Mixing of various engine oils bad idea?: Fact or BS?

[Iamme]

I have heard that one should stick with not only the same weight oil for an engine...but with the same BRAND as well. What is the truth with this?

I have mixed oils in vehicles. I pull out the dipstick and I see a uniform coating of honey-like film on it. I see no separation or anything. So how on earth can these fluids not be mixing properly? Does one need a microscope to know the truth here?

Does anyone HERE know anything about this?

[Ove]

Since they all buy their oil from the same 2-3 reffineries it sounds like utter b******* to me. I took a course once on auto engines and the instructor was an old mechanic. HE tried very hard to stamp out some of the very persistent myths that lingered:

"Super" gasoline is allways better than "Regular" no matter how your car is ajusted .
You can destroy your engine if you put "high grade" oil in it.
There are oil additives that "repairs" your engine.

etc....


The best oil for most engines are a multigrade "5w 40" but most will run happily on "10w 40" or even "10w 30" what IS important is that it is changed regularily and that the filter also is changed.

Perhaps some of the additives that some oil companies add can have adverse effects if mixed but i doubt it.

[JSFolk]

I managed to get myself ticked off by posting a response to a thread about synthetic oils in a knife forum a few weeks ago. Someone orignally asked what was the "best" brand of synthetic oil to use for their car, and mentioned something about changing their oil every 2000 miles. I posted a link to the Consumer Reports article that concluded that as long as you have the little star-shaped ASPI (or whatever) symbol on the container, it doesn't matter which brand you buy, or if it's natural or synthetic. Furthermore, they noticed no difference in the cars they tested which had their oil changed every 3k, 6k, or even 12k miles. My conclusion that this guy was changing his oil 3-6 times more often than he needed (adding to oil disposal issues) and probably paying 3 times as much per quart as he needed for the useless synthetic oil.

Response to this? Nothing.

"My daddy always used Valvoline and...."
"I saw some engines taken down and the ones that used synthetic always looked just a little better...."

:hit:

[Benguin]

My car runs on LPG (Propane). One interesting observation from a couple of mechanics is that the oil doesn't look to break down at all, or turn black or whatever. Specifically, oil that's been in there for 20k looks, smells and feels the same as stuff from the bottle. I need to top it up a little bit now and then, but one of the mechanics postulated it didn't really ever need changing. We weren't really sure though, and it's an expensive experiment!

Is there any efficacy to the molybidmium additive? (Molyslip, Slick50 etc)

[Skeptical Greg]

Originally posted by JSFolk
I posted a link to the Consumer Reports article that concluded that as long as you have the little star-shaped ASPI (or whatever) symbol on the container, it doesn't matter which brand you buy, or if it's natural or synthetic. Furthermore, they noticed no difference in the cars they tested which had their oil changed every 3k, 6k, or even 12k miles.



Good reference..

Consumer Reports - Oil Test (http://www.xs11.com/stories/croil96.htm)
The bottom line. In our tests, brand didn't matter much as long as the oil carried the industry's starburst symbol (see "It's not just oil," article 3 of 4). Beware of oils without the starburst; they may lack the full complement of additives needed to keep modem engines running reliably.

[c0rbin]

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[Iconoclast]

Originally posted by Benguin
Is there any efficacy to the molybidmium additive? (Molyslip, Slick50 etc) Well, regarding Slick 50, Blue Coral and Quaker State were both ordered by the FTC (http://www.ftc.gov/os/1997/12/bluecora.do.htm) several years ago to (among other things) cease and desist from:

From the FTC order
B. Making any representation, in any manner, directly or by implication:

1. That, compared to motor oil alone, such product:
a) Reduces engine wear;

b) Reduces engine wear by more than 50%, by up to 50%, or by any other specific quantity;

c) Reduces engine wear at start-up;

d) Extends the duration of engine life; or

e) Lowers engine temperatures, reduces toxic emissions, increases gas mileage, or increases horsepower;

2. That one or any other number of treatments of such product reduces engine wear for 50,000 or any other number of miles;

3. That such product has been used in a significant number or any other number of U.S. Government vehicles; or

4. Regarding the performance, benefits, efficacy, attributes or use of such product
So, they can't claim that their goop reduces engine wear, makes them last longer, or increases fuel economy. Years ago NASA played around with teflon coating on bearings used in rocket engines -- note that they applied the Teflon directly to the bearing faces using a heat process, they didn't just pour it onto the engine as you do with Slick 50 -- and found no benefit. There's also a huge spiel floating about all over the internet all about how bad these products can be for your engine, but it's completely unreferenced so I'll make no mention of the claims made in it.

Note that although the US packaging of Slick 50 no longer carries the above claims, the product as packaged for other markets such as Australia still incorporates these claims. The Slick in Slick 50 refers to the advertising methods, not the product itself.

[Crow T. Robot]

Along the same lines, I had a friend (back in the '70s) who'se older brother owned a machine shop. He said he could ALWAYS tell when an engine he rebuilt had been owned by someone who used STP religously, because there was a big ole glob of the stuff in the bottom of the oilpan! He said that the oil temps encountered in a "daily driver" never reached a point where STP "melted" enough to blend with the oil effectively. It may have worked wonders in high temp racing applications, but it was pretty much useless for the rest of us...

[DaChew]

Oil change intervals should be based on not only your driving habits but also the areas in which you drive. If you live in an area that has high particulates in the air. You should think about changing oil more often. The additive packages and viscosity break down over time and that can be sped up or slowed down based on outside temperature, the condition of the engine, the dust conditions, the way you drive, etc... There really is not silver bullet answer as to how often you change oil. It depends.

