"Mixing of oils"

[Desert_Nomad]

Greetings,
Got a question, mabey a crazy one at that, but can I mix 10w30 with 20w-50 in an effort to get a viscosity of somewhere near 15w40? Both oils from the same manufacture. The reason I ask is that my '67' big block 427 has always liked the 10w-40 mix. The Valvoline VR1 oils are readily available in my area, are cheaper than those speciality oils, but don't come in that grade. I think 20w-50 may be a little to thick especially for cold starts. Thanks.
Desert Nomad

 

[aquariuscsm]

Imo,the VR1 20W50 would be perfect in that engine,especially in a hot/warm climate. Is your engine modded out,and do you race?

 

[znode]

Without your own oil lab, not reliably so. I mean, you can mix up different samples and send them off to Blackstone, but 10W- or 15w40 isn't exactly rare or expensive. Cheap HDEOs always come in that grade. Grab some Shell Rotella or Chevron Delo and be done with it.

 

[Desert_Nomad]

Thanks for the reply. The car is a stock 427/390hp Corvette. I don't race as its a restored Classic. It has about 2000 miles since rebuild. I've been running Valvoline 10-40 since birth, but with drop in zinc I'm trying to protect the engine and at the same time stay with in the same viscosity. I was also thinking 20w-50 would be 'ok', just worried about cold starts as thats where a lot of the wear comes from. I figure 10w30 would be just a little to lite in this climate.
Desert Nomad

 

[addyguy]

Chev BB's in geeral like thick oil, or so I've read many, many times. GM even recommends 20W-50 in their HP crate engines.

I'd run 20W-50 in that beast w/o a second thought. VR-1 would be a good one to use.

BTW, sounds like a REALLY nice car!

 

[Desert_Nomad]

Thanks again for the replies. As summer is coming, I guess I'll stick with the VR1 20w-50. These BB do get hot and I'm sure the 50w won't hurt once up to running temp. I may revert back to a 10w30 during winter but we'll see. Thanks again.
Desert Nomad

 

[znode]

I don't know anything about BB's, but I do know something about southern California - our "cold starts" are NOT cold starts. 20W's can crank at 14F - and Torrance hasn't dropped below 30F in the last 3 years, am I right?

 

[Desert_Nomad]

znode,
Your right on the temp's, I have never seen nothing less than 35F around here. I guess I'm a bit overprotective. Got to much money invested in it. Just want to treat it right.

 

[exranger06]

I also have a 67 Corvette 427 BB. I use Mobil 1 15w-50 in it.

 

[Jaymus]

An HDEO 5W-40 would be on the thick side of the 40 weight range and have around 400ppm more zinc/phosphorous each than your average PCMO like Pennzoil Yellow Bottle or Castrol GTX. That's what I would run, but people on here mix oils all the time with no problems.

 

[Desert_Nomad]

I know a few that do use synthetic's in their mid-years, and I agree its a superior oil to dyno. Most of the guys I've talked to on the forum(Corvette) tend to stick with the conventional oil on cars like this due to how much they run them, and that a lot of these cars sit in the garage for a good portion of the year. Also, I guess the economics of it.

 

[Wilhelm_D]

Originally Posted By: Desert_Nomad
The car is a stock 427/390hp Corvette. I don't race as its a restored Classic. It has about 2000 miles since rebuild. I've been running Valvoline 10-40 since birth, but with drop in zinc I'm trying to protect the engine and at the same time stay with in the same viscosity. I was also thinking 20w-50 would be 'ok', just worried about cold starts as thats where a lot of the wear comes from. I figure 10w30 would be just a little to lite in this climate.


There are lots of ways to solve the problem if you want a high ZDDP 10W-40.

There are lots of 10W-40 motorcycle oils with high ZDDP levels.

For a quick example you could mix Mobil 1 MX4T 10W-40 which has 1200/1300 ppm of phosphorus with just about any other 10W-40 motor oil 50/50 and wind up with something around 900/1000 ppm of phosphorus, about where the oils were before they started dropping the ZDDP levels.

 

[Steve S]

Originally Posted By: Desert_Nomad
Greetings,
Got a question, mabey a crazy one at that, but can I mix 10w30 with 20w-50 in an effort to get a viscosity of somewhere near 15w40? Both oils from the same manufacture. The reason I ask is that my '67' big block 427 has always liked the 10w-40 mix. The Valvoline VR1 oils are readily available in my area, are cheaper than those speciality oils, but don't come in that grade. I think 20w-50 may be a little to thick especially for cold starts. Thanks.
Desert Nomad
Cold starts in Torrance? 20w is just guessing good to below 32*f starting . Where do you get the too thick for cold starts? 15w40 and 20w-50 seems fine for big block Chevies. You won't find any better oils than the 15w40 HDEOS Delo 400 or Shell rotella ,Mobil Delvac 1300 etc. I have run 15w40 and 20w-50 is my big block Chevie engines in my lake boats and they are 7,500 RPM engines and look real good upon tear down. You do not need syn in your engine unless yot road race the engine as you can't run the engine hard enough on the street . If you towed a real heavy trailor then maybe syn oil.

 

[Steve S]

Where cold start wear comes into play is when for example you run a straight 30wt and try to start the car when it is 0*f .the engine runs without oil because the oil won't get to the pump.

 

[Audi Junkie]

Just use 15w40.

 

[Audi Junkie]

Originally Posted By: Steve S
Where cold start wear comes into play is when for example you run a straight 30wt and try to start the car when it is 0*f .the engine runs without oil because the oil won't get to the pump.


SAE 30 is about the same as 15w40 at near sub freezing.

 

[Jaymus]

But how much more is the cost of an HDEO 5W-40 vs whatever conventional oil you are going to choose? Because HDEO oils are dirt cheap. Rotella-T Syn 5W-40 is, or was, $19 at Wal-Mart. $19.99 at Autozone.

Not trying to force it on you, but just looking at it from both sides. I have an 86 F-150 5.0 EFI that had 109k miles when I got it nearly 3 years ago. Now at 128k miles, it's had the last 10k-12k ran on RTS 5W-40. No leaks have occurred and oil consumption went down from conventional 10w30.

 

[addyguy]

When you have a BB Corvette, I don't think the cost of the oil should even be a consideration.....

 

[Captain_Klink]

basically it should work well. synthetic 10w30 has excellent cold properties, and should thin out the 20w50 nicely. if you mix half and half, you will get pretty close to 15w40.

 

[Jaymus]

Originally Posted By: addyguy
When you have a BB Corvette, I don't think the cost of the oil should even be a consideration.....


If that was directed at me, I was responding to him saying he wanting to be economical because he does short OCI's. I was just pointing out the fact that HDEO's are cheap. And would protect this engine.

But if the others on here feel a 20W-50 is what's best for it... then go for it. I just know HDEO's are on the thick side of the scale, too, on viscosity. And if he does short changes, he'll be running a thinner start up oil that will protect against fuel dilution better at the same time. HDEO's are just plain stout.