Using 5W-30 In Engine Specified for 10W-30

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Engine: Buick 3800 series II V6. Current Oil: Chevron Supreme 10W-30 SL at 5 quarts. What would happen if I switched? Why do we need 10W-30 when there is 5W-30 available? For some unknown reason, the engine seems to run quieter when it's hot; about 195F and above. Also I noticed that when looking at product data sheets, these two grades are similar in cSt numbers. Often times a 5w30 has a slightly higher cSt number at 100C. For example: 10.6 cSt as opposed to 10.0 cSt. It seems as though an increasing number of owners with vehicles produced after 1990, are using 5w30; why do you suppose that is? My oil next OCI is comming up in April, and I'm wondering if I should switch over. Your opinions please. [Patriot] [ March 25, 2006, 03:32 AM: Message edited by: GoldenRod ]
 
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My Rodeo calls for 10w-30 at temps above 0F, and to only use 5w-30 if below 0F temps are encountered and/or cold starting is an issue. But, in general, this engine specs anything from 5w-30 to 20w-50. I'd ran 10w-30 Havoline dino solid for 147k miles; decided to get a funny hair and tried a 5w-40; and then even a round of Havoline Blend 5w-30. I didn't notice any difference, with the exception that the truck really did like the Havoline blend 5w-30; however, I only ran that oil through our coldest months. I did a UOA on it, results were great. However, I have no means of attempting it through summer as Havoline blend is being pulled off the shelves, and my truck does not like (gets pretty noisey) on Havoline regular 5w-30. Switching the truck back to Rotella synthetic 5w-40 yr round. I wouldn't truly want to run a 5w-30 in the summer months in an engine spec'd for either, and ONLY because the 5w-30's tend to shear faster leaving more residue behind. Otherwise there's no difference between running either one, except the 5w-30 gets to the top faster.
 
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If you're comfortable the additional VII polymers in 5W-30 will handle the heat of summer driving (the latest ones are more shear and oxidation stable than previously), go ahead. Apparently GM felt it had reason to err on the side of caution, though. In a moderate climate (consistently above freezing), I doubt 5W-30 gets to the top end faster than 10w-30. Having said all that, my battle cry is still, "They'll have to pry my 10W-30 out of my cold, dead fingers!"
 
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More recently, 5w-30 is spec'd for all temperatures in the 3800 V6. They haven't significantly changed the engine, either. I'd say go for it.
 
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Colorado Springs
Like Ray, I'm a die hard 10w-30 'believer". However, after my -15F 10w-30 starting issues, all vehicles I service are now on 5w-30 Trop Artic. My moms 3800 Olds 88 runs much smoother on the 5w-30 in colder weather. If it never gets bitterly cold though, I doubt you'll gain anything nor lose anything by going 5w-30. Maybe, go to the auto parts store with a blindfold? I've been having to do that lately...**** BITOG got my mind all messed up
 
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Buffalo, NY
quote:
Originally posted by GoldenRod: Engine: Buick 3800 series II V6. Current Oil: Chevron Supreme 10W-30 SL at 5 quarts. What would happen if I switched? Why do we need 10W-30 when there is 5W-30 available? For some unknown reason, the engine seems to run quieter when it's hot; about 195F and above. Also I noticed that when looking at product data sheets, these two grades are similar in cSt numbers. Often times a 5w30 has a slightly higher cSt number at 100C. For example: 10.6 cSt as opposed to 10.0 cSt. It seems as though an increasing number of owners with vehicles produced after 1990, are using 5w30; why do you suppose that is? My oil next OCI is comming up in April, and I'm wondering if I should switch over. Your opinions please. [Patriot]
Interesting. My 1990 version of the same engine calls for 5W-30 as the "preferred" oil, and 10W-30 as an option "above 0-degrees." Yet, my sister's 2002 vintage 3800-engine calls for 10W-30 as the preferred oil... I'm not sure, but I think there may have been some oil-consumption issues with 3800s and 5W-30 in the early 90's. That's just a theory, but one based on some evidence while changing oil at that time... (we had a lawyer that drove a Pontiac Bonni. that would eat quarts of oil, right out of the box. I think he forced the dealership to take her back as a lemon, or at least got a new motor.) In any case, I can't imagine that 5W-30 would be a problem at least in the colder months, but I'd stick with 10W-30 for spring-fall if it were mine.
 
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I think you'd be fine with 5W-30. API SM/ILSAC GF-4 5W-30s are far better than the 5W-30s they used to be worried about when they spec'd 10W-30 for that engine. I used to be a 10W-30 summer user, but since 5W-30 costs the same and passes the same modern engine tests as 10W-30, I just use 5W-30 for summer now.
 
