumption figure written on the invoice so they do not have to start from zero.

Why it is worse here than the manual expects

• Thin air at 4,400 to 4,900 feet means more throttle for the same speed, and more throttle means more blow-by
• A 60-degree daily swing most of the year stresses seals
• Short commutes (Washoe County averages 22.5 minutes, Census ACS 2024) never fully warm the oil, so moisture and fuel dilute it
• Tahoe weekends and the Mount Rose grade run the engine hot and hard for an hour at a time