why do you have to change your oil every 3 months?

Question

its 6,000,000 years old
why will it go bad in 3 mo.

you people either have no sense of humor or you just take yourselves too serious

Answer 1

All right Old Dude, you're a funny one alright. heh heh

Answer 2

Basically, you don't -- change it every 3 months, that is. Time is not as important an interval, as the engine running time is (milage). The main reason for most manufactures using 3 months OR 3,000 miles, is that if you haven't driven 3,000 in 3 months, chances are your doing a lot of short trips. This means the oil never really reaches a good operating temperature. The problem there is that moisture, from natural condensation, nevers get "boiled" off and tends to accumulate - creating acidic organic compounds that are corrosive. MOST drivers, reach the "3,000" mile mark before the 3 months; making milage a much more a important indicator of your oils useful life. However, if you happen to be one of those that do very little driving, or your vehicle sits for long periods of time, then the 3 month is a better general gauge. However, if your idle vehicle happens to be in a dry climate (desert) - then you could easily extend that time to 6 months or more. It's not that the oil goes "bad", it's the moisture contamination. Hope this helps clarify a little.

Answer 3

Oil is used to lubricate the engine interior. In the process the oil picks up small particles of metal and combustion gases from inside the motor. This damages the oil as well as reduces its ability to lubricate the internal workings of the motor. The combustion gases that leak past the piston rings inside the motor are quite nasty and hot. The gases combine with the oil and eventually wear it out. On top of all this, add moisture that gets in there also. So, the absolute very best way to protect your engine is with a good oil. Never buy the cheap no-name type. Also, if you live in the south where it gets real hot, use a heavier grade of oil, like 10W40 or 20W50 during the hot months. In the cooler winter months use 10W30 or 5W20.

Answer 4

Because the viscosity will break down over time and will not lubricate as well. Heat from the engine and using the oil as a lubricant will also cause it to break down. People that think oil doesn't wear out are wrong. I personally just go 2000-3000 miles and not worry about the time. We've had alot of vehicle last over 200,000 miles doing that. Unless it's been a year since you've changed your oil, I don't worry about the time much.

Answer 5

It doesn't go bad, it gets dirty.
Oil acts as a lubricant between moving metal parts in your engine, it also acts as a coolant, and a detergent.
So tiny little bits of metal, carbon, etc are constantly wearing off of your pistons, walls, rings, seals, and so forth...the oil carries them away from the moving parts and they (hopefully) get trapped in your oil filter.
You have to change it to keep this all going well, otherwise the oil gets too dirty and can't do it's job effectively.

Answer 6

You don't.

The recommendation you'll get from most good mehanics is every 5000 miles (or annually) which ever comes first.

Engines subject oil to high temperatures and pressures, dirt, and metal particles which do not exist in nature. Also remember that motor oil is a refined chemical -- not crude oil in the ground.

Answer 7

you don't have to change it ever. of course, as it collects dirt and starts breaking down so it no longer actually lubricates, you could end up buying a new engine. Newer cars don't always need a change so often - my Mazda suggests 7000 miles for average driving and 5000 if you do lots of short trips or live in hot humid or dusty envirnment.

so RTFM.

Answer 8

Due to the heat and friction of the engine this in turn breaks the bonding molecules of the oil down to where it no longer works as a lubricant. And engine without lubricant will expand due to the heat in turn locking up the pistons and engine in turn making the engine worthless.

Basic chemistry.

Answer 9

Engine oil is a chemical, not crude...... lmao..... it does comes from the ground. (except some synthetics)


The 3k or 3 month deal is really just to make more money....... sometimes that fits into your driving habits, sometimes it doesn't...
short trippers where they barely would make 2k in 6 months should do 3 months.... just to remove the fuel diluted oil, and water.

Answer 10

Crude oil may be that old, but the oil you put in your car is refined and has additives in it. The oil can break down from moisture and other things in the environment that get into it, as well as any gas that may run down your cylinder walls that doesn't get burned.

Answer 11

You don't. Check your cars maintenance schedule. Most say 5000 miles. The oil change companies want you to spend more, so they recommend that you change it sooner.

You can go 10000 miles with synthetic oils.