# Really necessary to check oil level on car? **URL:** \ **Category:** Factual Questions\ **Created:** [October 21, 2010, 7:14pm UTC](https://boards.straightdope.com/t/really-necessary-to-check-oil-level-on-car/557919 "2010-10-21T19:14:19Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![control-z](https://avatars.discourse-cdn.com/v4/letter/c/eada6e/32.png) [@control-z](https://boards.straightdope.com/u/control-z)\ **Post date:** [October 22, 2010, 12:03am UTC](https://boards.straightdope.com/t/really-necessary-to-check-oil-level-on-car/557919/21 "2010-10-22T00:03:32Z")
> [@rachelellogram](#): > > My car has an “oil life” gauge (from 100 to 0%). If the oil was leaking out or something, wouldn’t the gauge indicate that by going down too quickly? I think those oil life gauges are an optical gauge that measures how dirty the oil is. Not sure what it would do with no oil to measure. ---
**Author:** ![Absolute](https://avatars.discourse-cdn.com/v4/letter/a/b2d939/32.png) [@Absolute](https://boards.straightdope.com/u/Absolute)\ **Post date:** [October 22, 2010, 12:03am UTC](https://boards.straightdope.com/t/really-necessary-to-check-oil-level-on-car/557919/22 "2010-10-22T00:03:35Z")
> [@rachelellogram](#): > > My car has an “oil life” gauge (from 100 to 0%). If the oil was leaking out or something, wouldn’t the gauge indicate that by going down too quickly? No. The oil life computers used by car manufacturers can take a few forms: 1. Mileage since last oil change (the simplest and least useful). 2. Gallons of fuel burned since last oil change. 3. Sensors in the oil that measure conductivity and other properties to determine when it has too many contaminants. Your car is likely to have #3. It is unlikely to reflect a low oil level, as most cars will begin to experience damaging low oil pressures when the oil level drops to about 80% of the full level. There is still a large volume of oil in the system at that point, and unless you continued to drive in that state for thousands more miles, the quality of the remaining oil would not be noticeably worse. The oil life gauge _would_ decrease faster than normal as your engine tears itself apart and debris is left in the oil, but you certainly don’t want to rely on that process to tell you when to add more oil. ---
**Author:** ![Gary\_T](https://avatars.discourse-cdn.com/v4/letter/g/3ec8ea/32.png) [@Gary\_T](https://boards.straightdope.com/u/Gary_T)\ **Post date:** [October 22, 2010, 3:16am UTC](https://boards.straightdope.com/t/really-necessary-to-check-oil-level-on-car/557919/23 "2010-10-22T03:16:35Z")
> [@rachelellogram](#): > > My car has an “oil life” gauge (from 100 to 0%). If the oil was leaking out or something, wouldn’t the gauge indicate that by going down too quickly? The oil life meter advises on the _quality_ of the oil. In no way does it advise on the _quantity_ of oil. ---
**Author:** ![Wheeljack](https://avatars.discourse-cdn.com/v4/letter/w/838e76/32.png) [@Wheeljack](https://boards.straightdope.com/u/Wheeljack)\ **Post date:** [October 22, 2010, 9:41am UTC](https://boards.straightdope.com/t/really-necessary-to-check-oil-level-on-car/557919/24 "2010-10-22T09:41:19Z")
> [@Balthisar](#): > > Doesn’t the Prius have an oil level sensor? I thought pretty much all newish cars had them. I haven’t checked my oil in years and years. I think it’s a bad idea to rely on this kind of technology to eliminate basic maintenance tasks. I’ve had to change the oil pressure sensors and the coolant temp sensors on all three of my cars at least once; it’s a pretty common failure as they get older. I’m just not wild on trusting a ten dollar sensor to protect a $2000 engine when a visual check is so easy. YYMV. 😃 ---
**Author:** ![Raguleader](https://avatars.discourse-cdn.com/v4/letter/r/258eb7/32.png) [@Raguleader](https://boards.straightdope.com/u/Raguleader)\ **Post date:** [October 22, 2010, 10:09am UTC](https://boards.straightdope.com/t/really-necessary-to-check-oil-level-on-car/557919/25 "2010-10-22T10:09:59Z")
Others have said it as well, but I’d still like to toss my two cents in: You don’t have to check your oil, ever. If you really want to have a brand new car that much sooner. 😃 On my 2001 Pontiac Grand Am, the manual said to check the oil after every refueling. Probably because if there is a convenient place to find out you’re a quart low, it’s at a gas station. ---