Some place I have a copy of Hot Rod magazine in which they did a side by side comparison of regular Quaker State engine oil and Royal Purple full synthetic. They set up and engine on a dynamometer did a pass with the Quaker State then one with the Royal Purple and compared them. The Royal Purple made about 10 more horsepower. This was on a push rod motor set up for drag racing with (as I recall a bit over 400hp). This tells me that there is a slight advantage to synthetic. Is it worth the cost of synthetic? I don't think so.


I change the oil in my cars every 3000 miles because it's cheap. I use whatever major brand happens to be on sale at the time. My advice on engine oil has always been the same: Do it yourself and it's cheap enough to do more often than you probably need to and that can't hurt.

[Bearguin]

Originally posted by DaChew

I change the oil in my cars every 3000 miles because it's cheap. I use whatever major brand happens to be on sale at the time. My advice on engine oil has always been the same: Do it yourself and it's cheap enough to do more often than you probably need to and that can't hurt.

I agree with the first part but have actually stopped doing my own oil changes. I find the convinience of the quick lube places, plus the fact that they do lube my joints (which I never seemed to do) and not having to get rid of used motor oil is worth the extra $20.

Bear in mind that there is little I won't tackle on my truck. I've swapped engines, trannies, rear ends. I plan to change the top end of my motor (new manifold, heads). Only thing I balked at was changing my fuel pump as it meant dropping the tank and I get nervous around gasoline.

Mixing brands is fine. Stick with the car manufacturers recommendations for weight. Change your tranny fluid every so often. I've got synthetics in my diffs as I got some on sale, but just run dino oil in the motor.

[DaChew]

Originally posted by Gods Advocate


I agree with the first part but have actually stopped doing my own oil changes. I find the convinience of the quick lube places, plus the fact that they do lube my joints (which I never seemed to do) and not having to get rid of used motor oil is worth the extra $20.

The problem I have with the quick lube places is they won't JUST change my oil. Every time I take my truck in they want to change the diff oil. Why? Because it's easy because it has a drain plug. So they can pop in a couple liters of diff oil and charge me $35 for it. Plus, the one time I did agree to it because it was the middle of winter, they only about half filled it. Fortunately, I checked their work. They didn't get to all of my zerk fittings either. Plus, I've heard that some of them use recycled oil. I don't know if that's true or even if it's bad but they certainly don't advertise it.

My cars and truck have K&N air filters in them just because it saves money and time in the long run. The problem is, they're red. I've had two quick change places tell me I had major problems with my car because there was tranny fluid in the air filter. Of course, they had absolutely no explanation how that could possibly happen. One of them even tossed the filter in their dumpster without even asking they were so convinced I needed a new filter. The rep actually told me that having an air filter that dirty was a safety hazard so they had to throw it out. Needless to say one of his pit monkeys had to go dumpster diving for my $60 dollar filter after I told him he was buying me a new one. Maybe I should switch to the brand that are blue.

Oil disposal is easy for me because my city set up a recycling center. I'm told they sell the used oil for fuel oil so I feel like I'm doing an additional municipal duty.

[JSFolk]

Benguin, from that same Consumer Reports article..


"We also tested Slick 50 and STP Engine Treatments and STP Oil Treatment, each in three cabs. (Slick 50 costs $17.79 per container; STP Engine Treatment has been discontinued.) All three boast that they reduce engine friction and wear.
(snip)
When we disassembled the engines and checked for wear and deposits, we found no discernible benefits from any of these products.

The bottom line. We see little reason why anyone using one of today's high-quality motor oils would need these engine/oil treatments. One notable effect of STP Oil Treatment was an increase in oil viscosity; it made our 10W-30 oil act more like a 15W-40, a grade not often recommended. In very cold weather, that might pose a risk of engine damage. "

[WildCat]

Originally posted by DaChew


The problem I have with the quick lube places is they won't JUST change my oil. Every time I take my truck in they want to change the diff oil.
You need to find a new oil change business! Mine only asks me if I want to change the diff fluid at the appropriate (manufacturer recommended) interval. And they almost always tell me the air filter is ok, and even if it isn't (and I know when an air filter is bad) I'll just change it myself for half the $.

Living in the city w/ no garage I wouldn't ever change oil myself, I would only save $10 anyway.

Now, my sister ran her new mini-van all summer w/o ever changing or even checking the oil level. After spending $3500 for a new engine she learned the importance of it. :p

Of course, the next year she fried the transmission by driving 70 mph for 100 miles in low gear, apparently she didn't notice her RPM guage in the red or the extreme noise the engine must have been making. :p

[Bearguin]

Originally posted by DaChew


The problem I have with the quick lube places is they won't JUST change my oil. Every time I take my truck in they want to change the diff oil.

Never had this problem. They tell me my transfer case leaks but it's no big deal.


My cars and truck have K&N air filters in them just because it saves money and time in the long run.

I put the sticker that came with my K&N on the air cleaner and they don't even look at it.



Oil disposal is easy for me because my city set up a recycling center. I'm told they sell the used oil for fuel oil so I feel like I'm doing an additional municipal duty.

Here, any store that sells oil has to have a reclaiming facility. It's still a pain to drain it out of the pan, into the bottle and then remember to take it and pout it inot their drum. I'm not good at recylcling bottles either so it is easier for them to do it for me. Plus I get coffee and a paper.