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Unread 09-16-2008, 08:13 PM   #1
mailforjon
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can i mix 5w-30 and 5w-20 safely?

so i just changed my oil and now realized that i bought 1 gallon (4qts) of 5W-30 and 2 qts of 5w-20 by mistake.

i was entering the change in my maintenance log and realized on the receipt that the two quarts were different.

is this a problem if i plan on driving 900 miles tomorrow?

im such a bonehead.

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Unread 09-16-2008, 08:15 PM   #2
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Dunno on the 4.7. . . If It was the 4.0, Id say just throw it in there. They will eat anything.


Ive done it in the past with other motors and never had any problems. . . Others may say different tho.
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Unread 09-16-2008, 08:19 PM   #3
Windowsrookie
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Stick with 5W-30 in the 4.7
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Unread 09-16-2008, 08:20 PM   #4
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Quote:
Originally Posted by mailforjon View Post
so i just changed my oil and now realized that i bought 1 gallon (4qts) of 5W-30 and 2 qts of 5w-20 by mistake.

i was entering the change in my maintenance log and realized on the receipt that the two quarts were different.

is this a problem if i plan on driving 900 miles tomorrow?

im such a bonehead.
If it were me, I wouldn't give it a second thought, especially with the cooler weather.
Look at it this way, you now have 5W-26.6 in there.
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Unread 09-16-2008, 08:23 PM   #5
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Quote:
Originally Posted by Windowsrookie View Post
Stick with 5W-30 in the 4.7
no foolin. that was my intention but i somehow grabbed 2 qts of 5dubya-20 on accident.

thanks for all the responses. it usually takes me 4 months to get to even 3k miles so i should be well into the new england winter on this new "blend".

edit: found the following site, which is very informative

http://micapeak.com/info/oiled.html
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Unread 09-16-2008, 08:32 PM   #6
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it'll be fine lol my MJ has a quart of reg oil in with synthetic she burns a lil oil and well i only had reg oil
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Unread 09-16-2008, 09:21 PM   #7
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Can You?? It seems you already have!

Should you?? No you should not!!!!

Mixing 5w/30 oil with 5w/20 oil and running it in a 4.7 engine that was built for a 30w oil is not a good idea!

Your engine was built with tolerances to be lubricated a 30w oil, not a 20w oil. This may seem to be a small difference but it is not!!

I'll assume your engine is not new and has some miles on it, going up in oil weight to a high-mile 40w oil might be OK but going down to a 20w oil is a very bad idea! Change it out to the right oil weight.
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Unread 09-16-2008, 09:25 PM   #8
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Is risking damage to your engine really worth the 25$ it will take to change the oil to something that is recommended?
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Unread 09-16-2008, 09:36 PM   #9
elmer_fud
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the 5w part is how much thick the oil is in the winter, and when it is cold

the 20 and 30 parts are how thick the oil is when it is hot.

I am not advising for or against this, I am just trying to give you accurate information.
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Unread 09-16-2008, 09:51 PM   #10
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Quote:
Originally Posted by RedEagle View Post
Can You?? It seems you already have!

Should you?? No you should not!!!!

Mixing 5w/30 oil with 5w/20 oil and running it in a 4.7 engine that was built for a 30w oil is not a good idea!

Your engine was built with tolerances to be lubricated a 30w oil, not a 20w oil. This may seem to be a small difference but it is not!!

I'll assume your engine is not new and has some miles on it, going up in oil weight to a high-mile 40w oil might be OK but going down to a 20w oil is a very bad idea! Change it out to the right oil weight.

it was my understanding (and as a previous poster alluded to) that as long as the specific type of oil was the same (in this case, valvoline maxlife), you can mix oils of any viscosity and the result will be something in between, but the result is not a linear proportion. Oil viscosity changes on a logarithmic scale, so calculating the result becomes very complex depending on the volumes of each type added.

i would venture to guess that with 2/3 5w-30 and 1/3 5w-20, that the net result would be somewhere in the high 20s. any mathematicians out there?
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Unread 09-16-2008, 09:58 PM   #11
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drain a little and put some 5w-40 in there?



My engine warranty requires 10w-40 the first 10k miles.
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Unread 09-16-2008, 10:01 PM   #12
mailforjon
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Quote:
Originally Posted by QuadraTokn View Post
drain a little and put some 5w-40 in there?



My engine warranty requires 10w-40 the first 10k miles.

i wish my engine was under warranty and it had less than 10k on it.

ive been reading on forums for other makes/models and the general consensus seems to be that as long as the brands/types are the same and the weights are similar, there shouldnt be an issue.
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Unread 09-16-2008, 10:07 PM   #13
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Do you wish you still owed someone $3500 for it?

I think Im going to royal purple my next oil change at 10k.


For your situation though, its not optimal, but I honestly dont think it would hurt anything
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Unread 09-16-2008, 10:20 PM   #14
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OP,

You don't have anything to worry about. While 5w-30 is the idea engine oil, running partial 5w-20 will not damage anything.

RedEagle is overreacting some. 5w-20 will be slightly thinner then 30 but not to the point of damaging anything. At the very worse, it might allow some oil to escape beyond the rings resulting in some burn off.

Some of you who are interested in learning more about oil would really enjoy www.bitog.com (Bob is the oil guy.com) and find it very educational.

Don't worry about changing your oil before your trip, just make sure you put 5w-30 back in on your next change.
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Unread 09-16-2008, 10:23 PM   #15
mailforjon
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Quote:
Originally Posted by QuadraTokn View Post
Do you wish you still owed someone $3500 for it?
thats not a bad payoff considering it only has 10k on it.

i was looking at financing about 15k for a WK w/ 18k on it.
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