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73-87 Chevy _ GMC Trucks => 73-87 Chevy & GMC Trucks => Topic started by: philo_beddoe on June 30, 2016, 06:48:40 pm

Title: Mixing oils
Post by: philo_beddoe on June 30, 2016, 06:48:40 pm
Is it safe to mix engine oils, like using several different brands, (all 10w40) on an oil change. I received a couple cases for free of mixed name brands.
Title: Re: Mixing oils
Post by: boulky12 on June 30, 2016, 08:33:23 pm
Of course its safe. Changing the brand wont effect anything. It's when you start changing the weight that your motor will be effected.
Title: Re: Mixing oils
Post by: LTZ C20 on June 30, 2016, 09:18:21 pm
Not necessarily true. You have to read the product info for each and make sure that the "mix in" oil you are planning on using has the same properties (ingredients) as the original oil you are using.

Some additives in your original oil which are there to benefit the engine could be "watered down" by the "mix in" oil. OR, the "mix in" oil could have properties which may benefit newer engines but counter act the properties of your original oil.

Always check to make sure they have the same properties and meet the same specifications.

For example, I was recommended by the manufacturer of my short block to use Rotella T 15w-40 Heavy Duty Diesel oil. Last time I did my oil change, I didn't have enough extra Rotella to do the oil change, so I used Mobil Delvac 1300 Super 15w-40 Heavy Duty Diesel oil which is what we carry in bulk at work because it is GM's recommended oil for the Duramax diesels. The two oils meet the same specifications and contained equal property. I will continue to use the Delvac instead because it's easily accessible and I can get it for cheap. But normally I use the rule: use what is recommended, not whatever is cheap and/or on hand OR pick one oil that meets your needs and stick with it. For me that's Mobil Delvac.

You should ask Vile what his opinion is on using various oils for your engine specifically. I would use what he recommended and nothing else.
Title: Re: Mixing oils
Post by: Stewart G Griffin on June 30, 2016, 10:12:05 pm
My opinion is that if you did it once or if it was a situation where you were a little low and the only thing available was a brand you normally don't use, you'll be ok.

i actually recently listened to one of Adam Carolla's podcasts which discussed specifically oil and mixing etc.:

http://tunein.com/radio/CarCast-Podcast-p345836/

i think you want the Jan 4, 2014 episode.   Only listen if you have time---it's long.
Title: Re: Mixing oils
Post by: philo_beddoe on June 30, 2016, 10:22:02 pm
I did some searching around, lots of results. A lot of folks saying its perfectly fine to mix brands, viscosity, etc.
Title: Re: Mixing oils
Post by: philo_beddoe on June 30, 2016, 10:28:40 pm
Just read the previous posts, hopefully VZ catches this, i'll wait to hear from him. I still have the first real oil change in there since the break in. Just reached 1k miles, the oil still looks like honey.
Title: Re: Mixing oils
Post by: Stewart G Griffin on July 01, 2016, 02:10:35 pm
Further thoughts:

1). Too much oil is better than not enough or no oil.

2). The wrong weight is better than not enough or no oil.

Title: Re: Mixing oils
Post by: VileZambonie on July 01, 2016, 06:10:27 pm
If you are using an oil that is incompatible with other oils for topping off etc then don't use that oil. I've made plenty of cocktails over the years and never had an issue. As far as too much oil is better than not enough, well maybe but to a very small extent.
Title: Re: Mixing oils
Post by: philo_beddoe on July 01, 2016, 06:12:16 pm
Still nothing solid regarding mixing brands and weights, all in the same pot. Not to mention a little synthetic in there too.
Title: Mixing oils
Post by: philo_beddoe on July 01, 2016, 06:13:12 pm
Whoops, typed too soon. Thanks.
Title: Mixing oils
Post by: philo_beddoe on July 01, 2016, 06:19:40 pm
I have about 2 cases of mixed brands, but all 10w40.

I just hate to waste it, i'll change my oil every 1k miles just to use it up. My engine will love it. Should be fine in the warm season.
Title: Re: Mixing oils
Post by: berserk on July 07, 2016, 01:13:47 am
The only way I would mix oil is if I was flat broke and the truck was reading a half quart or more low. But I also will ONLY run Brad Penn oil's in my k10 since break in,  I don't feel like the zinc additive is as good as the oil formulated from the manufacture with it already in there.
Not a lot of facts, just a lot of preference. 
Title: Re: Mixing oils
Post by: Blazin on July 07, 2016, 07:38:39 pm
I have mixed brands many many times over the years, Never had an issue.
Have mixed weights in my Jeep 4.0 before.
Title: Re: Mixing oils
Post by: Irish_Alley on July 07, 2016, 07:57:56 pm
i never had a issue with mixing brands. i cant say that ive mixed weights but then again i usually add a bottle of lucas or you hear of people adding trans fluid to their oil. i would think thats like stepping up and stepping down the weight of the oil.
Title: Re: Mixing oils
Post by: philo_beddoe on July 09, 2016, 10:41:50 pm
The new crate 350 engine calls for 10w30, is it ok to use 10w40 in the summer?
Title: Re: Mixing oils
Post by: LTZ C20 on July 10, 2016, 12:27:40 am
The new crate 350 engine calls for 10w30, is it ok to use 10w40 in the summer?
Don't change weights. It's designed for 10w30, use 10w30. We don't change all the weights of oil we use in customer's cars at the dealer depending on the seasons, use the same weight year round.
Title: Re: Mixing oils
Post by: Captain Swampy on July 10, 2016, 07:28:46 pm
Each oil manufacturer has their own blend of additives. When you mix brands, you run the risk of different additives not working well together. It probably wouldn't hurt anything, but I wouldn't do it in that new engine. Multi grade oils have viscosity index improvers and other additives. At risk of over simplifying it, 10w30 or 40 is a 10 weight oil with additives that give it the strength of a 30 or 40 weight oil. It flows easier and starts easier in the winter but the additives give it the film strength of the 30 or 40 weight oil. Some of you must remember when all we had was single grades, using 10 in winter and 30 in summer.