**Author:** ![Thudlow\_Boink](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/thudlow_boink/32/320_2.png) [@Thudlow\_Boink](https://boards.straightdope.com/u/Thudlow_Boink)\ **Post date:** [October 22, 2010, 12:16pm UTC](https://boards.straightdope.com/t/really-necessary-to-check-oil-level-on-car/557919/26 "2010-10-22T12:16:49Z")
Okay, question: If cars can have sensors, gauges, or idiot lights to tell you when other things are running low (like gasoline or tire pressure), and even now an oil quality indicator, why not one for when the oil is low? ---
**Author:** ![bouv](https://avatars.discourse-cdn.com/v4/letter/b/bc8723/32.png) [@bouv](https://boards.straightdope.com/u/bouv)\ **Post date:** [October 22, 2010, 12:45pm UTC](https://boards.straightdope.com/t/really-necessary-to-check-oil-level-on-car/557919/27 "2010-10-22T12:45:42Z")
> [@Thudlow\_Boink](#): > > Okay, question: If cars can have sensors, gauges, or idiot lights to tell you when other things are running low (like gasoline or tire pressure), and even now an oil quality indicator, why not one for when the oil is low? They do, although it’s not so much an “oil level” sensor as an “oil pressure” sensor. However, I would say that in most cases, if the oil pressure light goes off, or the oil pressure gauge gets low, it’s because of low oil. At any rate, if it does go off, the first thing you sohuld do is pull over and check thr oil. If it’s at a god level, then you know something else is causing low oil pressure. ---
**Author:** ![Balthisar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/balthisar/32/2825_2.png) [@Balthisar](https://boards.straightdope.com/u/Balthisar)\ **Post date:** [October 22, 2010, 12:59pm UTC](https://boards.straightdope.com/t/really-necessary-to-check-oil-level-on-car/557919/28 "2010-10-22T12:59:02Z")
> [@bouv](#): > > They do, although it’s not so much an “oil level” sensor as an “oil pressure” sensor. However, I would say that in most cases, if the oil pressure light goes off, or the oil pressure gauge gets low, it’s because of low oil. At any rate, if it does go off, the first thing you sohuld do is pull over and check thr oil. If it’s at a god level, then you know something else is causing low oil pressure. Cars have always had oil pressure sensors, sometimes linked to analogue gauges on the instrument panel. Oil level sensors actually indicate low oil level. You can still have proper pressure with low oil, but depending on where your oil’s going, maybe not for long. ---
**Author:** ![Gary\_T](https://avatars.discourse-cdn.com/v4/letter/g/3ec8ea/32.png) [@Gary\_T](https://boards.straightdope.com/u/Gary_T)\ **Post date:** [October 22, 2010, 1:18pm UTC](https://boards.straightdope.com/t/really-necessary-to-check-oil-level-on-car/557919/29 "2010-10-22T13:18:40Z")
> [@Thudlow\_Boink](#): > > Okay, question: If cars can have sensors, gauges, or idiot lights to tell you when other things are running low (like gasoline or tire pressure), and even now an oil quality indicator, why not one for when the oil is low? > [@bouv](#): > > They do, although it’s not so much an “oil level” sensor as an “oil pressure” sensor. However, I would say that in most cases, if the oil pressure light goes off, or the oil pressure gauge gets low, it’s because of low oil. At any rate, if it does go off, the first thing you sohuld do is pull over and check thr oil. If it’s at a god level, then you know something else is causing low oil pressure. No, this is apples and oranges. There are oil pressure senders (also called switches or sending units, but not sensors) and every car has one to operate either a pressure gauge or a warning light. Then there are oil level sensors in some (but not most) cars which operate a warning light. Pressure indication is necessary because it’s a critical function and there’s no easy way to tell otherwise if the pressure is low. Level indication is a fluff feature because it’s quite easy to check the level with the dipstick. It is true that most of the time low oil pressure is due to low oil level, but as mentioned is not true in all cases. Sometimes the pressure is low due to a mechanical problem such as a faulty oil pump. It’s not uncommon for drivers to see an indication of low pressure, check the oil level to find it’s okay, and continue to drive. If they’re lucky, it’s a faulty pressure sender and the pressure is good; if they’re not so lucky the pressure really is low and their engine is self-destructing as they drive. ---
