Opinions on Amsoil 10w-40 Synthetic High Performance

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Oct 30, 2003
Bakersfield, California U.S.A.
Looking for a 40 wt oil to put in my 383 stroker for the next oil change. Have 0w-30 GC in right now, but think a 40 wt might be a better option. Redline 5w-40 has been suggested, but I thought I'd ask what everybody's opinion is on the Amsoil 10w-40 Synthetic high performance. Temps never get below 30*F in the winter, and temps stay 85*-105* in the summer. I'm also having consumption issues with the GC. I'm not partial to one brand and I dont mind ordering it, although I'd prefer to find something OTC. Truck is driven every day, has a 6 qt. cap. and runs the stock tow package oil cooler on the side of the radiator.
I like the 10W-40 and am using here in frigid Wa. state in my wife's car. I don't think it's the best Amsoil for extended drains, but it's a good oil.

That said, why not use Amsoil 15W-40? I'm using it my car and cranks just fine even at 9°F. You would have zero climate issues in Cali with it. It's more HD than the 10W, it's cheaper and the viscosity spread is less.
Find a truckstop in Bakersfield that carries Delvac 1, 5w-40 and use that. It's very comparable to the two oils you mentioned, particularly the Amsoil formulation. Any of these will do very well ...
Just out of curiousity....if you're using the GC 0-30 right now and some are saying it's almost a 40 weight, then why would you say that you think a 40 weight would be a better choice???
I picked on this oil awhile back
but it's a really solid motor oil that takes a turbocharger or extreme heat/towing to beat it up .

I think it's a better choice than the Mobil 5/40 because it's a good bit lighter at 40c for use with the type lifters in this truck and about .8 cSt lighter at 100c off memory .

It should also help with your oil pressure if thats what you looking to improve .
The current 10w-40 formulation is 14.7 Cst @ 100C, with a HT/HS of 4.2 Cp, and a Noack of 6.6%.

In other words, it's almost identical to the 15w-40 in terms of high temp properties, but has marginally better low temp flow .... Since it meets ACEA A3, MB 229.3 and VW 502, I think it's better for gassers than the 15w-40, but who really knows.
From what all I have read on here, I understand 40 weight oils break down quick. Does this only reply to multi weights or dino oils?
Thats the Motorcycle oil

Heres the old mainstay the original " AMO " HP 10/40

vi @ 40c 79.2---- 22 lighter than Delvac 5/40
vi @ 100c 14.0
HT/HS 3.93
Noak 7.0
CCS 2614 @ -20

The vi @ 40c for the " AMF " M/C oil is 88.6 and CCS is 4500 @ -25c

Heres the Diesel Oil ;

Kinematic Viscosity @ 100°C, cSt

Kinematic Viscosity @ 40°C, cSt
100.2 -- pretty heavy like the Delvac 5/40

CCS Viscosity @ -20°C, cP

[ January 08, 2004, 07:00 PM: Message edited by: Motorbike ]
They have always been the exact same formulation ....

About 5%-10% of the stuff that comes off the bottling line is labelled "Motorcycle Oil". Take a look at the MSDS for these two formulations - they are exactly the same ....

The website rarely has up to date spec sheets posted ....
By the way, has anyone ever seen Motorbike and Terry Dyson in the same room at the same time...?

I know lots of USAF pilots from my active duty days, and most of them simply aren't this smart ....

Originally posted by TooSlick:
They have always been the exact same formulation ....

Then why did my VOA show the AMO to be exactly 14.0 @ 100c along with a different add pack than the AMF ?

The website rarely has up to date spec sheets posted ....

Go to the website , it's been up to date concerning these two oils for a year now .

Not giving you hard time at all , if I'm wrong though I'd like to know .

I'm always meeisg up the reply with quote deal

[ January 08, 2004, 07:08 PM: Message edited by: Motorbike ]
It's possible that the MC oil is now a different formulation, but I don't see any technical reason to make two different oils in this case, unless you wanted to add the borate ester back into the original 10w-40 formulation? The add pack for the 10w-40 and original 20w-50 racing oil were both changed in December of 1998. That was when they first went to the SJ/CH-4 chemistry, to make the stuff work better in hot running MC engines.

Since that time, there has been a ton of advertising from MC makers about the need for MC specific oils. That's when Amsoil started re-labelling some of their 10w-40/20w-50 as MC oil. I talked at length to an Amsoil Direct Jobber up at the 1998 Oshkosh Air Show about this and he was the one who told me what was going on.

If these oils really are different, the MC oil is the stuff to use in a HiPo application, since it has better high temp properties and is as thick as Delvac 1 ....If there is a VOA for the 10w-40, MC oil, I haven't see it? Show me the data and I'll believe you

The MSDS show the viscosity for both these oils to be 14.55 Cst for the latest batches tested. That's from October of last year ....Actually, all the physical properties data on the two MSDS is exactly the same.
I personnally would use the AMO . It will give quicker warm ups and better fuel mileage over the M/C oil and very good protection for you FI small block .

With that 6 quart sump you should be able to run the intervals on up if it's sealing , metering and firing well .

I'd run the oil till it's dark then... run it some more
Silverado ,

Tooslick still says this AMF Motorcycle oil is the same as the AMO over in the virgin analysis section even after I pointed Amsoils data sheet differences out along with actual additive pack differences in virgin AMF vs two UOA's of the AMO , one of them being his . I'd go look at that thread and if he's right I no longer recommend this oil for your truck as I was basing it on apparently an oil no longer offered based on the latest virgin analysis .

Amsoil should change the data if Tooslicks correct cause thats just not right .I would never personaly purchase an oil with typical data like the AMF for a car engine and neither would many others and they deserve to know ....

Try a group III 5/40 is what I recommend , it's less expensive to boot
I'm still very new to the whole oil scene, so what are some group III 5w-40's that would be worth trying. (and how do I find out what group an oil is part of) Preferably over the counter. So far the only one reccomneded is Delvac 1 5w-40..........but what others?
Again, I still dont mind ordering oil if its worth the effort. Not everybody orders "exotic" oils for their vehicles, so it would be a good discussion topic for the neighbors.

Originally posted by Silverado:
I'm still very new to the whole oil scene, so what are some group III 5w-40's that would be worth trying.

Rotella T 5w40, Valvoline Synpower 5w40, Castrol Syntec 5w40 (from Beligum, sold at VW dealers, might not be group 3 though, it could be PAO/ester)
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