Next oil change.....mixing?

[stygz]

Not sure if this will be ok but I was planning on using a mixed bag of left over oils for a Subaru Impreza 2.5 non turbo.

1 qt is mixed 5w30 M1 and PP
2.5 its of old Castrol Edge GB 10w30 (unopened contianers)
remaining will be M1 5w30

According to the OM this car can run most any weight oil all the way up to a 50wt.

Good to go?

 

[2cool]

You're fine. There have been threads about "frankenbrew" oil mixing almost from day one. NO ON HAS EVER, to my knowledge had engine damage from mixing oil. I have done it myself, and I have a blend of leftovers that I'm going to put in an old Mazda I have.

The only possible scenario I'd NOT recommend is to do this on a new vehicle with Gasoline Direct Injection. They are very hard on oil, and a mix might; and I stress Might, become an issue.

 

[69GTX]

In Georgia I wouldn't be concerned at all about mixing grades between 0/5w-20/30. My own preference is to try and not mix distinctly different add packs. Mobil 1 and older Castrol Edge synthetics were strong magnesium and lower calcium. The PP/PU/QS/MSS/FS/M1 0w-40 and most others are higher calcium and almost no magnesium/sodium. Then you have the other group like Valvoline, Mobil 5K, Shaeffer, RP, Lukoil, Peak, AZ, O'Reilly's, Brad Penn, etc. that have lighter Calcium and moderate sodium. I prefer not to mix between the 3 groups, though it probably isn't going to hurt anything. I figure if the oil producer wanted just one of these 3 groups....why should I mix it up to get a group that no one currently runs or certifies (ie a little bit of everything)?

 

[OneEyeJack]

When you mix you can't be sure of what you're getting. The resulting mixture might not then meed some or any of the spec's that either oil meets before the mix. How would you ever know. The idea that lots of people here do it and there's no evidence of damage is faint praise for such experiments. How would you ever know what damage is done beyond a dramatic failure? And besides, if you only keep a vehicle for a few years, who cares anyhow?

The cost of the oil itself is such a minor expense the question becomes why mix? The safe answer especially if you keep a vehicle is don't do it. Trust the oil company or go somewhere else. Remember, the oil is only guaranteed to be miscible. That leaves a lot of leeway for whatever might happen.

 

[HTSS_TR]

For a beat-up vehicle that you don't care, then mix away.

Otherwise, I only mix different grades of the same oil to get the desired viscosity. I did mix M1 0W20 with M1 0W40, Castrol Edge 0W40 with Castrol Edge 0W20 ...

 

[Y_K]

A mechanic friend has been running his Civic on his shop leftovers since his car hit 70k. Everything from Fedrated Oil to Motul. It has over 380k miles on odo now. Granted, it is a 'simple' NA engine

 

[CourierDriver]

I have 3 quarts of straight 30 wgt and one quart of 15w40 in my ancient 2005 Buick , L3800 engine,,,runs great,,,what can I say. Why, its warm here in Tn, .

 

[Shannow]

Originally Posted By: 2cool
NO ON HAS EVER, to my knowledge had engine damage from mixing oil.


http://papers.sae.org/932831/

Now you know of some.

Quote:
An investigation of an engine field-failure found low-temperature incompatibility to be the root-cause of an engine pumping failure. This was established from an examination of the rheology of the new and used oils. It was later discovered that some SAE multigrade oils that contain higher-cloud-point basestocks are incompatible with other same-W-grade oils that contain VI improvers that have a propensity to interact with wax precursors. The latter oils, which failed the Scanning Brookfield test, but not the TP1 mini-rotary viscometer test, were found to be incompatible with a number of commercial multigrade oils at low-temperature.


Two fully compliant oils were mixed (the new oil with the residual of the factory fill), and the oils became unpumpable, even at ambients above freezing, causing damage.

Now some will strawman me into having the opinion that ALL mixing will cause damage....I've never once said that.

I've only said that damage is rare, but it HAS and COULD happen.

Best defence is the Myagi defence "no be there", by either not mixing, or not relying on (say) two 0Ws to get your car started at -40C.

They all mix, they can mix be chilled to the freeze point be heated to 150C, and frozen without forming precipitates or separating...that's ALL that the test regime promises...and even THAT is only with a handful of reference oils, not every oil ever made.

 

[Shannow]

Originally Posted By: CourierDriver
I have 3 quarts of straight 30 wgt and one quart of 15w40 in my ancient 2005 Buick , L3800 engine,,,runs great,,,what can I say. Why, its warm here in Tn, .


SAE30, without VMs or PPDs is probably the most predictable of all oils to play mixologist with.

 

[AuthorEditor]

I've routinely used various brands of oil together ever since I've been driving and have never noticed much difference or had any engines fail on me. I try to stick to the same grade and spec of oil, but I think the chances of having a major problem are very, very low based on some 50 years of doing this. What usually happens is I need some top up oil in between changes and end up with a different brand. I try to stick to something of the same weight and similar type, but in the past I have done things like added some 10W-50 I had hanging around during the summer in my Crown Vic specced for 5w30. Engine seemed smoother and quieter with heavy stuff, and it was August so I was not worried about startup problems. I once got rid of some very old Amsoil I had in 10W-40 for 4-stroke outboards by running it in the old Crown Vic. Didn't notice anything.

 

[Plawan]

I do the same thing every once in a while just to use up left overs.

 

[AuthorEditor]

I should have added that it would probably depend on the vehicle and the oils involved. If I had an expensive new car on warranty I would avoid doing it, but I am usually driving inexpensive older cars and don't consider it a problem--though I won't dump 15w40 diesel oil in something specced for 5W-20.

 

[stygz]

This is going in a 2008 Subaru Impreza 2.5i with about 70k miles. We are probably trading it off next year. It's not really a beater but not new either. I cannot foresee a one time OC giving a problem but maybe prolonged OC like this could?

 

[A_Harman]

Originally Posted By: stygz
This is going in a 2008 Subaru Impreza 2.5i with about 70k miles. We are probably trading it off next year. It's not really a beater but not new either. I cannot foresee a one time OC giving a problem but maybe prolonged OC like this could?


Yes, running a Frankenbrew one time to get rid of partial bottles of oil is OK, but continually doing mixes of oils from different manufacturers may cause deposits due to unpredictable reactions between incompatible additive packages.

 

[BlueOvalFitter]

There is nothing wrong with using a Frankenbrew oil in your engine.
About a month or so ago I made up some M1 0W20 with other XW30, 10WXX, and 15W50 weights for our donated OCI's.
When Chevron Supreme was very plentiful a few years back I would mix it with WMST synthetic oil.

 

[Yup]

Doing it here and there I doubt would create any significant issues that weren't already going to occur in the engine. I've done it a few times in my Honda. It's running fine. Had an older Honda that didn't use a full 5 qts so would use that leftover with some new for my car. If you did it every time I doubt anything would happen, but I'd be a little more worried myself. Especially if it was a newer car. A car with over 100K miles...I'd do whatever. Cause it's worth less...