Mixing different grades/brands of oil

[Flyingpony]

Is it safe to do, or is it a big no-no?

Had a look at the my collection of partly used oil bottles and added up their volumes, and I got thinking... This question can apply to anything thing which requires oil such as diff's, gearboxes, engines and 4wd transfer cases.

For my FXR I've got enough engine oil for a change but only if I mix two brands of different grades together. Part of me said it's safe because they're both designed for the bike engine but, part of me said don't because they'll react with each other being from different brands and of different grades.

For example, what I've got is Castrol Racing 4 (?) fully synthetic (green bottle) and Shell Advance 4 semi-synthetic (blue bottle).

What is the general consensus about mixing oils of different brands and grades together if both are designed for the same application?

[vifferman]

Is it safe to do, or is it a big no-no?

Can't see a problem with it myself.
Go for it!

[WRT]

Can't see a problem with it myself.
Go for it!

What he said, but let us know if it blows you your engine, Flyingguineapig.

[Crisis management]

I wouldn't mix different types of oil...ie. semi and fully synthetic. I would mix similar oils from different suppliers.
In the interests of science (and us) however, I think you should try it and keep a good record of the results.

Seriously, I know oils expensive but so's an engine rebuild. I always look after the oils and tyres, they are the the most important parts of a bike.

[FilthyLuka]

I always look after the oils and tyres, they are the the most important parts of a bike.

forgot brakes... never be a cheap mofo when it comes to brake pads! Its either a extra bit of $ for good brake pads or a lot of $ for the panel beating bill for that ferrari's rear bumper!

[ManDownUnder]

Highly stressed engines want good oil. If you race (or hoon around) and want to be 100% certain all is goo - don;t mix it.

Me personally... no worries. If it's about the same grade and no darker than the oil in the motor... in she goes!

[vifferman]

I wouldn't mix different types of oil...ie. semi and fully synthetic.

Well...um... how do you think they get semi-synthetic erl then? Perhaps the synthetic bit and the mineral bit know to keep separate from each other or summat....

[Motu]

Put a bit of each in a jar and give it a shake - if it turns into gold you know you are onto something.Oils are blended,you can blend your own too.You just don't want them too far apart in viscosity range.

Cheap pads are great,I use them a lot in my business - they give very good around town braking,not so good for high speed stuff.Everything has it's application.

[Crisis management]

Well...um... how do you think they get semi-synthetic erl then? Perhaps the synthetic bit and the mineral bit know to keep separate from each other or summat....

You may have a point there.....good job I don't work for Castrol eh?

I don't know what goes into the blends / mixes so I don't mix them and unless I do know I'm not going to recomend someone else tries it.
Boring I know, but you don't get to be an old fart by taking risks sonny...

[Motu]

If you mix 2 different grade oils,you won't get a compromise between the two....like 10/30 and 20/50 won't turn into 15/40.You will get some parts of the oil being 10/30 and other parts 20/50.

I've seen hundreds of engines die from lubrication failure - but none from oil failure.

[Shadows]

I can't see any problem mixing different brands of oil, most of the stuff is produced by the same people, it just comes with different labels on the containers. They were all the same old dinosaurs to begin with.

I wouldn't want to mix products that have different viscosity ranges though.

[Flyingpony]

Interesting replies here and they're not technical either nor discussed the merits of each oil

Both of these oils have been used by my FXR. The semi-synthetic was used for one change after the engine was broken in on mineral oil and it's been on fully-synthetic ever since.

But generally it appears that the answer is don't do it. That's okay, this was just a thought. I'm was more wondering if anybody had done something like this and then the oil went all fizzy and bubbled out due to their different chemical background. Also, their respective viscosity ranges are quite far apart.

[Drum]

Did someone say technical? Check out this link to a .pdf titled "A study of motorcycle oils" .........

http://www.amsoil.com/lit/g2156.pdf

[Shadows]

Did someone say technical? Check out this link to a .pdf titled "A study of motorcycle oils" .........

http://www.amsoil.com/lit/g2156.pdf

That Amsoil sounds like the shiznit, dunnit.

[Grinner]

The Amsoil article is an advertisment made to make their oil look better than everyone else's. Do not believe everything you read.

Mixing oils is not a good idea especially across types ie synthetic / semi synthetic / mineral oils and or grades ie 10w 40's with 15w 30's etc
Incompatable oils can turn to sludge.

If you insist on mixing test them first, do what Motu suggests ie combine equal amounts in a clean transparent glass container, mix / shake well and leave overnight. If they are still clear and have not seperated into layers they are probably compatable.

Cheers