What is the truth about 5W-30 and 10W-30?

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8,467
Location
Colorado
Automakers have been recommending 5W30 oil in most new cars/trucks for several years now. And Ford and Honda have been recommending 5W-20. What is the truth about all of this? Is it really better to run 5W-30 throughout the year, including the summertime (or 5W-20 in the case of many vehicles), or is it better to run 10W-30 in the summer? I have never been convinced that 5W-30 and 5W-20 oils are the best for all year use. I think these weight of oils are selected mostly to meet CAFE requirments. In seems to me that 5W-30 and 5W-20 (and 0W-30) would be best foe the winter months. I once came across some information that many of the very engineers (speaking for the automakers) who were recommending 5W-30 oil throughout the year were actually using 10W-30 in their own cars/trucks in the summertime. And in Europe, people are often using thicker oils, sometimes in vehicles that have the exact same engine as vehicles sold in the US. You will hear about oils like 0W-40 and 5W-40 being used in Europe, but in my car's manual it says that the only viscosities that can be used are 0W-30, 5W-30, and 10W-30, with 5W-30 being preferred. It says that 10W-30 should be used only in warmer temperatures and if 5W-30 is not available. 0W-30 is acceptable in the wintertime.
 
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3,845
Quick answer to your question is this; CAFE drove the Auto makers to the thinner weights, oil blenders and adds guys didn't have it all in the bag initially and the lighter end of the chemistry cooked off and sludged engines. Oil co's build better oils and that issue abates some so they get comfortable with 5w-30. Then Ford and Conoco realize that with the newer designs they saw improved lube and engine performance and lead a charge for 20w oils, Honda likes flow rate for cooling and efficiency and joins Ford in leveraging the industry to 20w where we are now. Api bites into it and it gives close to a 3% improvement in efficiency CAFE wise so government is happy. Bottom line is this, a well built oil regardless of VIS ( to a degree) will work well in a moderately well maintained engine. For years we all ran oils that sheared to 20w or 10w at the rings and contact points under stress and heat while out of the high stress zones was a 30 or 40w or worse oil.... we just mistakenly believed they were 30w oils ! Detroit figured that out and now we are running vis stable 20w oils right out of the bottle, that shear very little. One other note, with the advent of very thermally stable adds and base oils the SAE vis readings of 0,5,10W and 20,30,40 etc. are outdated. We all would be much better served knowing the SUS or cSt vis at a given temp for that lube formulation. For my racing customers we don't even care if it is a 20 30 or whatever grade, we talk in cSts at a specified temp. I think the oil companies are using the SAE vis ratings more for marketing than informing you on what oil to use. Many oils can meet multiple specs, for instance the 0w-30s could be marketed as 5w-30 or 10w-30 if the company wants to. Thats my take ...... Terry [ November 13, 2003, 04:46 PM: Message edited by: Terry ]
 
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Shippensburg, PA
How much fuel economy gain do you REALLY see going from a 10W-30 to a 5W-30? It would seem to me that the difference would be minimal once the engine is up to operating temperature.
 
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3,845
novadude, YOU MAY NOT NOTICE ANY DIFFERENCE, BUT CAFE WOULD. A 1 % MPG gain in a 500 truck fleet is meaningful but you would never see it in your car. Depends on the formulation but all things being equal the 5w-30 may have slightly less frictional drag characteristics allowing very a very small measure of improved MPG or performance. Case in point is the RL 10w-30 vs. their 5w-30 street oils. You will notice a difference in those two forumulas. TD
 
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2,533
Location
Pittsburgh, PA
[Cool] I switched to 0w-30 M1 on the last change in search of better mpg, too soon to say if it helped. I have a 2002 Ford Ranger 4x4 4.0, everybody on the Ranger boards I go to complains about the mileage on the 4.0. 14.7 on my last tank when I filled up today, it's rated 15/19. [Roll Eyes]
 
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2,480
IMO, there's little difference between A1 5-30 and 10-30. There is a difference when you're talking about 5-40's, 5-50's, 10-50's, 15-50's, 10-60...etc. In general, U.S. vehicles once ridiculed for being "disposable" are just what other manufacturer's are now subscribing to. It's only when the run into trouble that a change is performed eg. Toyota, Dodge, BMW. It's also obvious that a compromise has been made that any A3 oils (down to a 5-30 grade) would suffice for engines requiring thicker viscosities due to their performance or output. This has failed as well...eg. BMW. We know that racing/tracking a car usually requires a thicker viscosity for protection. So why wouldn't one use such a viscosity all the time? You make the choice. Grade should be based on external ambient temperature and geographic/climatic location. Else you are at the hands of manuf....and their interest is in selling and repairing more cars...not seeing that yours lasts forever...
 
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2,480
Did 10-30 come out first and then we were all told to switch to 5-30 and only now is 5-20 the oil du jour?
 
