which is worse? running a quart low or mixing oil?

[jimbrewer]

Which is worse, running a quart low, or mixing oil?

A relative is a recent college grad. Working first job with a decent wage, but its kind of temporary. Dad (in another city) arranges to have oil changed on her old car with Mobil 1 at 5k or so when she comes to visit. Its the car she had in high school. The oil was kind of low I think a quart and a half the last time she dropped by for a visit and I happened to be there.

A couple of days later as she drove me to the airport, I told her she should be careful to check her oil every couple of weeks and keep it topped off. She didn't know how, but I told her any guy at her apartment complex would be happy to show her (one of the perks of being a nice looking co-ed type). Given her limited means, I told her not to worry about getting high-dollar Mobil 1, but to get any old name brand oil in her grade, and keep a bottle handy in her apartment. I suggested Mobil 5000.

Did I give her bad advice? Is it worthwhile to top off the oil now that they come in E-Z resealable screw top containers and not cans? Or should we still wait until the oil gets a quart low before adding more?

 

[JC1]

She should be topping off when it's low. Even if she doesn't have Mobil 1.

Regards, JC.

 

[demarpaint]

I think you gave her good advise. I'd rather have two different oils in the sump than be driving around low 1+ qts. of oil.

 

[Quattro Pete]

Originally Posted By: jimbrewer
Which is worse, running a quart low, or mixing oil?

Any oil is better than no oil.

Quote:

Or should we still wait until the oil gets a quart low before adding more?

Don't let it go below the "MIN" level on the dipstick. Anything above "MIN" and below "MAX" is OK, IMO.

 

[simple_gifts]

Quote:

Or should we still wait until the oil gets a quart low before adding more?


If she can grasp the % it is low on the D.S. and roughly decide how much oil to put in, she could top off any time; otherwise "wait until it touches the bottom line and then pour a whole quart in"

Sometimes it isn't the task, but the ability of the person who needs to accomplish it.

 

[Clevy]

There is nothing wrong with mixing oils and I would be more concerned with low oil level.
Your advice was sound. Tell her to top up when it says add on the dipstick. Once it gets to that point the engine will usually accept a full quart. And half a quart too much is no biggie if it does get slightly overfilled.

 

[TFB1]

Probably 50% low on oil isn't going to harm any engine...

I never add till it's at least qt low mark, sometimes not even then... Once left the '07 Grand Marquis a qt low after a change for several months, added the extra qt when I was leaving town for a few days...

 

[Chris142]

X2 on the any oil is better than no oil

 

[mongo161]

IMO....Whatever she decides....please tell her to avoid the Convenience Stores at the Filling Station/Gas Station.

Unfortunately, We've all seen the "terrible" garbage that can be sold to unsuspecting people, especially women, when they fill up at the station. Maybe, you could give her a link to the PIA site, for informative opinions, on which oil to buy and those to AVOID.

IMO....you could advise her, as a close family friend, to only seek advice, on her vehicle, for "TOP OFF" oil, at a reputable auto parts stores like AAP/AZ. The employees will help her and they could suggest some clearance oil, on special, which would be very good for topping off her vehicle each time it is low.

 

[ahoier]

I've always been told to only add when the oil hits at or below the "ADD" mark on the dipstick.....and on every car I've driven, when it's at that mark (pretty much, the end of the stick) a whole 1 quart bottle will take it to full - no need to "reseal" the bottle....

Now, there could be exceptions....but on the couple Fords, Hyundai, Dodge (88 Aries 2.2L....current DD), and a Saturn SL2 the dipstick seemed to work this way....

But yea, I wouldn't worry about mixing grades between OCIs......now if she's hardcore about going the 8-15k or whatever mileage Mobil claims their full synthetic can go.....THEN I'd say keep her with the Mobil 1.....but other than that, Mobil Super 5000 will make for a good top off oil (and it in itself is good for 5k,,,,again, according to Mobil )

 

[bigt61]

"Which is worse, running a quart low, or mixing oil? "

- running a quart low is worse.

 

[crazyoildude]

dont run low!
as for mixing oils that is not an issue

 

[jimbrewer]

Originally Posted By: TFB1
Probably 50% low on oil isn't going to harm any engine...

I never add till it's at least qt low mark, sometimes not even then... Once left the '07 Grand Marquis a qt low after a change for several months, added the extra qt when I was leaving town for a few days...


