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Author Topic: motor oil weight.... can you mix it?  (Read 9849 times)

Offline postmaster

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motor oil weight.... can you mix it?
« on: March 01, 2011, 07:11:30 PM »
Although this may sound dumb, I have a question.  I do understand that the "w" on motor oil is not weight it means winter.  The lower the number the colder temperature the oil can lubricate properly.

That being said, my 1978 Honda service manual states that 10w40, 15w40 or 20w50 can be used.

Can I use 5W40 safely?

What happens if oil weights are mixed.  What if I mix 5w40, 10w40, 20w50 and 5w30?

Any harm or, just don't do it?

What cha' think?

Offline catang5oh

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Re: motor oil weight.... can you mix it?
« Reply #1 on: March 01, 2011, 07:21:31 PM »
I dont know if its true, but i have always been told mixing weights was a big no-no because different weights sometimes have completely different additives which in turn can cause erratic wear patterns in your engine. The 5w, 10w etc is a measurement of how fast the oil actually reaches full lubrication from startup, i quote this from a Hot Rod Mag.It shouldnt matter what 5w or 10 w you use as long as isnt energy conserving( thats the additives that screw up clutches)

Just my 2 cents, oil is about as volitile a subject as politics!
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Offline wweaver11

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Re: motor oil weight.... can you mix it?
« Reply #2 on: March 01, 2011, 07:46:56 PM »
I've always been told no.  But now I'm sitting here trying to think if I was ever given a reason why not?????

Offline bassguytom

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Re: motor oil weight.... can you mix it?
« Reply #3 on: March 01, 2011, 09:24:17 PM »
Don't mix synthetic and dino juice.  You knew that.

You can mix similar oils...10w30 and 10w40 mixed in equal parts makes...10w35. 
5w20 and 5w30 makes 5w25.
5w30 and 10w40 makes 7.5w35.

The list postmaster asked about just makes a mess.  LOL

You might not want to mix dissimilar brands because of potentially different additives. 

I had 2 partial bottles of Castrol Syntec one 10w30, one 10w40.  I needed some oil for my generator.  It worked FINE and still is working fine!   

weirdbeard

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Re: motor oil weight.... can you mix it?
« Reply #4 on: March 01, 2011, 10:10:42 PM »
  Why mix them at all?      {1}

Offline ironslede68

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Re: motor oil weight.... can you mix it?
« Reply #5 on: March 01, 2011, 10:19:22 PM »
if you need oil, the wrong oil is better than no oil. i usually put one type of oil in my bikes.

that being said. i used to do oil changes for people and i had a catch pan that drained into a quart can. you put "empty" bottles in the catch and before long i have a whole quart. needless to say i didn't buy oil ever for my own. i used this oil with new filters and never had a problem.
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Offline postmaster

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Re: motor oil weight.... can you mix it?
« Reply #6 on: March 01, 2011, 11:04:26 PM »
This is why I ask.  I have one of those nifty little drain thingy's that catch all the remaining oil in a quart.  Now I have about 4 quarts of combined oil.

Online springer

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Re: motor oil weight.... can you mix it?
« Reply #7 on: March 01, 2011, 11:38:46 PM »
if you need oil, the wrong oil is better than no oil. i usually put one type of oil in my bikes.
 
I had the pleasure of taking a class in Hydraulics from a man who retired from a major oil company. He spent 20 years in the research and development department of motor oils. Needless to say we asked him a few questions.
 Mixing different oils were one. His answer was like Sleds, any oil is better than low oil. The different between brand is almost nill. (The companies regularly analyze each others products) he said if it was him and the oil was low he would;
 1. Use the same weight, same type, and brand of oil
 2. If the same weight can not be found in that brand, use another brand, same weight.
 3.If the same type ( SD, SE, etc..) Can not be found then use what you can find in the same weight and change the oil at your first chance.
 4. If the same brand, same type, same weight can not be found then use what you have to but change it at your 1st chance. 
 5. The brand of oil dose not make a big difference as any of the major brand are of high quality.
 6. Do not use remanufactored oil. This is oil that has been used then "cleaned" to remove containments. (Carbon, gasoline, dirt, etc....)
 There is more but some of what I was told would just piss some of ya'll off. I will say this what that guy told me made good sense. And with 30 years in the making and develop of oils he should know what he is talking about.  Way more than you, me, or the guy at the quicky oil change place. Needless to say I will follow what he told me.
 Plus he was a very very good hydraulic instructor.
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Offline postmaster

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Re: motor oil weight.... can you mix it?
« Reply #8 on: March 01, 2011, 11:54:32 PM »
I'll just stick with 10w40 motorcycle oil to aovid any problems


Offline bassguytom

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Re: motor oil weight.... can you mix it?
« Reply #9 on: March 02, 2011, 07:46:13 AM »
Good info Springer.

Thanks.

I feel hydraulically edu-ma-cated now.   :)

Offline catang5oh

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Re: motor oil weight.... can you mix it?
« Reply #10 on: March 02, 2011, 11:27:47 AM »
I'll just stick with 10w40 motorcycle oil to aovid any problems



Thats what i have done, especially since Castrol started making Cycle specific and selling it at Autozone for the same price as Auto oil!
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Offline lazeebum

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Re: motor oil weight.... can you mix it?
« Reply #11 on: March 02, 2011, 01:49:35 PM »
Unless you like to replace clutch plates, use oil labeled for motercycles.
I did not buy my motorcycle to be a conversation piece, or fashion statement.  I bought it to ride.

ironbutt

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Re: motor oil weight.... can you mix it?
« Reply #12 on: March 02, 2011, 02:35:57 PM »
My experience indicates that if the manufacturer specifies 10W-40 and you run 5W-40, the engine will perform just fine, i.e. no additional bearing wear shows up in oil analysis, no oil pressure problems, no measurable increase in oil consumption unless the engine is already worn and used for a lot of stop and start short trips where it never gets up to operating temperature. 
However, if the engine oil is shared with the transmission, my experience has been that the shifting action or "feel" will be much less smooth with the 5W as compared to the shifting action with the  mfg recommended 10W.  Therefore, if the mfg says 10W, I don't like to use 5W unless there is no other option.
FWIW, IMO, YMMV,

Offline Rattletrap

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Re: motor oil weight.... can you mix it?
« Reply #13 on: March 31, 2011, 08:36:25 AM »
The definitive website for all oil questions I've found is "Bobistheoilguy", lots of oil questions and info and a quite a few oil engineers.
When in doubt, gas it

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Offline TALLADEGACHESSIE

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Re: motor oil weight.... can you mix it?
« Reply #14 on: March 31, 2011, 11:11:18 AM »
The only no no that I have heard delt with cars or trucks and cars or trucks that use Quaker State.  I had always heard that Quaker State was a parafin base which would build up on cylinder walls and slow down any leaks you had.  If you then put a asphalt base oil like Havoline it would cause the parafin to break down into a sludge.  Maybe someone else knows if this is true or not.  I really do not know that Havoline is asphalt base or that Quaker State is parafin base.  Just something I heard along the way. FWIW
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