Mixing Engine Oil

[BZR4AGE]

Hi All

My car is due for an oil change and I always do the change myself.

I usually buy a new 4L bottle each time, so there is always some left in the bottle. I've come to a stage where I have so many bottles that I can do one complete fills from my "left overs".

My intention is:
1) Drain existing oil from engine
2) Fill up with all of my "left overs" (mixing different grade and a mixture of mineral and synthetic)
3) idle the engine till normal operating temperatures
4) Drain oil
5) replace oil filter
6) fill with completely new bottle of oil (not mixing)
7) DONE.

Will this be a good idea? I thought by doing this i can get some extra unwanted stuff out of the engine. Or is mixing oil a BAD idea (remember it will only be used once at idle speed)??

Any thoughts?

[MR2BOY23]

Maybe just using an engine flush might work better? Im no expert or anything but I dont think it would do much harm, mixing oil just decreases the performance as far as I know.

[Heylin]

Id spend $10 and run some STP engine flush through it, more effective than just rinsing it with fresh oil.

[BZR4AGE]

Did a bit of research and also from memory an discussion we had on this fourm, it appears that those engine flush stuff can actually do more harm than good..., thats why I never used them...any thoughts?

[Twolitre]

It won't do any harm but will it do any good? Why do you keep changing viscosity anyway? by the sounds of things you do enough regular oil changes to prevent sludge from building up in the first place. I'd just keep the oil for a mates "shitter" or top ups etc.
Pretty sure you can mix mineral with semi synthetic oil but not with fully synthetic, a quick google search would clarify that.
If your cars like mine and seemingly drips forever let it drain overnight like I do if you want to get as much of the old oil out as possible.

[BZR4AGE]

Thanks Twolitre

I always try to get the same grade (10w40), but in occassions I've used (10w50, or 5w40) depending on what deal my mate at repco can get me.

I change oil at every 5000ks

What about mixing semi-synethic with full synethic?

Because all my left overs been sitting for so long and it came to a stage where it is taking a lot of space in my garage, so I thought I will put it to some good use by giving my engine a "flush"

Cheers

[Heylin]

I change oil at every 5000ks

I got my Mr2 with 116,000kms on it. I have always changed the oil every 10,000 and always with Valvoline VR1 Semi-Synthetic (previously Durablend). Its now got 219,000 and engine is still great condition, holds 16psi boost and isnt shitting itself yet.

I know you dont save much overall by doing it sooner, but for a street performance car I would say 8000 - 10,000 kms is adequate change interval, any sooner is just a waste of time and oil.

It won't do any harm but will it do any good?

Im sure for a high K car with unknown history STP engine flush is brilliant, I used it for my first 2 oil changes.

The thing I reckon thats made all the difference in my oil and engine life though is ProMa MBL8, ive been using this in my SW20 MR2 for 6 years, 2 years in a AW11 and 4 years in a HB Mazda Cosmo.

$35 a bottle and does 3x 4 cylinder oil changes.

[themaleman]

i use proma 2, good stuff! my mates old man in a distributer so hit me up if u need any

[gepsk8]

use wynn's or good shit, not stp its crap
i would just mix the oil's and do 5k's (just watch it does burn it) depend on how old ur car is?
what is worth to u?(runabout cheap car/ur toy with hours of love put into it)
regular oil changes like that keep the engine clean of sludge, it will be fine as long ur not mixing 5w30 with 20w50

[BlakJak]

Because all my left overs been sitting for so long and it came to a stage where it is taking a lot of space in my garage, so I thought I will put it to some good use by giving my engine a "flush"

Cheers

The alternative suggestion here is to use the same oil each time (i.e. I use semi-synthetic 10w40) and at the start of the change, use the remaining oil from your last change. That way it doesnt sit on the shelf for ages, and you only ever wind up with one 'leftovers' bottle.

[Stealer Of Souls]

Can't imagine you'd do any real harm by mixing oils.. it's all a slippery compound designed to lubricate engine parts.... I've seen a few blogs and stuff from supposedly knowledgable car people with years of "practical" experience, and they all say at the end of the day oil is oil. It is better to not mix (more so semi with full synth) but if you have to then don't fret. Just don't expect the proper high levels of performance.

As an alternative suggestion - And it seems like you aren't adverse to basically throwing out the "scraps".
Drain.
Fill with scraps and some flush.
Run to temp and follow flush instructions.
Dump.
Fill with good stuff.

I've done this before when I first got an engine, but just used some nasty cheap stuff. It's amazing what the oil comes out of the engine looking like considering it's only been in the engine for like 15 minutes....

[BZR4AGE]

Cheers for that guys. Will take the advice and do the change.



themaleman, what Proma item should I be using? where are you located? Can you get those stuff from repco? cause I got a good mate that works there and gives me cost prices

[Bling]

Is this for a 20v? If so how do you end up with oil left?

I use almost 4L of oil between changes, so any left overs in the bottle are soon added to the engine

[BZR4AGE]

Hi BZGBling

Yes it is for a 20V. My engine is only around 40,000ks old as I've rebuilt it 2 years ago. So it don't burn any oil at all. I never need to top up in between change after rebuilt. And I think everytime I have about 1L left from a new bottle after changing oil. So now I have about 6 bottles of 1L left sitting in my garage

[Heylin]

themaleman, what Proma item should I be using? where are you located? Can you get those stuff from repco? cause I got a good mate that works there and gives me cost prices

MBL8 Concentrate for your oil, pre mix with your 4L pack of oil before adding to your car. 250ml bottle will do 3 x 4 cylinder oil changes.

The petrol treatment is good stuff as well. PT5, 500ml bottle at around $32 will treat about 15 tanks of gas, keeps your plugs and injectors clean, has top oil for upper cylinder lubricant, and improves the burning of the fuel.

Proma is only available from distributor, you can call their Auckland office and they will give you a list of distributors for your area.

[RunningRich]

The additives sound like snake oil to me.

On a modern car if your plugs are getting dirty your car is not tuned right or you have the wrong heat range IMHO.

[ke25sr]

I have been trained by Valvoline and told

DO NOT MIX OILS IN ANY WAY.

[tim_blair]

hey ive just done a paper on luberication systems

and mixing oils can be very bad especially between type (mineral, semi and fully synthetic) because they dont actually mix with each other and you can end up with one type of oil in a gallery while the other type is trying to get in but coz they dont mix they block each other im sure you can imagine what this can do to your engine

one of the best ways to flush your engine is to use kerosine because its very affective at breaking down oils and depostis but it also lubericates at the same time so therefor minimises engine wear

i usualy just use the stp stuff but make sure you dont run it for to long coz they can cause damadge

[BZR4AGE]

Hahahha, due to two voting against mixing oil, i will certainly not mix it...and it makes sense too from what tim is saying. Cheers

[frost]

just be careful with the STP and any other engine flush (or other cleaning agents) if your engine is already sludged up then its best to leave the sludge where it is, because its not doing any harm just caked on where it is, but it will do damage if you run a cleaning agent and break off the caked on stuff, it then can block oil drains, galleries, and oil pick up filter.

also on the matter of mixing oils, your always going to mix oils because there is always at least 150ml - 200ml left in your engine after draining. no matter how long you wait for the drips to end, or you could take your sump and oil pump off every oil change.