Compelling reason to switch to a 5w40 oil?

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816
Location
McGregor TX
I have a Pontiac Trans Sport with the 3.4L v6. I have heard that this engine "likes" 40 weight oils. However, I've always used 30 weight oils. I used a good 10W30 dino up until around 50K miles and have used AMSOIL (both 10W30 and now 5W30) since then. I now have over 80K miles on the vehicle. There is no noticeable consumption between oil changes and I usually drain at around 6000-7000 miles, which comes to about 6 months for me. My question is this: if my engine does not use oil, and seems to be running fine, is there any compelling reason to switch to a 5W40 oil like the new Mobil SUV or the new AMSOIL 5W40? I know I could take a baseline UOA and then switch to 5W40 and compare, but I'm concerned about going back and forth between a 30 and 40 weight oil. If you go to a heavier oil is there any chance that going back to a lighter oil would damage the engine or caused increased oil consumption? David
 
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4,872
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MN
I don't see why a Xw30 wouldn't be just fine. Check for UOAs on 3.1s and 3.4s. I don't see why it would "like" 40w. -T
 

Patman

Staff member
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22,011
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Guelph, Ontario
You could always just go with something that is a thick 30wt instead. Something like Amsoil 5w30, which starts out at a very high 30wt and often thickens up to a low 40wt.
 

mrdctaylor

Thread starter
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816
Location
McGregor TX
Hmmm. I actually have been using AMSOIL 5W30 for my last couple of changes. I guess this or AMSOIL's 10W30 are good oils for this engine. I guess I was thinking that it would be nice to use something like Mobil 1 that is available locally. I know their 30W oils are on the thin side so I was kinda thinking their 5W40 might be a good choice. I dunno.
 
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2,768
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Tn
My 2 cents. Stay with the Amsoil, but if you want Mobil the 10W-30 is fine. I would not even consider a 40 wt. More viscosity is not needed, imho.
 
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71
Location
Windsor, Ontario
Patman is BANG ON! The Amsoil ASL and ATM products start out high in the 30wt range and if you leave them in for 6 to 12 months time, they will thicken into the 40 wt range. I have experienced this 1st hand in my 02 Jeep with the ATM and in my 01 Neon with the 0W-30 product. I don't see any need to change from what you are currently doing. [Cheers!]
 

mrdctaylor

Thread starter
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816
Location
McGregor TX
Hmmm. This begs the question: How different ARE the viscosities within 30W oils. If Mobil 1 is on the low end and AMSOIL is on the high end, how much difference is there REALLY? I've heard some stories on here from people who switched to Mobil 1 and got more noise in their engines (presumably due to it being thinner) and switched to something thicker like AMSOIL or GC. Basically, I've used Mobil 1 on my Toyota since I've bought it and (obviously) everything works great. At the time I was already using AMSOIL on my van and stuck with it. Now that I've used up my stock of AMSOIL I'm trying to decide whether to keep spending the bucks on it or switch to Mobil 1 which I can get for $20/5 qts at Wally World. My van has about about 82K miles, and have been using AMSOIL synth since around 50K. I guess I'm just concerned about going to a thinner 30W oil. This is probably not as big of a deal as I'm trying to make it, really, which is the reason for my question above. David
 
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2,622
Location
MN
I have been using M1 5w30 in my Transport and it hasn't come flying apart yet, so I don't see a need for a 40W oil. I have been running M1 5w30 year round for about 55,000 miles and it seems to work good. I might try 10w30 this summer but I don't think there is anything to be gained.
 

Patman

Staff member
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22,011
Location
Guelph, Ontario
quote:
Originally posted by mrdctaylor: Hmmm. This begs the question: How different ARE the viscosities within 30W oils. If Mobil 1 is on the low end and AMSOIL is on the high end, how much difference is there REALLY?
I saw a pretty significant reduction in lead in my UOAs in both of my cars when switching from a low end 30wt to a high end 30wt. More than 4 times lower lead!
 
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College Dorm...
quote:
Originally posted by Patman:
quote:
Originally posted by mrdctaylor: Hmmm. This begs the question: How different ARE the viscosities within 30W oils. If Mobil 1 is on the low end and AMSOIL is on the high end, how much difference is there REALLY?
I saw a pretty significant reduction in lead in my UOAs in both of my cars when switching from a low end 30wt to a high end 30wt. More than 4 times lower lead!

Have you tried a 5w-40 yet?
 
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2,768
Location
Tn
Yep, Wally's price on M1 10W-30 is attractive. [Big Grin] I got a good uoa with it. I'm going to try ATM 10W-30 later, though. I think it's more of what oci your trying to achieve and any consumption issues that would affect overall costs. I think either is fine. I see no compelling reason to go with a 40.
 

Patman

Staff member
Messages
22,011
Location
Guelph, Ontario
quote:
Originally posted by Jelly:
quote:
Originally posted by Patman:
quote:
Originally posted by mrdctaylor: Hmmm. This begs the question: How different ARE the viscosities within 30W oils. If Mobil 1 is on the low end and AMSOIL is on the high end, how much difference is there REALLY?
I saw a pretty significant reduction in lead in my UOAs in both of my cars when switching from a low end 30wt to a high end 30wt. More than 4 times lower lead!

Have you tried a 5w-40 yet?

Not yet, but the Syntec 5w40 or Mobil 1 0w40 would be oils I would probably try if GC goes away. But honestly, my results are so impressive with GC (and it's the cheapest full synthetic up here) that I won't switch until I can't get the oil anymore.
 
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3,704
Location
Chattanooga, TN
My question is this: if my engine does not use oil, and seems to be running fine, is there any compelling reason to switch to a 5W40 oil like the new Mobil SUV or the new AMSOIL 5W40? If it ain't broke don't try to fix it. I used the Amsoil 10W30 for 12 years on my Camry (160,000) and I only recently switched to Schaeffer 15W40 to see if I could reduce minor consumption and some seal seepage. So, far looking good Could a different weight do a better job or increase longevity, maybe, maybe not, you will never know so if the engine is operating fine I would suggest just leaving the oil the same.
 
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296
Location
Eldora, Colorado 9000'
The only difference you may see is in gas mileage. I doubt engine life will be effected at all by 5W40 over 10W40, especially with such good synthetics. I run 5W40 M1 SUV (Delvac 1) since it's so hot here in S. Arizona. My oil gets abused!
 
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