5W-20 in place of 5W-30.

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I am sure this one has been debated before, and I'm kind of curious about it but I was just thinking about the characteristics of two different oils. Would a thick 20 weight, say 9.1 cSt at 100 degrees, with a HT/HS of 2.7, that stays in grade offer significantly less protection than a 5W-30 with a viscosity of 9.7 cSt at 100 degrees and an HT/HS of 2.9 or 3. I know that most 5W-20s have a pretty beefy additive package if they are Ford/Honda approved, and I am wondering if a 9.1 cSt 5W-20 is really that much different than a 9.7 cSt 5W-30 if both hold their grade, which is the next question. I will have to read some UOAs. The application would be in a 1999 Malibu V6 with the 3100 low output (155 horsepower versus the later in model year 170 horsepower update) engine. Primarily lots of cold start, 15-20 minute runs, with the occasional long highway drive. It doesn't normally see heavy loads, extended high RPM running, or extremely high temperatures. I would imagine the oil temperature takes a significant amount of time to get to the point where it would be much thinner than the 5W-30. The "most severe" duty the engine would see, temperature wise for the oil, is probably a sustained RPM run at 80 mph with the air conditioning on full on an 85 degree day, and the only time the temperature really comes up is on the highway at higher speeds on a hot day, and sitting parked in city traffic. It very seldom sees enough runtime to get the oil temperatures up significantly in the stop-and-go situation. The change intervals are short, typically no longer than 3500 miles, so the oil would have life in it as it came out of the engine. The two oils in question are Castrol GTX 5W-20, and Havoline DS 5W-30. The 5W-30 is on the thin side but Chevron's claim is they start it at that viscosity rather than it shearing into that range. The HT/HS of most oils in the 30 weight conventional range are around 3.0, so I would estimate it to be 2.9 or 3.0 for that oil. The information is not published. The Castrol GTX is a pretty thick formula (as are all of their oils) and it is 9.1 cSt at 100 degrees, most oils in the 5W-20 grade are 8.0 (for Havoline) to 8.6 cSt, typically around 8.4 with a HT/HS of 2.6. If the HT/HS increases proportionally to the viscosity, I would say it is around 2.7. The funny thing is, I think the difference in wear would as much come from the poor cold flow performance of the GTX relative to the 5W-30 Havoline. I know Gary Allan has done different viscosity experiments, I am just curious what the range of opinion on this is from the AEHaas types to people running straight 30 weight.
 
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I've been very tempted to do this myself. I assume from your last comment you've seen Aehaas writings on the subject and it sounds like your use would be perfectly appropriate for it. Why not go directly to the Havoline 5W-20 and try it out? That way the results would be less ambiguous than going to an oil that (I'm inferring from your post) is heavier cold despite being lighter hot. I don't think you'd even see a difference in wear. Might be noisier mechanically though, if that bothers you (it does bother me).
 

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I would like to try incremental steps before doing something drastic. Going from an 11.3 cSt, 3.3 HT/HS oil to a 8.0 cSt, 2.6 HT/HS oil is a pretty significant change. The cold flow characteristics of GTX are nothing spectacular but I would think that it would offer more of a buffer in the event of a high temperature scenario. Safe better than sorry. In the winter I would be more inclined to run a thinner oil yet. Castrol doesn't post enough, or complete enough specifications of their oil to get a really good grasp on what it is like through the temperature range. They basically post it as meeting the minimums for cold weather performance for the grade, its viscosity at 100 degrees, and specific gravity. For example, the 5W-30 grade is the only one which passes GM 6094M so its cold pumpability is listed at 40,000 cP at -35 rather than 60,000 for the others. I am just trying to find a readily available dinosaur juice that may offer a "5W-25" type performance rather than 5W-30 or 5W-20.
 
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I wouldn't give it another thought...you've thought it through thoroughly at this point. I've run 5-20 in Subarus spec'd for 5-30, the UOA's were stellar, as always. NO noticeable consumption with the 5-20. What you describe sounds perfect for making that change.
 
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The wife has recently taken my Cobalt away from me. Her driving is mostly city/suburb. Speeds seldom get over 50. What little highway she drives is once a month about 200 miles round trip. The car will be needing an OC very soon. I plan on using Amsoil XL 5W-20, has 5W-30 XL in now. Will run a UOA for giggles around 1K miles into the cycle to see how it goes. FWIW I did the same on her old car an 02 Olds Alero V6. That car had almost 180K miles before I shipped it out west to the daughter. Still runs great, mileage stays right where it always has etc etc uses very little oil. Other than an intake manifold gasket issue, which the Olds is known for there have been no problems.
 
