Time to Change Oil?





Introduction: Time to Change Oil?

How do you know when it is time to change your engine oil? Maybe there is a sticker on your door that is visible when you open the door and crane your neck down to waist level. But, you still need to subtract the mileage figure on the sticker from the reading on your odometer. It can work, but it is not a great system.

Step 1: Use the Change Oil Light?

Modern automobiles have a Change Oil light on the instrument display. See the green box. It lights when it is allegedly time to change your oil. But, it is only a computer's guess that it is time to change your oil. Your engine's computer notices the amount of city driving you do in comparison to highway driving and guesses that your oil has reached a certain level of contamination from engine wear, water vapor in the crankcase, acids, and engine blow-by gasses. A truly accurate assessment of your oil's condition would require testing in a laboratory.

The Low Tire Pressure light next to the Change Oil light also does not really know if one tire is low. It makes a secondary measurement that is usually explained by low tire pressure. It compares the number of revolutions each tire makes. If a tire is low, it has a smaller effective diameter and must turn more times per minute to keep up with the fully inflated tire on the opposite side of the car. My Low Tire Pressure light has remained "on" since a mechanic worked on the braking system a couple of years ago.

Step 2: Your Odometer Display

The odometer on modern automobile speedometers is digital. In addition to the total number of miles you have traveled, it can also record the number of miles you have traveled on this trip. I do not use it for that. But, I do use it to keep an indicator of how many miles it has been since my last oil change.

The trip meter shows it has been 2270 miles since my last oil change. The manufacturer of my automobile suggests I change the oil every 7500 miles. When mechanics write about oil changes and engine life, they usually say it is better to change the engine oil around 3000 miles. That means I will try to change my oil in just a little over 700 more miles.

Step 3: Trip Reset/Display Button

Normally, my odometer shows the total number of miles my automobile has traveled. If I press the Trip Reset/Display button once quickly, the odometer display changes to the number of miles this trip, or since my last oil change. Every so often when I am driving I press the button to remind myself of how many more miles I will drive before it is time to change the engine oil and filter.

When I change the oil, one of the last things I do is to press and hold the Trip Reset/Display button. This sets it back to zero. I also try to follow the procedure for making the Change Oil light shut off, if it is on.

Step 4: A Paper Record

I also keep a small notebook in the glove compartment. In it I write the date I changed my oil, the miles on the odometer, and anything else I did or changed. The trip meter alone would help me to change my oil at the desired intervals. The paper record will be helpful when I want to sell the car and a buyer wants to know what regular maintenance I have done.

I still need to remember to look at the miles on my trip meter to make certain I change my oil, but using it to keep a record of miles driven since the last oil change makes it far easier for me to remember.



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    I have a year 2006 Toyota truck with a V 6 engine and the manual recommends a service interval of approx 6000 miles before service is necessary. If you read the manual fine print it states that this is under ideal driving conditions- little or no stop and go driving or short trips. Many vehicles do not lead this kind of life. I try to use a rule that the oil and filter should be changed at 5000 miles or 5 months in my driving cycles . The Toyota scheme uses a simple reset arrangement using the trip odometer button to turn off the warning light that can be done by the owner. The service interval light appears to be triggered by a combination of time and mileage and it has nothing to do with the oil level as far as I can tell. A low oil level or low oil pressure is a different circuit as I understand the circuit. Having never had a low oil pressure or low oil level I cannot attest to this but believe I am correct.

    I usually change mine every 3000 miles. and add oil after about 1000 or so miles of driving.

    The oil light is a level indicator - it means there is too little oil to protect the engine properly.

    And if you drive around without topping up the oil, there is a loud bang and a piece of your engine the size of your fist goes through the radiator, punches off the front grill and renders you subject to sarcasm from roadside assistance personnel...

    . All the oil lights I've seen work off of pressure. It will still light up if the sump is full and the pump fails.

    Ah, things must have changed since last I read the manual for a car (a period measured in decades).

    There was a time when cars would have an oil pressure gauge I believe. And you checked the level with the dipstick. and changed the oil to suit the seasons


    . BTW, I was talking about the "Oil" (or "Check Oil") light. I wasn't at all clear, was I? :(