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Oil use gauge

This is my first car with a gauge indicating remaining use of oil since last change. It reads 62 now. Car is used nearly
in city driving–seldom go on highway.
Can I trust gauge to indicate when to change oil? Or change at say 3, 4, or 6 months?

Most modern cars will tell you when to change the oil. My BMW 328i has a bar graph that slowly goes from green to yellow to red. It’s not just based on mileage, but cold starts, how it’s driven and several other inputs. Cold starts are much harder on cars than highway miles or time. Read your owner’s manual for more info.

The oil life monitor system seems to be fairly trustworthy. GM has been using it for around 20 years now with good luck. Do bear in mind, though, that this only monitors when the algorithm says you should change your oil and has nothing to do with the need to periodically open the hood and check the dipstick and maintain the oil level. This is an absolute necessity unless your idea of a good time is shelling out a few thousand dollars to have your engine replaced because it ran out of oil. I only mention this because it is a very common topic of discussion on here and nobody needs to go through that lesson the hard way (although many, many people do).

I don’t like oil life monitors. I ignore mine and never go past 5000 miles or 6 months. (I always hit 5000 miles long before). But this issue has been discussed many many times and many are happy to trust them. On the right side of the screen about midway down - mostly hidden - is a Search box with which you can search this forum for one of the many discussions about these automated systems.

Let me emphasize, as mark9207 noted - that system doesn’t actually know a thing about your actual oil. It doesn’t know the oil level or anything else. It just “knows” all sorts of things about what the engine has been doing since the monitor was last reset. The oil condition is an inference based on that - but doesn’t include oil level or any measurements from the actual oil in your crankcase. You could reset the monitor without changing the oil and it wouldn’t know the difference. Use your dipstick at least every other gas fill up, and especially after the oil is changed.

I Change Oil Using Full-Synthetic, Every Five Thousand Miles, Whenever Any Of Our Family Cars’ Odometers End In 5000 Or 0000 (Example: 15,000 Or 30,000,) And I Do It Myself.

I keep up on oil changing and checking.
That way I don’t have to look anything up to know when it’s due on each of 7 cars. My wife’s OLM ususually indicates from 35% to 40% life remaining at each change. I err on the side of caution. Oil is cheap and life is full of uncertainties. My oil changes are certain. Still, I log all maintenance and repairs in a “logbook” spiral note pad in each car’s glove compartment.

I Keep it simple.
Every single week-end, without fail, when the cars are parked and engines “cold” I take the few minutes needed to check the cars’ fluid levels and inspect under the hood and top-off windshield washer fluid. The oil dipstick need not even come out all the way. Transmission fluid and tires are checked monthly, but they still are eye-balled for any possible leaks.


You should not rely on these things to tell you when to change the oil nor should you rely on it to tell you if the oil level is low.

Many people who rely on these things end up trashed engines. A good example of this would be the discussion on this forum about 6 months ago involving a 2009 Chevy Traverse with 40k miles and a wiped engine.

The problem I think with oil life monitors is that when your OLM says you have 40% remaining on the oil, I just can’t imagine that the oil is still protecting your engine as well as when you’re at 100% It may still be adequate, or maybe not. The system can’t take into account how full the crankcase is, what grade and quality of oil you’ve put in, etc. These might be great for people that need something to shout at them to get their oil changed, but I’d rather do a little better myself and leave some margin for prudence. Of course I normally fill up my gas tank when it gets down to 1/4 tank instead of letting it run dry too.

If you’re going to rely on this, I wouldn’t let it go under 50% personally. Oil isn’t that expensive—do you really need to get every last bit of use out of it, possibly at the expense of your engine?

