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Picking a conventional 5w-20: sulfated ash, NOACK? #4536297
10/07/17 02:35 PM
10/07/17 02:35 PM
Joined: Oct 2005
Posts: 11,425
PA
d00df00d Offline OP
d00df00d  Offline OP
Joined: Oct 2005
Posts: 11,425
PA
Been using Castrol GTX 5w-20 in my 2011 RX-8. That's discontinued now, so it's time for something new!

For the US market, Mazda insists on a conventional 5w-20 that meets API SM with starburst. I know it can take a wider range of products, so I've been researching alternatives. But for now, I still have some time and miles on the engine warranty, so I want to stick with SN/GF-5 conventionals until it runs out.

At the same time, deposit control is a big deal for these engines. So, I'd prefer engine oils that are more likely than average to keep things clean. As I understand, sulfated ash is a decent proxy for deposit formation, and NOACK is an okay proxy for base oil quality. Someone please correct me if I'm wrong or missing anything. Either way, I figure cleanliness is a good thing to prioritize because API SN/ILSAC GF-5 will have other aspects covered beyond what Mazda originally specced anyway.

I've narrowed my list down to two options:

1. Mobil Super 5000 5w-20
2. Havoline 5w-20

Per PQIA testing (Mobil, Havoline), both have NOACK values under 13%, the lowest I've seen from big brand conventionals that still exist. However, only Havoline lists a sulfated ash number: 0.9% (source), which looks pretty good.

I also considered Pennzoil and Castrol GTX Ultraclean. Both make claims about cleanliness that are so strong that I'm tempted to take them into account. I'm just not sure how to weigh those marketing claims against their weaker NOACK numbers and unknown sulfated ash numbers.

As of now, I'm leaning toward Havoline just because it's the only big-brand conventional I've seen that shows decent NOACK and sulfated ash numbers -- other than Chevron Supreme, but that seems to be missing Chevron's "Deposit Shield Technology", which seems relevant.

Does that make sense? Any other factors or products I should consider?


2008 BMW M3
Re: Picking a conventional 5w-20: sulfated ash, NOACK? [Re: d00df00d] #4536309
10/07/17 02:49 PM
10/07/17 02:49 PM
Joined: Apr 2017
Posts: 426
Mississippi
Speak2Mountain Offline
Speak2Mountain  Offline
Joined: Apr 2017
Posts: 426
Mississippi
PYB 5w20

Re: Picking a conventional 5w-20: sulfated ash, NOACK? [Re: Speak2Mountain] #4536360
10/07/17 03:45 PM
10/07/17 03:45 PM
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d00df00d Offline OP
d00df00d  Offline OP
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Originally Posted By: Speak2Mountain
PYB 5w20

Already mentioned. Got anything to add about it?


2008 BMW M3
Re: Picking a conventional 5w-20: sulfated ash, NOACK? [Re: d00df00d] #4536365
10/07/17 04:01 PM
10/07/17 04:01 PM
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d00df00d Offline OP
d00df00d  Offline OP
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Another product I considered and rejected: Valvoline 5w-20 lists 0.8% sulfated ash, but PQIA found a NOACK of almost 15%. So I guess I'm assuming NOACK number that's lower by >2 percentage points is better than a sulfated ash number that's lower by 0.1 percentage points. Comments welcome.


2008 BMW M3
Re: Picking a conventional 5w-20: sulfated ash, NOACK? [Re: d00df00d] #4536417
10/07/17 05:28 PM
10/07/17 05:28 PM
Joined: Jun 2012
Posts: 1,763
USA
oldhp Online content
oldhp  Online Content
Joined: Jun 2012
Posts: 1,763
USA
How about using Castrol Superclean GTX 5W20?


2018 RAM 1500 3.6/8 speed.
2017 Jeep Sahara Unlimited 3.6
"U kan't fixe it......if'n it ain't broke."
Re: Picking a conventional 5w-20: sulfated ash, NOACK? [Re: d00df00d] #4539746
10/11/17 12:10 AM
10/11/17 12:10 AM
Joined: Jul 2016
Posts: 204
Albury, NSW
JFAllen Offline
JFAllen  Offline
Joined: Jul 2016
Posts: 204
Albury, NSW
You can't even buy a XW20 Mineral oil in Australia. must lads here run synthetic 30 or 40W oils.

Re: Picking a conventional 5w-20: sulfated ash, NOACK? [Re: d00df00d] #4576092
11/16/17 01:27 PM
11/16/17 01:27 PM
Joined: Apr 2015
Posts: 289
Georgia
Charlie2015 Offline
Charlie2015  Offline
Joined: Apr 2015
Posts: 289
Georgia
Any name brand conventional oil will work fine. All the brands you have mentioned are good. Just keep the oil level full. I'm a valvoline guy, but I hardly ever use the conventional. If I had your RX-8, I would continue with Castrol. The engine will need to be rebuilt after a certain interval no matter how much thought and effort you put into picking the "perfect" oil. You already know Castrol makes a good product, and the new GTX Ultraclean is an improvement to keep up with new automotive technologies and certifications.


1998 Honda Accord EX 2.3L Auto (Sold) 214k mi
2009 Scion tC Manual (Daily Driver) 165k mi
Re: Picking a conventional 5w-20: sulfated ash, NOACK? [Re: d00df00d] #4576298
11/16/17 04:43 PM
11/16/17 04:43 PM
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Posts: 11,425
PA
d00df00d Offline OP
d00df00d  Offline OP
Joined: Oct 2005
Posts: 11,425
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Ha, had forgotten about this thread.

Ended up going with Mobil Super 5W-20. It's what the shop used when they installed the engine (I think), and it's one of the cheaper options to boot.

Guess I hadn't realized this when I first posted, but GTX Ultraclean 5W-20 is a synthetic blend. Doesn't bother me, but it's technically against Mazda's guidelines and I don't want to stray until after the warranty ends.


2008 BMW M3
Re: Picking a conventional 5w-20: sulfated ash, NOACK? [Re: d00df00d] #4577098
11/17/17 01:08 PM
11/17/17 01:08 PM
Joined: Jun 2017
Posts: 619
DFW
JustN89 Offline
JustN89  Offline
Joined: Jun 2017
Posts: 619
DFW
I've always been a big fan of conventional Pennzoil. I don't know why, but while I'm not brand loyal with synthetics, I'm fiercely loyal to PYB if I want to run a synthetic.


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