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March 4, 2011 8:40 AM   Subscribe

How to know if the oil in a car has really been changed?

I took my ten-year-old car to have the oil changed last week. Today it wouldn't start, so it was towed to a different garage; the mechanic says it needs a new alternator and battery and an oil change, as the engine oil is black. So--is the only possibility that one of these garages is lying? And for the future, how can I tell if the oil has really been changed or not? FWIW, the guy today was setting my Spidey-sense off--he was really pushing me to buy the more expensive battery and alternator and in general was very aggressive, while the other guys I've used before and they don't set off any alarm bells.
posted by Ollie to Travel & Transportation (21 answers total) 3 users marked this as a favorite
 
Look in your car manual for the part about changing the oil. It should tell you where the 'Dip stick' is located in the engine compartment. After you get your oil changed you can get a paper towel, open the hood, and check the dip stick. You check it by pulling it all the way out, wiping it off with the paper towel, sticking it all the way back into its slot/hole, pulling it all the way out again, and inspecting the end of it. Clean oil is amber brown and translucent. The oil mark should end somewhere between the recommended level indicators on the stick.
posted by carsonb at 8:44 AM on March 4, 2011 [1 favorite]


It's weird for a battery and alternator to both "go out" at the same time. I think your spidey sense might be right. Beware.

Look at the oil in a new quart some time - that's what freshly changed oil looks like. Put a drop on a paper towel and see how it looks as it soaks in. It's clear, and a nice light color. Now pull your dipstick and do the same with the oil on it. If it's black and sludgy, it's really old.
posted by fritley at 8:45 AM on March 4, 2011


You could send the used oil off for oil analysis to know for sure.
posted by zsazsa at 8:45 AM on March 4, 2011


New oil is clean and obviously honey colored. It would only become black after a few hundred miles of use in a dirty engine, and longer in a newer engine.
posted by Gungho at 8:46 AM on March 4, 2011 [1 favorite]


It's weird for a battery and alternator to both "go out" at the same time. I think your spidey sense might be right. Beware.

Not in a 10 year old car that may also have a 10 year old battery. Putting in just a new battery may solve the problem, and you'd know soon enough if you need an alternator too because the new battery would not be recharging properly.
posted by Gungho at 8:48 AM on March 4, 2011


you'd know soon enough if you need an alternator

A real mechanic can test both the battery and the alternator. Without proper tools, you might replace one, then wait and see. But this is not the procedure a capable mechanic would use.
posted by fritley at 8:50 AM on March 4, 2011


Actually alternators and batteries go bad together all the time. Often an alternator will go bad (volatage regulator usually) and while it still works it feeds the battery a bad voltage for charging which really shortens the life span of the battery. The battery is weak then and makes the already faulty alternator work harder and then it goes all the way bad. Of course the reverse can also happen.

And yea, old oil is black and smells bad. New oil is some kind of amber and smells like oil (open a new quart and look at it-it should look like that).

Check the car talk website (annoying laughing guys on npr that give car advice) for their mechanix files for a good local mechanic.
posted by bartonlong at 8:52 AM on March 4, 2011


nthing the dipstick option after the oil change.

Most car part places (like Autozone) will test your battery for free (they will do the work of hooking it up too), plus those guys tend to be pretty honest and upfront with advice. You might try that before you spring on the mechanic.
posted by I am the Walrus at 8:56 AM on March 4, 2011


the guy today was setting my Spidey-sense off--he was really pushing me to buy the more expensive battery and alternator and in general was very aggressive, while the other guys I've used before and they don't set off any alarm bells.

Anyone setting off the Spidey sense should not be trusted. You need a battery that has enough cold cranking amps to meet the rating for your vehicle. You want an alternator that is OEM equivalent. You don't need anything better than that.

Batteries and alternators do go out at the same time, essentially, the alternator goes bad causing a huge drain on your battery, which kills it. If you replace only one, you'll be replacing the other very soon.
posted by Mister Fabulous at 8:57 AM on March 4, 2011


I just called them back and told them to use the cheaper, after-market battery and alternator--he said it was too late, he'd already started the work. So, lesson learned there; I'll think faster next time. I did tell him to not do the oil change, though. If it wasn't done I'll go to my regular place and ask why not.
posted by Ollie at 9:04 AM on March 4, 2011


Besides the difference in oil colour the new spin on filter, if your car is equipped with one, should be squeaky clean.

fritley writes "It's weird for a battery and alternator to both 'go out' at the same time. I think your spidey sense might be right. Beware."