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MGregoir

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Well, most of us know that 10W-30 in place of 5W-20 won't hurt anything, it just won't flow as well when it is cold, and it will stay thicker when it is hot. 15W-40 in place of 5W-20 wouldn't do any favors in the long term, especially in cold climates, but 10W-30 over 5W-20 won't hurt anything, it just won't help. 5W-20 over 5W-30 might offer me some advantages. If I see no increase in wear, and improved fuel economy and cold weather/cold start performance, I will take it. Most people just don't drive vehicles or in conditions that require thicker oils. This summer in the car in question I ran 10W-30 in place of 5W-30 and noticed it was quieter on starts, but at the same time even a conventional 5W-30 once it got to be winter seemed to be on the thick side. You live in the right climate to be running 10W-30 pretty much year round, I would be disadvantaged by it six months of the year. In California, I would be running Amsoil ACD in pretty much anything with a motor and laughing. I am considering running a heavier 5W-20 in summer and a 0W-30 synthetic in winter, because that's what my conditions require. People in Australia must think we are nuts talking about 10W-30 being thick when they use 20W-50 in most everything there.
 
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 Originally Posted By: MGregoir
Well, most of us know that 10W-30 in place of 5W-20 won't hurt anything, it just won't flow as well when it is cold, and it will stay thicker when it is hot.
I'm thinking Valvoline Synpower 10W-30 will outflow a dino 5W-20 when cold and offer better protection when hot.
 

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 Originally Posted By: Merkava_4
How about a "10W-30 in place of 5W-20" thread for a change? \:\(
YEAH! I second that motion! THICKER IS BETTER!!! \:\!
 
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I was thinking the exact same thing. It should be named Castrol GTX 5W28 ;\) I mixed a single qt of another thinner 5W20 for my winter driving (5W30 spec). For still cold spring I'll likely mix even more of GTX 5W28. Like you said it is almost a 30, so no difference really. In fact, I was rather annoyed to discover that it is a 28 after I bought a case. Is it that hard to add another significant digit to labels???? I have GTX 20 being more like 28 and Esso XD3 0W30 being more like 38. Geez. So yes, thick 20s like that should be fine. For summer I'll switch to a 10W30, at least for my older engine.
 

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Looking at the specs for them, I don't know if I could commit to saying Valvoline SynPower 10W-30 is better than All-Climate 5W-20 in the cold. Cold crank is 4700 cP for the dino 5W-20 at -30, the SynPower 10W-30 is 4700 cP at -25. Equals the performance at a lower temperature. The cold pumpability for the dino is 16,000 cP at -35, and for the SynPower it is 13,700 at -30. The synthetic has a small pour point advantage over the dino, -36 for the dino rather than -39 for the synthetic. I would say that once you factor in price, cold weather performance wise, the 10W-30 synthetic doesn't get near the dino 5W-20 from the same producer with a ten foot clown pole.
 
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 Originally Posted By: Merkava_4
 Originally Posted By: MGregoir
Well, most of us know that 10W-30 in place of 5W-20 won't hurt anything, it just won't flow as well when it is cold, and it will stay thicker when it is hot.
I'm thinking Valvoline Synpower 10W-30 will outflow a dino 5W-20 when cold and offer better protection when hot.
X2..
 
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 Originally Posted By: MGregoir
Looking at the specs for them, I don't know if I could commit to saying Valvoline SynPower 10W-30 is better than All-Climate 5W-20 in the cold. Cold crank is 4700 cP for the dino 5W-20 at -30, the SynPower 10W-30 is 4700 cP at -25. Equals the performance at a lower temperature. The cold pumpability for the dino is 16,000 cP at -35, and for the SynPower it is 13,700 at -30. The synthetic has a small pour point advantage over the dino, -36 for the dino rather than -39 for the synthetic. I would say that once you factor in price, cold weather performance wise, the 10W-30 synthetic doesn't get near the dino 5W-20 from the same producer with a ten foot clown pole.
also take into account if your motor overheats... what would you rather have in your motor?? a synthetic that can take hard abuse or a 5w20 dino that will coke up in that extreme heat? correct me if i am wrong i am merely speculating :-)
 