**Author:** ![don\_t\_ask](https://avatars.discourse-cdn.com/v4/letter/d/e68b1a/32.png) [@don\_t\_ask](https://boards.straightdope.com/u/don_t_ask)\ **Post date:** [October 22, 2010, 1:18pm UTC](https://boards.straightdope.com/t/really-necessary-to-check-oil-level-on-car/557919/30 "2010-10-22T13:18:46Z")
Once I was driving on the highway, heading south, and the oil pressure light came on. Luckily there was a garage over the next hill. I pulled in and poured oil into the motor and it poured straight out onto the cement. A mechanic came and explained that once the oil pressure light came on I had already fucked the motor due to low oil. Turned out he wasn’t lying. I left the car with him, went where I was going and picked up the repaired car a few days later on the way home. A few years later, heading north, south of the same town, in a different car the same thing happened. Suddenly the oil pressure light came on. I had liters of oil in the boot and poured it in, pulled up at the next garage and fixed the problem. What was the problem? The oil pressure switch. The $5 part that tells you if your oil is low. It had fractured and was allowing the sump to pump dry. So the only 2 times I have ever been in oil trouble have been caused by the cheap part that tells me I am in oil trouble. If I had had no oil pressure switch and had simply screwed a bolt in to where it goes I never would have had a problem. ---
**Author:** ![Gary\_T](https://avatars.discourse-cdn.com/v4/letter/g/3ec8ea/32.png) [@Gary\_T](https://boards.straightdope.com/u/Gary_T)\ **Post date:** [October 22, 2010, 1:48pm UTC](https://boards.straightdope.com/t/really-necessary-to-check-oil-level-on-car/557919/31 "2010-10-22T13:48:51Z")
> [@don\_t\_ask](#): > > If I had had no oil pressure switch and had simply screwed a bolt in to where it goes I never would have had a problem. Okay, but in the other 99.99% of cases it’s a bigger problem to not have an oil pressure switch. ---
**Author:** ![pyromyte](https://avatars.discourse-cdn.com/v4/letter/p/d26b3c/32.png) [@pyromyte](https://boards.straightdope.com/u/pyromyte)\ **Post date:** [October 22, 2010, 2:04pm UTC](https://boards.straightdope.com/t/really-necessary-to-check-oil-level-on-car/557919/32 "2010-10-22T14:04:56Z")
> [@GreasyJack](#): > > I would actually disagree with this (that it’s less necessary on a newer car). Yes, you’re right, you bring up a good point. I guess I just meant that you can _probably_ get away with it, but if you’re wise, you wouldn’t try to get away with it. Some people just refuse to check it. My sister in-law for instance never checks anything! Nothing I say seems to make a difference. She has a Mazda 4-banger with about 100k miles on it and a heater hose started leaking ('cept she didn’t know it). She went on a long road trip and the temp light came on.. she kept driving until it stalled and wouldn’t restart. The aluminum head warped and allowed a piece of the head gasket to blow out.:smack: But please no one go opening their radiator cap at a gas station with a hot engine, check that in the driveway with a cold engine, or you could end up like a guy at my work with scars all over his hands/arms. Don’t trust the marks on the overflow tank either, because I once had a car that didn’t suck it back up as it cooled, instead it just sucked air. Looking at the tank, it appeared full, but the radiator/engine were about empty. > [@mnemosyne](#): > > Holding onto the handle to get the gas into the car? The auto-fill nozzle thingies have all been disabled here and all pumps require someone to actually squeeze the handle themselves. > [@Bad\_Astronaut](#): > > I have something more important to do - standing there holding the nozzle because the damn gas stations all removed the little latch that used to let you walk away while it filled. > /end of hijack I hate those gas pumps like that. My gas cap is the perfect size to jam in the handle. Works great for me, although I generally try to be back to the nozzle by the time I think its going to cut off (I’m pretty consistent with fueling, so when it gets to about 16 gallons, i know its time to be ready). Of all my years of driving and fueling cars, I have once had a nozzle that didn’t shut off and spewed gas all over, not exactly the safest of situations. ---