In the case of alternators with internal regulators a regulator going bad can cause the battery to receive way over 14V and destroy the battery requiring the replacement of both. And a ten year old car, depending on your climate, probably has a five year old battery ready to fail at any time.
posted by Mitheral at 9:06 AM on March 4, 2011


He can use the after market battery even after he started. Easy to switch. No issues. And he has to have attached the alternator to the car to not be able to use the cheaper one. Spidey sense is dead on.
posted by JohnnyGunn at 9:08 AM on March 4, 2011


Ollie writes "I just called them back and told them to use the cheaper, after-market battery and alternator--he said it was too late, he'd already started the work. So, lesson learned there; I'll think faster next time. I did tell him to not do the oil change, though. If it wasn't done I'll go to my regular place and ask why not."

Unless you authorized the work phone him back and tell him to pound sand; he shouldn't have pre- emptively started repairs. It's up to him to eat the labour cost of installing and removing parts that you didn't tell him to install.
posted by Mitheral at 9:10 AM on March 4, 2011 [3 favorites]


"I just called them back and told them to use the cheaper, after-market battery and alternator--he said it was too late, he'd already started the work. "

As Mitheral says, unless you specifically authorized that work, he's attempting to defraud you. This guy doesn't sound legit.
posted by Dipsomaniac at 9:37 AM on March 4, 2011


At the risk of babysitting this thread, just to be clear: I DID authorize the work--in our initial conversation, I told him I wanted the cheapest after-market battery and alternator, as I didn't think I'd have the car that much longer. He did the hard sell, I gave in. When I called back 1/2 hour later to insist on the cheaper stuff he said it was too late. Lesson learned.

I did tell him not to do the oil change, though, so I can at least get to the bottom of that. Thanks for your responses.
posted by Ollie at 9:45 AM on March 4, 2011


If you want to be sneaky, paint a small line of nail polish across the oil drain plug and the oil pan. If the line is unbroken after the oil change, they haven't removed the plug, so no oil was removed.
posted by doctor_negative at 12:37 PM on March 4, 2011


doctor_negative: unless they use a system that sucks the used oil out through the dipstick tube.
posted by zsazsa at 12:51 PM on March 4, 2011


In diesel engines the oil will turn black almost instantly after an oil change.
An oil change should also include a filter change,and its pretty obvious on most cars if you have a new filter.
posted by TDIpod at 1:47 PM on March 4, 2011


I'm not sure if it is still common practice, but back in the day (10 years ago), the "recomendation" was to change the oil every 3000, and the filter every 6000. The oil changers would write or paint an X on the oil filter in the intermediate change. And then they would only change filters that didn't come in with Xs on them. Write your own X.

If you pull the dipstick and put a dot of oil onto some white notebook or xerox paper, first before the change and then after, the splotch that forms from each sample will be different. Even if the oil turns black instantly. If the splotches are identical, you can bet the oil wasn't changed.

(Honestly, you can probably feel and smell the difference, but the above is a little more scientific.)

doctor_negative: unless they use a system that sucks the used oil out through the dipstick tube.

If they are, that's a sign to go to another oil change place. If they aren't cracking the drain plug, a lot of gunk is getting left in the bottom of the oil pan.
posted by gjc at 4:01 PM on March 4, 2011


I use my key and drag a scratch mark into the oil filter. Once I've had the oil changed I look to make there's no scratch on the new filter. I've had situations where they changed the oil but 'forgot' to replace the filter. Idiots. The new oil run through the old filter picked up a lot of black color.
posted by wkearney99 at 5:28 PM on March 4, 2011


When I called back 1/2 hour later to insist on the cheaper stuff he said it was too late. Lesson learned.

The lesson learned is "do not go back to that mechanic."

There is very little he can do to your car that would be non-reversible and "oh, too late." I don't know about you, but that's an unacceptable attitude for someone doing work for me. Go ahead and explain to me exactly what you have already done and what it would take, how much it would cost, to UN-do that. I'll decide. Swapping a battery takes ten minutes, there's no "too late" about it. "Too late" is non-responsive. It's pretty much, "gosh will you stop asking questions and let me do whatever I want and then charge you for it?"

He may be honestly doing what he thinks is in your best interest, but IT'S NOT HIS CAR. It's yours. Find someone that actually lets you make, and helps you make, informed decisions instead of bullying you to butt out and let him do what he wants.

(Plus, in my experience, that would have to be one bored-ass no-business maytag-repairman shop to have tools on your car within 30 minutes of the say-so. Sounds unlikely.)
posted by ctmf at 9:44 PM on March 4, 2011 [1 favorite]


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