The "wait until its a quart low" thing is what I was taught. But in those days the oil came in cans and the temptation to overfill was higher, or at least the issue of proper disposal of a half can of oil was higher. Now, you can get a Mini-Cooper with, as I understand it, a 3.9 quart sump, or a Ford 5.0 Coyote engine with and an 8 quart sump. Seems to me its no big deal to run the Coyote a quart low. Mini Cooper? I'd worry a little.

There is another advantage to the "top off" advice it seems to me. People who might be haphazard about checking the oil like my relative, might be saved. Scenario I see is my relative checks a few times, adds a half quart to full then forgets for a few weeks. Checks again after a while. Car is a quart low, not a quart and a half low....

 

[uart]

Originally Posted By: jimbrewer

There is another advantage to the "top off" advice it seems to me. People who might be haphazard about checking the oil like my relative, might be saved.

That was exactly the point I was going to make Jim, you beat me to it.

It might be ok for someone who's really conscious of their oil to wait until it's a full qt low, or even lower. But for someone who perhaps isn't going to check the dipstick all that often it's not a good idea. Once you start running below the "add oil" level on the stick, things can go from being only a little bit bad to a whole lot worse in a fairly short time.

 

[TechnoLoGs]

I had thought that as long as the oil covers the pick-up tube that the low oil issue is a sabre-rattler. Not that low oil is ideal, but I had low oil in my vehicle for a moderate amount of time due to other mechanical issues and my oil pressure remained the same, not that my engine was happy, but my engine had some problems that are getting remedied now..

And it wasnt due to the oil...

 

[TFB1]

Originally Posted By: TechnoLoGs
I had thought that as long as the oil covers the pick-up tube that the low oil issue is a sabre-rattler.


As long as oil pressure is steady(covering the pickup), it makes little difference how much oil is actually in the engine... If it's low enough to be causing a issue, pressure will drop on hard acceleration or turns, of course neither of these conditions are good... Again unless it's going to be a full quart, I'll never add... Only partials I have around here are for my mowers that holds less than a quart...

For someone who doesn't have a clue what's happening inside their engine, it's probably best that they keep it nearly full...

 

[Garak]

Originally Posted By: TFB1
As long as oil pressure is steady(covering the pickup), it makes little difference how much oil is actually in the engine...

Agreed, within reason, of course. Being a quart low isn't a major deal over the short term. It's certainly not essential to grab the straight 50 on the garage shelf and do a top up, rather than driving the vehicle somewhere and picking up your preference. Nonetheless, there's no reason to run it low for any sustained periods. Bigger sumps have advantages, and shrinking a sump by negligence doesn't help matters long term.

 

[jrustles]

I'm surprised there aren't more in the "run it low" camp.

I would never run low, and I would certainly never run 50% low!!
If I was 50% low and had no choice but to drive that way, it'd be all sub 3K engine speeds, no more than 25% throttle and slow turns.

Imagine you have a 4quart sump and you're down to 2. You raise your engine speed and the oil is all pumped out of the sum and does not return in time, you're going to suck in air and aerate the oil. The rate at which oil returns to the sump is directly related to viscosity and oil system design. These two variable combine with the fixed parameter of gravity to define the rate of return.

Not just that, but you're now dealing with a 50% (or insert preferred value here) reduction in the thermal capacity of the lubricant. Simply put, there's less lube to absorb the heat from the parts and transfer it to the cooler or distribute it throughout the block. Not only will you run hotter, but your oil temperatures will average much higher, reducing the efficacy of the already compromised lube. The engine outputs a certain amount of heat to the oil for it to distribute through various cooling channels. When you reduce the capacity of the oil, not only are local hot spots left with less oil to cool, but this oil will be hotter, more likely to break down in turn creating more friction heat and exacerbating the problem exponentially until something fails, usually in this order 1)oil film 2)additive boudary layer 3)engine hardware. This has been my understanding and experience.

That said, I always top off- obsessively- at least anything below the mid-mark on the DS. I generally like to overfill my crankcases once I have an idea of the windage buffer of the particular engine.

 

[demarpaint]

If I was down half a qt. I topped up. Since I got rid of my beater I now have 3 vehicles which don't require topping up between oil changes.

 

[RobertISaar]

i generally check oil level every time fuel is added... if it needs a half quart of oil to hit the full mark, it gets it. anything less than that and it's not worth the trouble.

how far i'm into an oil change will also determine if it's time to just change the oil rather than topping it off. at a consumption rate of 1 quart per ~2000 miles and going nearly 500 miles between fuel additions, basically every other time i check the oil, it gets a half quart.