Piston Slap: Acceptable Oil Consumption?

Sajeev Mehta
by Sajeev Mehta

Justin writes:

Sajeev,

First I wanted to let you know that nearly everyday on my lunch break I check TTAC and each time I see a Piston Slap article I always make sure to read through it. I admire your knowledge and have learned quite a bit from your articles. I guess that I have a two part question.

The first part being since when has it become “acceptable” that a modern (low mileage) engine can consume a quart of oil in less than 5K miles. Audi and VW jump the front on my mind with their 2.0T mills, but I hear more and more through the woodwork about engines drinking oil. The second part of my question probably has more to do with correlation than causation but it seems like direct injection plays a role in this IMO unacceptable oil consumption.

Thanks!

Sajeev answers:

Why thank you for your kind words! This series is a shared duty between you the reader, me the writer and The Best and Brightest’s comments. We got a sweet little gig here, ya know? On to your queries…

I think one could write a PhD thesis on acceptable oil consumption, as it affects damn near every manufacturer these days. Yeah, blaming Audi and VW for that is a bit disingenuous. The V-10 powered BMW M-series burned rotary Mazda-levels of oil from day one. And cheaper, mainstream Japanese and American brands are far from exempt.

Like this thread suggests, I reckon acceptable oil consumption stems from two things: piston ring design (low tension?) and lightweight (like 5w-20) oils. Think about how many modern mills effortlessly zing the rev counter well past 6000 RPM and last for years with great horsepower figures AND fantastic fuel economy. Perhaps the downside to living in this new Golden Age of Automotive Engineering is a fraction of a quart of oil burning between service intervals.

I’m not saying its right or wrong, as I don’t know the right engine design and oil weight to end acceptable oil consumption while keeping today’s level of performance and long-term durability. And that’s where the B&B comes in. Off to you!

Send your queries to sajeev@thetruthaboutcars.com. Spare no details and ask for a speedy resolution if you’re in a hurry…but be realistic, and use your make/model specific forums instead of TTAC for more timely advice.

Sajeev Mehta
Sajeev Mehta

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  • -Nate -Nate on Oct 11, 2014

    Pretty good thread here ; I had no idea modern engines used so little oil . -Nate

  • Chaparral Chaparral on Oct 12, 2014

    A car that gets 40 MPG equipped with a two-stroke engine that burns gasoline and oil at a ratio of 50:1, will burn a gallon of oil every 2000 miles. That's 500 miles/quart. If you're doing worse than this with a four-stroke, I think you've got a problem.

    • -Nate -Nate on Oct 13, 2014

      So then ; You think maybe it's time to look at the piston rings in my old '69 C/10 shop truck ? . It _used_to oil foul the spark plugs every 150 ~ 200 miles but I up graded it to GM DELCO HEI ignition and opened the plug gaps to .075" and it now runs great and only has a *tiny* haze behind it although you can smell burned oil several miles behind it...... Is this not an O.K. situation ? . It hardly leaks a drop . -Nate

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