Ask Motor Maven: Shop Stories | September 25, 2019

Shop Stories: The case of the missing oil

A customer rolls onto our service lane with a loud, tinny/clunky noise from the engine. It’s not necessarily what all of us here would consider a DOA-like noise, but it is an unhealthy enough sound that it raises concern, while also indicative of problems to come.

This customer, happened to be a regular customer, whom had visited our dealership quite a few times over the course of the last year for more frequent-than-normal oil change appointments, in addition to several top-offs of the vehicle’s oil in-between appointments. And more frequent in this case meant sooner than the 5000 miles/6 months/less than 30% oil life remaining.

When asked regarding the issue, the customer had shared it was quite normal to have the frequent appointments, as well as the top-offs, and had noticed that after every visit, the engine would run (and sound) significantly better. 

Another fact to add to this story, there was also no sign of oil leaking or spots under the vehicle. At this customer’s most recent visit, the engine contained only half the oil required to operate without compromising anything, which had it been leaking, it would have left significantly noticeable puddles.

Now, what the customer did not know, was the low oil wasn’t normal. In fact, your engine should not really be losing that much oil (small discrepancies are ok). [Much] older vehicles have had tendencies at times to burn oil, but losing over a quart or more of oil in-between maintenance appointments can be a sign there is a larger problem at hand. 

In the customer’s defense, those outside of the automotive industry may not know how oil works, and understand it is to be a constant lubricant, not a fluid to be used up and refilled like your gas tank (which as a reminder, gas is a combustible liquid and is “burned” away in use).

So, in this and every case regarding oil in your engine, there is a certain amount of oil required to have the engine run properly. This vital fossil-derived liquid not only lubricates the delicate parts that create and keep up the engine’s power, but it also in turn cleans the engine. The reason for oil changes is really to remove the used, dirty liquid, and replace it with new oil to keep everything lubricated and clean.

For a more visual explanation of this action, check out Automotive Basic’s YouTube video on “How Engine Lubrication System Works.”

Without your regular intervals of oil changes (5000/6/30 rule mentioned above), it continues to lubricate and collect dirt until it forms a sludge built up more of collected contaminates rather than lubricating oil, which will not work itself through the engine. This can (and will) cause damage to the engine, with potentially leading to seize it, rendering your vehicle completely immobile and well, if it is one of your only vehicles, that can be quite problematic.

While this isn’t an every-case system, it’s always good practice to check your oil level, which GM indicates checking your oil at every fuel stop, as well as checking the area where you’ve parked for any fluids other than the condensation that may have dropped from your condenser for your AC system.

This is oil removed from an engine that was clearly not changed regularly. The bottom layer is sediment…

And to end, a photo of a sample of oil pulled from an engine and all the sediment/dirt having separated from the oil in layers. This particular collection is utilized in a high school shop class as an example of what can happen to oil if not changed regularly. Now, it is certainly not the worst oil mix that has come out of an engine, but it’s an example of what can be fed through an engine, and well, it probably isn’t doing much lubricating at all.


“For the Miles Ahead” is the DeNooyer Chevrolet blog series dedicated to demystifying automotive maintenance and service needs for the friends, family and customers of DeNooyer. If you have a question about service maintenance or car-related troubles, write to Motor Maven at MotorMaven@denooyer.com, and it could be included in the next publishing of “Ask Motor Maven.”


*Edits made on 9/26 to add GM guide is to check your oil level during every fuel stop.

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