why change oil after 3 months?

[BerniniCaCO3]

Hi!

This is more of a thought question.
And btw-- I'm not debating 3 months versus 4mo or 6mo-- I'm debating 3months versus a year or three years.

If you've got oil sitting in a plastic jug, it can last DECADES and still be good, so I understand. It's just sitting in a plastic jug

So if your family has 3 cars, one for mom, one for dad, and one SUV for family vacations and plywood from home depot that only gets driven 2000 miles in a year... do you still need to change the oil more than once in 18 months?

If so, why? After all, it's just sitting in the oil pan, like oil sitting on a shelf, not doing anything.


I'm not doubting per se, but I do want to know why this is the way it is!


thanks!
-Bernard

[1990LTD]

it gets contaminated/diluted


usually short trips are the hardest on oil. i think it's because the majority of the wear in an engine occurs during cold operation when the engine isn't up to temp yet. just because the temp gauge reads normal doesn't mean ALL of the motor is up to temperature

[BerniniCaCO3]

OK-- so this is overthinking it, but if the one time a car got used was for a 1800 mile trip out to the midwest and back (i.e., long highway miles), then that oil might be good for many months-- if those same 1800 miles were accumulated in a year of going to sunday church, it would be in greater need of being changed....

-Bernard

[mrltd]

it will turn acidic, once it's in a car it degrades quicker. If it's synthetic it'll last longer.

As for the short trips, it's hardest on oil because it doesn't get warm enough to evaporate the water that condenses in the motor.

I've pulled motors apart that were filled with jelly, old oil that had degraded over the years. It was long before synthetic was around.

[1980c10]

Pretty much short trips cause condinsation in the crankcase whice get water in the oil. Oil also breaks down overtime and does not lubricate as well even though the 5 year oil in the plastic jugg may look good, it may no have the same lubricating quality as brandnew oil. If nothing else change filters every once and awhile. My moms mustang maybe gets 500 miles a year at the moment and we change it every 3 months and change it and put fresh in right before it get put up for winter.

[cld783]

So if your family has 3 cars, one for mom, one for dad, and one SUV for family vacations and plywood from home depot that only gets driven 2000 miles in a year... do you still need to change the oil more than once in 18 months?



-Bernard

it's just a basic guideline schedule for oil change intervals. mostly refers to vehicles that are driven daily, so if you forget the miles driven you'd have a time frame to go by.

nobody can tell you for sure if the oils still good but it's good practice to change it anyway. in that case probably every time it's sat a long length of time and every 3000 miles in between.

[zoomie]

ive seen what happens to motors that ppl dont change thoe oil in for a year usually the cam lobes go kaplooey

[v8only]

not with my 5.0 roller cam motors...I have a couple of 5.0's...one in a 66 mustang...I drive the mustang maybe 1000 miles a year, so I basically don't change the oil but every couple of years..I just run a synthetic and .it's just fine.

[1987cp]

not with my 5.0 roller cam motors...I have a couple of 5.0's...one in a 66 mustang...I drive the mustang maybe 1000 miles a year, so I basically don't change the oil but every couple of years..I just run a synthetic and .it's just fine.

Is the '66 driven only in warm weather and kept in a heated location? Seems that'd make the above plan work much better than, say, with my seldom-driven stuff that sits in the driveway all the coldish-and-superhumid Michigan winter.

[v8only]

yea....california...78 degrees year round

[Tiggie]

We always stick to 3K miles on anything modern with a filter. In my daily drivers (wagon and '95 Ranger), I drive about 6K a year. That's an old change every six months. There is absolutely no reason to change it sooner. They are driven 3+ times a week on the highway for 20 minutes to work, then home again.

I have tried to stick to 3K changes in my Mustang also, which goes 3K about every year and a half. I try to drive it so that it needs an oil change before winter. I wouldn't let it sit all winter with 2900 miles on the oil, but I won't change it if it's just 1000.

Never use old oil. I had some Quaker State 10W-30 out of my Grandpa's garage when he passed away. It looked funny - kind of translusent and not transparent. I put some in a jar on the workbench and over a week's time, it separated into parts. The oil wasn't that old, but old nonetheless. Maybe fiveteen years? It was in plastic bottles. Good thing I didn't use the cans he had.

I will check the pH of the next oil I change. It will be my Ranger in about a month. The benefits of being a teacher - your very own pH probe.

[Mercracer]

yea....california...78 degrees year round

Unless you have a climate controlled garage, those 50 degree (or lower) winter mornings are giving you condensate in your motor....

[v8only]

i'm not worried about it. At risk of sounding like a complete moron, paranoid oil changes are just that...In daily driven vehicles I change the oil every 6-10k....that's what the manual suggests anyhow.

My father abuses cars like I've never seen anyone abuse a car....he doesn't change his oil or filter, period...just doesn't care. He drives so much, that he picks up another beater for a few years....he drives 30-50k a year and I've seen him go year after year in his cars doing nothing other than adding a quart if/when needed. Engines can take a beating....he's got an 86 ttop right now that we built with an explorer motor and an 86 ssp coupe, and they take his beating and keep on going.

I've never blown a motor in my life at age 36. I maintain my vehicles, but I do get a little lazy on the intervals...but from my experience and education, I sincerly believe that a lot of people out there are throwing away perfectly good oil and changing it way too often. Hell, we had a turbo charged 03 jetta at one point...the manual said 93 octane required and sythetic oil recommended. We put in dinasaur oil , and doubled the recommened change intervals at times, and ran 87 octane in the thing...I wasn't paying for premium in a freaking jetta.....65k miles when traded in, and it still ran like new and didn't burn a drop of oil.

[johnunit]

the premium fuel recommendations ARE optional in most modern cars. Premium fuel is only "better" in terms of octane rating, so all that happens is if the car starts to ping from 87 octane it'll pull some timing out and you're all good. However, in a lot of cars the decrease in timing to ward off detonation hurts fuel economy enough to more than negate the savings of cheaper fuel. My crown vic is like that, and so is my friend's base model audi A4.

Oil changes though, pretty much anyone whose worked in a commercial shop will tell you what long oil-change intervals can do. 7K miles you might get away with, but 10K miles on dino oil is just asking for trouble. There's a reason your dad didn't KEEP those cars he doesn't change the oil on.

[v8only]

fyi, our 2000 jetta had 10k oil change intervals per the owners manual. As far as my father goes, I certainly don't condone what he does...however the reason he goes through cars is because when he buys them, they're usually already 20+ years old and burn a little oil....each and every single car over the years has blown up from him just not adding oil...he runs it till it's dry...man you should see some of the connecting rod bearings I've pulled from his cars. One on a 22r 77 celica was welded to itself and welded to the connecting rod too, lol.