Anyhow, the first number is the flow rating for cold oil, the second for when it's hot. 5w20 and 5w40 both meet the cold oil specs for 5w . Newer engines have roller cams and don't need the zinc like flat tappet cams do. The zinc has pretty much been removed from oil because it didn't agree with catalytic converters. A high zinc oil would be beneficial in our engines and better than an additive, because the additive package is designed to work together.

Think of oil additives like an engine package. Dual quads with a stock cam and heads won't work well. It's all about the complete package.
Title: Re: Mixing oils
Post by: philo_beddoe on July 10, 2016, 07:47:54 pm
I did add the zddp addative, i got a couple cases of 10w40 for free. Until its gone, i'm changing every 1k miles. Then i swear, i'm off the stuff for good. Back to my usual max life 10w30 syn blend.  And 4 oz of lucas zddp.
Title: Re: Mixing oils
Post by: LTZ C20 on July 10, 2016, 08:44:27 pm
Or just not use the oil at all. It was free to you, so your not out any money. So recycle it or give it to someone who wants it. Changing the oil every 1K miles just to use up some free oil that doesn't match what you use is illogical, a waste of time and money because you have to buy a new filter every time you change it.

It really sounds like a waste of resources and energy just to use up some free stuff that you don't really need anyway. I wouldn't bother with the stuff, give it away or recycle it.
Title: Re: Mixing oils
Post by: Irish_Alley on July 10, 2016, 10:34:15 pm
could always just sell it. who knows what someone else needs or if its a good price they might just buy it anyway
Title: Re: Mixing oils
Post by: blazer74 on July 10, 2016, 11:57:25 pm
Like Richard Prior said about when he caught himself on fire. 

He had a little bit of whole milk, some acidophilus mixed together and when he dipped the Oreo Cookie in it blew up.

Definitely overthinking this.

Stay with the same type of oil and you'll be fine, don't mix multi viscosities with straight or conventional with synthetic or diesel oils.

If you have it use it if it fits manufacturers recommendations.  Every 1k is a bit extreme.

The starburst on the bottle is there for a reason. They all have to adhere to the particular designation.

Off the shelf conventional oil with the correct viscosity and some ZDDP for flat tappets and call it good.

There are synthetic blends out there that don't explode either.
Title: Re: Mixing oils
Post by: VileZambonie on July 11, 2016, 07:04:49 am
You can mix oil brands, types and viscosity. As long as they are compatible oils and meet the needs of your engine you have nothing to worry about. Don't overthink this.
Title: Re: Mixing oils
Post by: philo_beddoe on July 11, 2016, 06:51:27 pm
You can mix oil brands, types and viscosity. As long as they are compatible oils and meet the needs of your engine you have nothing to worry about. Don't overthink this.
Now thats the answer i wanted. For the others, i'll change every 3k and not waste resources.

Title: Re: Mixing oils
Post by: Stewart G Griffin on July 11, 2016, 09:29:52 pm
What brands are we talking about?
Title: Re: Mixing oils
Post by: philo_beddoe on July 11, 2016, 09:39:30 pm
Castrol, sunoco, valvoline and maybe quaker state.
Title: Re: Mixing oils
Post by: Stewart G Griffin on July 11, 2016, 09:57:52 pm
i dunno, i wouldn't worry too much about it.

How many miles you got on the new engine?
Title: Re: Mixing oils
Post by: philo_beddoe on July 12, 2016, 09:07:59 am
About 1k.
Title: Re: Mixing oils
Post by: Zaridar on July 17, 2016, 11:50:04 am
As long as the service rating ex. API  ASO or whatever meets the specs of you engine you can mix whatever you want.. Weight shouldn't matter unless u have a newer engine with VVT.   Too viscous "thick/heavy" will cause harder cranking and very slightly decreased mileage.. Too little viscosity "thin /light" might not have enough wear protection..     I generally stick with recommended weight unless really high miles on a non VVT engine maybe go a little "heavier"


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Title: Re: Mixing oils
Post by: Stewart G Griffin on July 17, 2016, 06:17:57 pm
How much zddp do you think you need?
Title: Re: Mixing oils
Post by: philo_beddoe on July 20, 2016, 12:42:31 pm
I believe its rich weyand who has a good write up on zddp applications. I think about 1200 ppm is good. If i'm wrong, somebody correct me.
Title: Re: Mixing oils
Post by: philo_beddoe on December 14, 2016, 10:25:28 pm
Just found this from HMM. Good write up.
http://www.agriculture.com/machinery/repair-maintenance/maintenance-minute-will-i-harm-my-engine-by-mixing-synthetic-oil-and