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3,845
Dr T, I have said this before but ideally I would like a low friction lube that would be say a 0w-60 oil with a VI of 200+. BTW Europe is now pushing 0w-20 type oils as pollution and emissions is driving product changes as never before. Even in diesels. TD
 
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453
Location
Galveston, TX
quote:
Originally posted by Terry: .....Europe is now pushing 0w-20 type oils.... TD
Then I say Europe is crazy. The way they drive (sustained high speeds), their ride is not gonna last. [Eek!]
 
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Location
BC, Canada
I wouldn't be surprised to see long haul truckers switching from 15W40s, that are very near 15W50s, to 10w40s, say with a 100C cSt of 13.8ish,insteasd of the 15W40's 15.2. If the lower viscosity can improve milage 2%, the savings will easly cover any increased engine wear. Also I would bet that FM Diesel lubes and a catagory established for fuel conserving Diesel engine oils will soon be established. The current HDMO offerings are almost like multi-functional fluids, covering hydraulic, power shift and manual transmission applications, as well as engine oil service classifications. [ November 13, 2003, 08:03 PM: Message edited by: userfriendly ]
 
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There's all kinds of misinformation out there...but I will say that I've never abused any vehicle that I've owned. Yet, my current keep-forever BMW has suffered (I'm hoping irreversible) from using 9k mi. intervals on BMW 5-30 synth.. Same on the family Volvo as I was growing up. Lightweight oils work to safe fuel economy in the short run, but then later on you lose power gradually and emissions go up.
 

Patman

Staff member
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21,989
Location
Oakville, Ontario
quote:
Originally posted by Dr. T: There's all kinds of misinformation out there...but I will say that I've never abused any vehicle that I've owned. Yet, my current keep-forever BMW has suffered (I'm hoping irreversible) from using 9k mi. intervals on BMW 5-30 synth.. Same on the family Volvo as I was growing up. Lightweight oils work to safe fuel economy in the short run, but then later on you lose power gradually and emissions go up.
My next door neighbors 3.1L V6 Sunbird is almost at 400,000km now, using nothing but 5w30 oil since new. He still passes emissions and says the car still has just as much power as new.
 
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3,593
Location
Outside smalltown, IL
quote:
Originally posted by Flimflam:
quote:
Originally posted by Terry: .....Europe is now pushing 0w-20 type oils.... TD
Then I say Europe is crazy. The way they drive (sustained high speeds), their ride is not gonna last. [Eek!]

They do drive like maniacs, but they don't drive nearly as much on average as we do. We think nothing here about driving 15-50 miles each way to and from work. A 1000 mile trip will just barely get me to one coast, or 1/2 way to the other. In europe you can cross 5 countries in less miles...
 
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My understanding is that CAFE tests are done on the manual recommended oil...0w sometimes. I guess the car is started cold and driven off for the mpg test, that would explain the 0w oils. Those small gains is why we see more narrow tires on stock versions of cars that can take 1 to 1 1/2 size larger, mpg.
 
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Dixie
Userfriendly, Amsoil is seeing fuel savings of 3.0%-3.5% with their Series 3000, 5w-30, in long distance fleet service under steady state conditions, compared to a 15w-40. For around town type service, you can see improvements of up to 5% ....much less viscous drag during the warmup phase. I think the standard may go to either 5w-40 or 10w-30 for the bigger trucks. The latter is acheivable with group II oils, but the 5w-40's will require the group III or PAO stocks .... Tooslick
 
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Location
palmer mass
i wish my 92 sunbird 3.1 was like that the engine has 140000 miles run like crap burns oil and gas and the car is just so cheap i hate it also have a 96 grand am 3.1 92000 miles pos typical pontiac sucks
 
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43,651
Location
'Stralia
quote:
Originally posted by MolaKule: My take is that if the HTHS' specs of the lighter oils are 2.8 or better, then you're probably safe.
Molakule, I'm still stuck on the issue of HTHS. Is a 0W-20 with an HTHS of 2.8 equally as protective as a 10W-40 with the same HTHS ? Economy wise, why should they be different, if their HTHS is the same ?
 

Patman

Staff member
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Location
Oakville, Ontario
quote:
Originally posted by Shannow:
quote:
Originally posted by MolaKule: My take is that if the HTHS' specs of the lighter oils are 2.8 or better, then you're probably safe.
Molakule, I'm still stuck on the issue of HTHS. Is a 0W-20 with an HTHS of 2.8 equally as protective as a 10W-40 with the same HTHS ?

I've never seen a 10w40 with an HTHS that low though. 10w40s usually have an HTHS of at least 3.6.
 
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2,480
All things being equal, the higher the HT/HS the better. ie. brand A 5w-30 with a HT/HS of 3.5 will most likely be a better oil than brand B 5-30 with a HT/HS of 2.8. Brand A will have more cohones. I don't agree completely however, that a Brand A 5-30 with an HT/HS of 3.5 equals Brand B, a 10-40 with an HT/HS of 3.5 because Brand B achieve it's HT/HS with a higher molecular weight base oil compared to a 5-30 that probably achieves it's HT/HS due to addatives.
 
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