Mixing oils

[LTZ C20]

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.

[Captain Swampy]

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.

[philo_beddoe]

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.

[LTZ C20]

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.

[Irish_Alley]

could always just sell it. who knows what someone else needs or if its a good price they might just buy it anyway

[blazer74]

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.

[VileZambonie]

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.

[philo_beddoe]

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.

[Stewart G Griffin]

What brands are we talking about?

[philo_beddoe]

Castrol, sunoco, valvoline and maybe quaker state.

[Stewart G Griffin]

i dunno, i wouldn't worry too much about it.

How many miles you got on the new engine?

[philo_beddoe]

About 1k.

[Zaridar]

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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[Stewart G Griffin]

How much zddp do you think you need?

[philo_beddoe]

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.