Rate these conventionals in order.

[MGregoir]

Castrol GTX
Quaker State
Pennzoil
Mobil Clean 5000
Havoline DS
Valvoline All-Climate

Add a particular favorite if you have one but these are the main brands I tend to see mentioned as "upper tier" straight conventionals (rather than say Chevron Supreme, Exxon Superflo, FormulaShell, etc.). PCMO rather than HDEO.

 

[Camu Mahubah]

If I were walking down the oil aisle and these oils you have listed were the choices I would check the price of the Valvoline first as I have used Valvoline all my life and really enjoy the smell of it plus it lubricates my engine very well. If Valvoline weren't on sale I'd use Pennzoil. Next would come Mobil then Quaker State. Havoline then Castrol GTX. And that is acutally how it would occur in my head. No rationality behind it just my picks. Although my last choice, Castrol would be chosen over the others if it were cheapest.

Valvoline(used it all my life no lubrication issues)
Pennzoil(stellar UOA's)
Mobil Clean 5000(who can resist extending a 3000 oci a bit more)
Quaker State(I hear it's good oil but it's not Pennzoil even though it's owned by Sopus. I believe Pennzoil gets more R&D and this is their value oil.)
Havoline DS(Near the bottom because I hear it's thinner than others at operating temp.)
Castrol GTX(I like cold weather specs and this one might be a bit lacking)

Despite anything I have said I would buy the best priced oil. All are good. It's just a matter of opinion if one thinks one SM conventional is better than another. Save money and if your brand happens to be on sale, HOORAH!

 

[aquariuscsm]

Valvoline all the way!

 

[goodvibes]

My motors always run smoother, quiet and free on Valvoline. With current SM ratings, I wouldn't worry about any of these so if it feels better, why not?

 

[bobfather99]

All fine oils, Id go with the lowest price.

Lately Ive been using QS, from the recent Autozone special..

 

[twentynine]

Look at the thread titled Rate These Synthetics for my answer and then change the relavent words to read conventionals.