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Look, 5w is too thick when you start up. 10w is too thick when you start up. 5w is better at startup than a 10 weight, and the 5w (generally) will continue to be flowing better until you reach operating temps. THEN, assuming they are both Xw-30 weights, they will flow about the same. (Yes, there are exceptions. Yes, Mobil 1 seems to be thinner, and Castrol German Green 0w-30 is an anomolie.) So what? Well, if you believe that the majority of engine wear occurs at startup due to no/inadequate flow, and increased rates of wear are still occuring before reaching full operating temperature, the new 5w-30 is a no-brainer...it's better than the 10w-30 of old days. If you don't believe that line of thinking, then, maybe getting a voodoo doll to put in a miniature vehicle like yours and do some sort of "make it better, make it better" chant will make the 10w-30 better?! [Happy]
 

GoldenRod

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So then would you guys say that a Group 3 synthetic like 5W-30 PP would perform as well, and be as safe to use, as a top brand dino 10W-30?
 
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Goldenstaff asked: So then would you guys say that a Group 3 synthetic like 5W-30 PP would perform as well, and be as safe to use, as a top brand dino 10W-30? No, I wouldn't. [No no] I would say 5w-30 dino will protect BETTER than 10w30 dino in a car that has cold starts as part of it's normal routine. In an engine that rarely gets shut down, 10-30 dino would be about equal to 5-30 dino. The newest 5-30's just don't have the shearing problem of the older ones, that's why the old 10-30's MAY have been better than some of the old 5-30's...although I'm not convinced that is a fact...I think the old 5-30's that were shearing to a 5-20 pretty fast were perhaps doing the engine a favor, as it is obviously evident by today's UOA's and engine longevity on the modern 5-20's are very, very good. However, back to your question: PP 5-30 is even better than dino!
 

GoldenRod

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Mr. Titan: After reading your post about 10 times it finally made perfect sense. I think you may have cured me of my 5W-30 fear. [Smile] 777: PP is Group 5? Really? [Eek!]
 
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Guys, I haven't been watching UOAs like I was a year or more ago, but I concluded then that most conventional 10W-30s were shearing down about as fast as 5W-30. So, unless you have an oil that's known to be exceptionally shear stable (like Schaeffer), I don't think it matters much to use a 5W-30 in an engine asking for 10W-30. I do like a 5W-30 in just about every application involving cool/cold starts, however. Years ago, I would have preferred 10W-30's shear stability ... but I think that difference has just about disappeared. [I dont know] --- Bror Jace
 
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Wisconsin
At temperatures above 50 degrees F, very little difference exists between the performance of a 5W-30 & a 10W-30. A 5W-30 will generate better fuel economy in short trip situations, during the initial 5 minutes of operation. As Bror indicates, both products will shear, primarily due to the use of VI improvers to pass the GF-4 fuel economy test. The uncoiled VI improvers will become straight, under pressure, and generate a temporary reduction in viscosity. This is all that's needed to beat the PAO reference oil by 1.5-2.5% in fuel economy. Just my IMHO, of course! [Smile]
 
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EOPs have also been unofficially spoken of as "super-Group IIIs"*. I'm not at all certain the API has actually faced the nomenclature delemma on these GTL fluids, yet. *GTL fluids defy easy pigeon-holing - they're polymerized (built-up) starting with methane gas, not isomerized (molecularly re-ordered) from complex molecules, and contain no unstable sulfur and nitrogen containing, or unstable solvent-like double bond, ringed polycyclic aromatic structures. On that basis, they could be defined as a sub-class of the Group IV designation. If "Group V" effectively becomes the trash can designation for future base oil technology, it loses all meaningfulness. [ March 26, 2006, 01:01 PM: Message edited by: Ray H ]
 
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I don't think the EOP used in PP should be called a GTL oil in the sense of Fischer Tropsch because it isn't. It's no more a GTL than POA is.
 
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In my reading of the spec sheets for most major brand dino oils, the differences between 5w30 and 10w30 are minimal. I'm sure this has to do with making 5w30 able to stand up to operating conditions and making 10w30 still able to meet the EC spec. In my experience with my Mazda, Exxon Superflo is especially cold weather friendly in the 10w30 grade. My car sees lots of cold starts and short trips, so I can tell a difference in city mileage when using 5w30, but i do feel better using 10w30 in the Texas summer, although the dealer uses 5w30 year-round.
 
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