Say you mix 3 quarts of 5W30 and 10W30 what do you get? 7.5W30? Will the two just seperate out from each other like oil and water?

Is this safe to mix or run? I dont plan doing it I was just wondering this today.....

 

regulations require that all typical motor oils have to be compatible and can be mixed together........including dino and synthetic.

but that doesnt mean it will work optimally.

 

just buy syn blend oil

 

absolutely no problem with that at all.

I still wouldn't mix syn and dino oil though. you'll be losing the benefits of the syn.

 

Mixing two weights of oil does not equal out to the viscosity you think it would. Often times one viscosity of an oil contains a different amount of viscosity index improvers, so mixing it with a different viscosity will have different reactions. Plus an oil that is rated 5w30 can have a varied viscosity as it is, because the range of a 30wt oil is 9.3 cst to 12.5 cst at 100c. Some oils, like Mobil 1, are on the low end of that range, while others like Amsoil or Redline, are on the high end.

The first number in the oil is actually not even a viscosity, it's just an arbitrary number which shows that it passed a certain cold cranking test. For example, to be a 5w oil, it must have a cold cranking number of less than 6000CP at -30c. When you take a thicker oil like 15w50 and mix it with 5w30, chances are very good that it will no longer qualify as a 5w oil anymore, so it moves up to the next level of 10w (which to qualify for that, you need to have a cc number of less than 6000CP at -25c)

The best thing to do if you're mixing oils is to have an oil analysis done on it, so see what it's actual viscosity at 40c and 100c is, that way you can get an approximate idea of what it's new rating will be. A typical 5w30 oil like Mobil 1 has a viscosity of around 50-53cst at 40c, and around 9.7cst at 100c. A typical 10w30 oil is around 60-63cst at 40c, and 9.8cst at 100c.

If you truly want to go with a slightly thicker oil, instead of using Mobil 1, go with something like Amsoil or Redline. Or if you're dead set on M1, try out their 0w40.

I've been doing a lot of oil analysis lately on all my cars in my family, and trying to figure out what viscosities and what oils work best for me. I have a strong feeling that the LT1, especially one with higher mileage, likes an oil thicker than Mobil 1 5w30 and 10w30. Something closer to the high end of a 30wt, or even something on the low end of the 40wt might work best for the lowest possible engine wear.

There is also a new player on the market, Castrol has an oil in Europe called Formula SLX 0w30, which is now being sold in North America under the Syntec label. On the back of the label it says made in Germany, if it doesn't say this, it's the US made stuff which is not the same. This oil has a pour point of -81F, but is also thicker than most 30wt oils, it's almost a 40wt oil (it's 12.1cst at 100c which is only 0.4cst from being a 40wt) I'm getting back a 5500 mile oil analysis on this stuff in my sister's car this week actually, so we'll see how it performed. In Canada this oil is only available at Walmart so far, in the US it's only been spotted at a few Autozones so far.

 

Patman,

What oil do you recomend for an LT1 with about 80000 on the clock? I've been running the Valvoline Maxlife, but I wonder if I need to be runing a synthetic.

 

I ran Maxlife in my Firebird last year and wasn't super impressed with the oil analysis results actually.

Right now I'm running Schaeffer Oil 5w30 blend in my Firebird, with 87k on the clock.

There are a lot of good synthetics you could try out, my preference would be towards Redline or Amsoil, and if the new German made Syntec 0w30 works out, I'll start recommending that too, but I want to wait for oil analysis results first.

There is no reason to avoid synthetics on a higher mileage engine, although I would avoid Mobil 1 5w30 and 10w30 simply because they are too thin for the best engine protection.

 

I used Amsoil, M1 and every other kind of synthetic. But the best I have come across, as far as protection, and good oil lab results has been Havoline 10-30.

I have a sample ran every oil change from Blackstone Labs, and that has been the best so far. M1, actually showed wear in my V6.

So, I am sticking w/ good ol' Havoline. And I think 10-40 is great for high mileage LT1s, just like someone mentioned

 

If you don't mind, could you share some of those oil analysis results on this website below:

http://theoildrop.server101.com/cgi/...ne=5&submit=Go

 

What if you mixed green and orange coolant?? any harm??

 

now that on the other hand would be just stupid

 

My buddy did it and his water pump blew out!!!
You could barely recognize it afterwards..

I told him!!!

 

I will have to go find all my Blackstone Lab reports. And that will be the hard part. Let me do some looking around the house. Blackstone will not say which oil is better, I just got MUCH better results w/ regular Havoline 10-30 in my Z, than the M1 that has been ran in my 95 3.4 V6. The V6 has 59k and the Z has 86k.

 

You cannot directly compare those reports like that though. Different engines will show different levels of wear.

In order to truly see if one oil is better than another, you need to run it in the same engine, under identical driving conditions.