Some expensive cars actually monitor oil quality, by passing a current through the oil. The resistance tells the computer about the metal shavings & concentration of ion (acidity) in the oil

chunky_azian, another method uses IR light bounced off the interior surfaces of faceted crystal and into a photodetector. That crystal (CZ works really well as a cost effective solution) extendeds past the end of the sensor body and is immersed in the oil. When the light “bounces” off a facet, it actually extends slightly beyond the surface and into the liquid before re-entering the crystal. Therefore, each reflection results in a partial absorption of the light. The cumulative effect produces an absorption spectroscopy signal relative to the oil purity. This process of measurement is known as Attenuated Total Reflectance (ATR) and has been used for a long time to measure certain liquids and even solids. (Not meant to be a scientific discourse on the process but just to describe in simple terms!) Diesel engine oil monitoring is a great application for an ATR sensor as the particulate level is primarily used to determine change interval.

The crystal is less prone to the accumulation of contaminants that decrease the sensitivity and/or increase the zero offset of the sensor as happens more readily with the resistance based sensors. They are slightly more expensive to produce but have a good cost/benefit ratio due to their longevity.

Many people who rely on these things end up trashed engines. A good example of this would be the discussion on this forum about 6 months ago involving a 2009 Chevy Traverse with 40k miles and a wiped engine.

My problem with that example is it wasn’t a failure of the OLM that caused the problem, or a bad algorithm or anything else, it was a failure of the driver to understand what the OLM meant.

As mentioned on this thread, having an OLM does not relieve you of the need to actually check the oil level on the dipstick regularly. If you want reliable information, the best recommendation would be to send off an oil sample once the OLM says its time for a change. If the oil still measures within spec, then you’ll know its reliable and you can trust the OLM’s interval. Or you can go the cautious route and change the oil at 50% and send off a sample and see if you could go to 30% or whatever step

About that Traverse, and if I remember correctly, GM issued a TSB about reprogramming the ECM and the OLM because of inaccuracies.

I am in agreement that part of the problem was the owner of the car who never raised the hood to check the oil level. That’s yet another problem with these things; totally wash the idea of even caring if the engine has oil in it or not clean out of the mind.

As oil deteriorates its dielectric constant increases. If the oil is passed between two conducting plates the electrical capacitance of the device increases. It is this increase in capacitance that oil quality sensors of the future will probably measure.

Real-time oil quality monitoring set to enter automotive industry

Tan Delta - Oil Quality Sensor - YouTube

Regardless, I change my oil when the monitor is at about 50% which is 4-5000 mile intervals depending on the car. I’m not going beyond 5000 miles for an oil change.

Two schools of thought here.

Oil changes are cheap, engine replacements not so.

People who have trusted the oil life monitors have not had any engine trouble.

I’ve been using mine, which does not give percentage, only and idiot light, and I have 237k miles without any oil related problems.

Oil Change recommendations from the many who responded are great.

You folks are wonderful and thanks for taking the time to respond.

My sister’s Pontiac has an OLM that she completely ignores and thinks is stupid. She usually has me change the oil on it every 2,500 to 3,000 miles, and feels like she is killing her car if she hits so much as 3,200 miles between oil changes. I tell her it’s fine but she prefers to err on the safe side. Her OLM is usually around 65% when she brings me her car. Here’s the craziest part: she also checks her dipstick every other week or so, even though her car uses no measurable amount of oil between changes. She is also a female in her mid 20s who does not use either of those facts as an excuse not to tend to her car the way a responsible owner should.

The funny thing is that most of the people on this board will insist that you change your transmission oil much more frequently than the owners’ manual recommends, on the grounds that the long life cited in the manual is bogus, to make the car look low maintenance and to get you through the basic warranty period. But the same people will tell you to follow the oil life monitor, even though, under normal driving conditions, it will give you the owners’ manual interval of 7500 miles or even longer.

Oil change recommendations are like religion. If you really want to know what your oil life is, send a sample of used oil to one of the independent testing labs. They can tell you whether the viscosity and additives have any life left, and whether you have any contaminants that would signal unusual wear.

My OLM would normally give me around 7500 miles. I ignore it and change at 5000.