5w-20 or 10w-30? Can you mix?

[MisterChrome]

I'm sure this comparison has been brought up before for which is best for cobras but my question was more about mixing. My car isn't due for a change yet (mileage and I looked at the oil) but the dipstick had it the middle of max and min but I wanted to add a quart since I heard the dipsticks are innacurate. Problem is I don't remember if I used 10w30 or 5w20 last time and I lost the sheet I wrote it on. I have some left over 10w30, so it might be that or for another one of my cars, and I just bought 5w20. They are both Mobil 1. Am I safe to add 10w30 even if I I might have 5w20 in it? Which should I stick to from now on?

 

[cobracide]

You will be fine, just don't overfill. In the middle of the marks is just great too. Best to change as soon as you can. Try and stick with a certain manufacturer and grade throughout the oil change interval. I stick with Amsoil and have mixed 0W, 5W and 10w no problem. Read up on oil, pao or group IV is what I run.

From UnleashedBeast:
Group II - Petroleum oil, commonly called conventional or dino oils
Group III - hydrocracked, or heavily refined pertroleum, has impurities
Group IV - PAO, man made synthetic, no impurities
Group V - diesters, some polarized, allows engine oil to stick like a magnet to metal

http://www.svtperformance.com/forum...yone-explain-base-stocks-me.html#post12148290

 

[MisterChrome]

I was going to change it yesterday but after draining a bit, I saw the oil was still very clean and new. Like I said, I'm messed up bc I lost the sheet where I wrote down mileage. So I guess I still have a little more to go. I do stick to mobil 1 just forgot which grade I used last...

 

[Tractionless1]

Yep it will be 7.5w/25. Next time you change ditch the Mobil 1 it's not a true synthetic.. Mobil sued to get their base stocks classified as synthetic. You're basically paying synthetic prices for semi-syn oil. If that's ok with you by all means continue using it as it's great oil. I'd rather get what I'm told I'm paying for.

Royal Purple and Amsoil are great. I've used both and sent Amsoil to be tested after 1200 miles and 1 yr. in the motor. Blackstone asked why I took it out as it tested as very close to "new." Of course I removed as it's common to do so if the oil has been in the car for a year. Their rebuttal was, "just the oil co's trying to sell more product."

 

[MisterChrome]

Yep it will be 7.5w/25. Next time you change ditch the Mobil 1 it's not a true synthetic.. Mobil sued to get their base stocks classified as synthetic. You're basically paying synthetic prices for semi-syn oil. If that's ok with you by all means continue using it as it's great oil. I'd rather get what I'm told I'm paying for.

Royal Purple and Amsoil are great. I've used both and sent Amsoil to be tested after 1200 miles and 1 yr. in the motor. Blackstone asked why I took it out as it tested as very close to "new." Of course I removed as it's common to do so if the oil has been in the car for a year. Their rebuttal was, "just the oil co's trying to sell more product."

What weight should I stick with?

 

[2DXTRM]

What weight should I stick with?

10W30.

You can even use Pennzoil or Quaker State synthetics.

 

[Tractionless1]

What weight should I stick with?

I use 5w-20, that's what he manual recommends. There's been talk before of owners using too heavy of a wt. and how it doesn't agree with these motors due to very tight clearances.

 

[MisterChrome]

10W30.

You can even use Pennzoil or Quaker State synthetics.

I'd probably stick to Royal

I use 5w-20, that's what he manual recommends. There's been talk before of owners using too heavy of a wt. and how it doesn't agree with these motors due to very tight clearances.

That is very true...and so the debate must continue...:banana: :shrug:

 

[Tractionless1]

I'd probably stick to Royal



That is very true...and so the debate must continue...:banana: :shrug:

Good choice, many happy owners here using RP. I'll post my data upon my next oil change with my current RP fill.

 

[01cobravortech]

In the process right now of getting a 15k sample on my Amsoil 10W-30 SS oil.

The fears about going to a different weight than Ford recommends...are just not substantiated. In fact, some of the brands that some folks use simply aren't as high quality as some think.

I've used Amsoil 0W-30 in the winter before and I'm strictly staying with their 10W-30. And the UOAs I continue to do on these long intervals between oil changes, show outstanding wear protection and they show that I can run their oil beyond ranges that most people wouldn't even dare to go to...out of unsubstantiated fear mongering from the 3k oil change crowd.

 

[racecougar]

I've used Amsoil 0W-30 in the winter before and I'm strictly staying with their 10W-30.

What steered you to the 10W-30 from the 0W-30? What was your cold idle oil pressure with the 0W-30? Cold idle pressures of 90-100 psi are pretty typical with 5W-XX oils, how high is it with the 10W-30?

 

[01cobravortech]

What steered you to the 10W-30 from the 0W-30? What was your cold idle oil pressure with the 0W-30? Cold idle pressures of 90-100 psi are pretty typical with 5W-XX oils, how high is it with the 10W-30?

There's a member on here...UnleashedBeast...who has dropped phenomenal knowledge on why Amsoil 10W-30ss is the way to go in temps above 32F. Sold me on it and I had subsequent UOAs to see what kind of wear protection my motor was seeing and how at long oil change intervals the oil didn't shear.

Unfortunately I haven't done any oil pressure testing with both oil weights. I rely on the UOAs to tell the story.

Feel free to PM UB (Troy). Great guy who will elaborate on so many things. Loves talking oil.

 

[racecougar]

Ah. Well, I'd just recommend taking it easy with the throttle until you're completely up to operating temp then. I'm sure the cold pressures of a 10W-XX oil are up there.

 

[cobracide]

Amsoil back a few years '07 where the group IV synthetic Signature was 0w-30. Then 10w-20 Signature was available in 2011. My last change in April, 5w-20 Signature finally went in.