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Well, I have never had the temperature gauge on my car above 5/8 in even the worst conditions so it isn't an issue for me. If I blow a rad hose, I'm parking it on the side of the road and calling a tow truck. If I was going to run a synthetic, why not run the 5W-30 synthetic that gets both ends? When there is so much good 5W-30 out there now, I can't imagine running 10W-30 just for the sake of running 10W-30 synthetic instead of 5W-30, especially when 5W-30 is specified. If I'm going synthetic full time, it's straight to 0W-30 oils that nail both ends of the spectrum. What I am chasing here is that my car doesn't see severe use, and is in a cold climate, so I am looking for a fuel savings when the engine isn't at operating temperature and better oil flow most of the time. It's not loaded severely enough to wake up in the middle of the night screaming worrying about the oil not being thick enough, I don't see oil temperatures to make a heavy 30 weight worth it when a light 30/thick 20 would do. As well, this engine was designed in an era when SG oils were around and 5W-30 would shear down to a 5W-20 anyways, and the engines lived regardless. When I can get the dino to do this for $2.57 a quart regular priced, when SynPower/Platinum in any grade are at least $6 here, and get a lot of the performance benefits I seek in a synthetic, I see it as a cost effective and reasonable way to improve engine operation. Better oil flow, easier cold starting, better fuel mileage...no change in price. If the 10W-30 was better for the job, I'd be the first in line to use it, but in this case thinner offers more real world benefits than thicker. The main reason 10W-30 is still biggest on the market in a world full of shear stable 5W-30s is because people still think that anything less than it is [censored] water regardless of if it is going to offer them better performance or not. The one thing that 10W-30 beat 5W-30 on was shear stability and that becomes less of an advantage every generation of oil, and the 5W-30 basically has it beat in every other aspect. I have used 10W-30 in this car and the advantage it showed me was it was quieter. That's it, and once it got below 50 degrees the car was ready to reject it. Same reason 10W-40 is the second most popular consumer grade. It's not the right oil, people just have it in their head that it is.
 
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When I think of 'mixes' to run in my car, I think a really good one for a Canadian winter would be: 2 litres of PC Artic 0W-30 (10.3 cst) and 2 liters Pennzoil Platinum 0W-20 (8.36 cst), which comes out at almost exactly 9.3 cst, so it would have really good low-temp properties (both great 0W numbers); and be on the border between a 20 and 30-weight at operating temps for good fuel economy.....wuld love to try that!
 
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Toyota has approved the use of 5W-20 Group IV in engines previously speced for 5W-30. These include the 3.0L V6 1MZ-FE Camry engine and the 3.4L 5VZ-FE truck engine, as well as others.
 
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From the UOAs I have looked at, it looks like after 3000 miles that Castrol GTX 5W-20 and Pennzoil 5W-30 are basically equal oils. Both run down to 8.5 to 8.6 cSt after 3000 to 4000 miles it seems like. 8.5 cSt is the lower limit of what I would be comfortable with running for post-shear viscosity, and I think that is about the limit of what the engine would like. It's almost tempting to try a 8.5 cSt synthetic that will hold its grade to see if it stays in that pocket, maybe even a 0W-20. 8.0 cSt with room to shear is just too thin for me. Right now I am using Mobil 1 5W-30, and at 5000 km I will pull it and send away for a UOA to see what kind of wear numbers it has before trying anything. I think Amsoil XL 5W-20 might be the next trial on the list, but I don't generally extend drains so that will be for naught other than the performance increase. The Havoline DS UOAs I have seen shows it shearing down to the 9.1 to 9.5 cSt range for 5W-30. It's all about this nice triangular pocket of the cost of the oil, the benefit of fuel and possibly wear savings, and if possible the increased wear/risk of damage to the engine. An inexpensive synthetic 5W-20 that holds its grade, or a thich 5W-20 that shears down but stays in range looks to be the pocket for this. I just wish Castrol would publish better specs for GTX than the limits of the grade, because I am sure the oils are probably better than that...at least marginally.
 
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Keep in mind that in the 1970's the first Mobil 1 5W-20 was only 7.5 cst at 100C, and Mobil claimed that b/c of the basestocks used, that even that thin of a 5W-20 had better film strength than a 10W-40. Lots of people ran this oil in the big V-8's of the day, and didn't have any problems. So surely a modern 20-weight in the 8-9 cst range would survive in todays engines, unless they are already seriously worn.........
 

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Well, it's finding an oil that stays in that 8 to 9 cSt range solidly, if I am going to do it, I want to do it with a "known quantity."
 
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