**Author:** ![don\_t\_ask](https://avatars.discourse-cdn.com/v4/letter/d/e68b1a/32.png) [@don\_t\_ask](https://boards.straightdope.com/u/don_t_ask)\ **Post date:** [October 22, 2010, 2:45pm UTC](https://boards.straightdope.com/t/really-necessary-to-check-oil-level-on-car/557919/33 "2010-10-22T14:45:50Z")
> [@Gary\_T](#): > > Okay, but in the other 99.99% of cases it’s a bigger problem to not have an oil pressure switch. Well maybe, but they are the only times my oil pressure light have ever come on while driving. So there is no other 99.99% of cases. There are 2 and in 100% of them the problem was the oil pressure switch. Mind you, that’s only 40 years of driving, so maybe in the future I will have an oil light come on 19,998 times when it is not a failed oil pressure switch and you will be proved correct, ---
**Author:** ![Gary\_T](https://avatars.discourse-cdn.com/v4/letter/g/3ec8ea/32.png) [@Gary\_T](https://boards.straightdope.com/u/Gary_T)\ **Post date:** [October 22, 2010, 3:32pm UTC](https://boards.straightdope.com/t/really-necessary-to-check-oil-level-on-car/557919/34 "2010-10-22T15:32:15Z")
> [@don\_t\_ask](#): > > Well maybe, but they are the only times my oil pressure light have ever come on while driving. So there is no other 99.99% of cases. There are 2 and in 100% of them the problem was the oil pressure switch. Mind you, that’s only 40 years of driving, so maybe in the future I will have an oil light come on 19,998 times when it is not a failed oil pressure switch and you will be proved correct, For crying out loud, I’m not talking about **YOUR** personal experience, I’m talking about all the other cars on the road. It’s already been “proven correct” that oil lights come on for reasons other than a faulty sender, and sometimes the reason is that the oil pressure is low. I’d hate to see someone ruin an engine because they thought it was a good idea to replace an oil sender with a bolt. ---
**Author:** ![Dallas\_Jones](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dallas_jones/32/3277_2.png) [@Dallas\_Jones](https://boards.straightdope.com/u/Dallas_Jones)\ **Post date:** [October 22, 2010, 5:34pm UTC](https://boards.straightdope.com/t/really-necessary-to-check-oil-level-on-car/557919/35 "2010-10-22T17:34:27Z")
> [@Thudlow\_Boink](#): > > Okay, question: If cars can have sensors, gauges, or idiot lights to tell you when other things are running low (like gasoline or tire pressure), and even now an oil quality indicator, why not one for when the oil is low? Let’s clear up a common misconception with the ‘oil quality indicators’ and ‘oil life remaining’ gauges. **No qualitative analysis of the oil is being done by these sensors.** An algorithm is being used to attempt to calculate when your oil needs changing. The program takes into account the mileage passed since last oil change, peak engine temperatures, amount of fuel used, number of engine start cycles, high RPMs reached, etc. These algorithms are becoming very sophisticated, but it is still predictive maintenance, not analysis. If you think that your car is performing some kind of qualitative tests on your oil you are mistaken. ---
**Author:** ![Musicat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/musicat/32/20189_2.png) [@Musicat](https://boards.straightdope.com/u/Musicat)\ **Post date:** [October 22, 2010, 5:39pm UTC](https://boards.straightdope.com/t/really-necessary-to-check-oil-level-on-car/557919/36 "2010-10-22T17:39:57Z")
> [@bouv](#): > > If it’s at a god level, then you know something else is causing low oil pressure. The Devil? ---
**Author:** ![Absolute](https://avatars.discourse-cdn.com/v4/letter/a/b2d939/32.png) [@Absolute](https://boards.straightdope.com/u/Absolute)\ **Post date:** [October 22, 2010, 6:02pm UTC](https://boards.straightdope.com/t/really-necessary-to-check-oil-level-on-car/557919/37 "2010-10-22T18:02:00Z")
> [@Dallas\_Jones](#): > > Let’s clear up a common misconception with the ‘oil quality indicators’ and ‘oil life remaining’ gauges. > > **No qualitative analysis of the oil is being done by these sensors.** > > An algorithm is being used to attempt to calculate when your oil needs changing. The program takes into account the mileage passed since last oil change, peak engine temperatures, amount of fuel used, number of engine start cycles, high RPMs reached, etc. > > These algorithms are becoming very sophisticated, but it is still predictive maintenance, not analysis. > > If you think that your car is performing some kind of qualitative tests on your oil you are mistaken. You are the one who is mistaken. Many cars (e.g. BMW, Mercedes) use a sensor that performs actual measurements on the oil, and these measurements are fed into the oil change interval algorithm. Here is just one company that makes these: [http://www.gillsensors.co.uk/content/oil\_condition\_sensors.html](http://www.gillsensors.co.uk/content/oil_condition_sensors.html) ---
**Author:** ![Dallas\_Jones](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dallas_jones/32/3277_2.png) [@Dallas\_Jones](https://boards.straightdope.com/u/Dallas_Jones)\ **Post date:** [October 22, 2010, 6:33pm UTC](https://boards.straightdope.com/t/really-necessary-to-check-oil-level-on-car/557919/38 "2010-10-22T18:33:00Z")
> [@Absolute](#): > > You are the one who is mistaken. Many cars (e.g. BMW, Mercedes) use a sensor that performs actual measurements on the oil, and these measurements are fed into the oil change interval algorithm. > > Here is just one company that makes these: > > [http://www.gillsensors.co.uk/content/oil\_condition\_sensors.html](http://www.gillsensors.co.uk/content/oil_condition_sensors.html) Oh good! Another car guy, thank you. And I am not being snarky. I will admit my error. Some qualitative analysis is being done by the sensors and then used by the algorithm/program to try to predict when the oil should be changed. ---
**Author:** ![Galileo](https://avatars.discourse-cdn.com/v4/letter/g/85e7bf/32.png) [@Galileo](https://boards.straightdope.com/u/Galileo)\ **Post date:** [October 22, 2010, 7:32pm UTC](https://boards.straightdope.com/t/really-necessary-to-check-oil-level-on-car/557919/39 "2010-10-22T19:32:42Z")
Okay, so far the message is loud and clear: Check your car’s oil level because you should, and because it’s quick and easy. I agree with the quick and easy, but I’m still not clear on the “should”. My situation: 1. New car 2. In four years, I’ll be trading it in. 3. I travel about 14,000 km per year (less than 9,000 miles). 4. Regularly scheduled oil changes and inspections will be done at the dealer. (Included in 4-year warranty.) 5. Car has a variety of sensors and warning lights. Let’s say I decide that I’m never going to check the oil level. Would someone please lay out a sequence of events that would cause engine damage and explain how that damage could be prevented by checking the oil level every week, rather than merely relying on the car’s warnings? ---
**Author:** ![Gary\_T](https://avatars.discourse-cdn.com/v4/letter/g/3ec8ea/32.png) [@Gary\_T](https://boards.straightdope.com/u/Gary_T)\ **Post date:** [October 22, 2010, 7:40pm UTC](https://boards.straightdope.com/t/really-necessary-to-check-oil-level-on-car/557919/40 "2010-10-22T19:40:46Z")
> [@Galileo](#): > > Let’s say I decide that I’m never going to check the oil level. Would someone please lay out a sequence of events that would cause engine damage and explain how that damage could be prevented by checking the oil level every week, rather than merely relying on the car’s warnings? Unbeknownst to you, a significant oil leak develops (faulty gasket or seal, faulty oil sender, rock hits oil pan, etc.). Oil pressure sender fails electrically. The first thing that alerts you to being low on oil is a rod knocking. [Previous page](https://boards.straightdope.com/t/really-necessary-to-check-oil-level-on-car/557919.md?page=1) [Next page](https://boards.straightdope.com/t/really-necessary-to-check-oil-level-on-car/557919.md?page=3)