Dangers of 5W-40 in a car spec'd for 5W-20?

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79
Location
Canada
I've got the option to obtain some synthetic 5w-40 oil(VW 502 00/505 00 and Porsche approved) at a very low price. It would be used in a Mazda3 2.0 that is spec'd for 5w-20 and changed at 12,000km intervals (after the warranty period expires). Are there any downsides besides potential loss of fuel economy ? Anyone think there's any danger to the engine aside from possibly a couple MPG and a couple horsepower?
 
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11,151
Location
Florida, Cape Coral
Take a look at the viscosit of the 5w20 vs the 5w40. Probably higher viscosity with the cold starts so higher start up wear. If your Mazda 3 is like my CX7 then you have a VVT system which probably won't work as well.
 
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9,808
Location
New Jersey
i would use 5w20 it flows faster and gets into all the tight spaces such as the bearings there is no need for the thick stuff with todays oils. we are in the middle of a rebuild now in our shop of a 2003 nissan in which the owner believed thick was better and 10w40 oil and a thickening additive he used on his last 1977 chevy was the best he was very wrong and still after showing him all the damage he is leary of using 5w30 he thinks its too "water like" i told him if he dont use the 5w30 the warrantee is void.. I explained to him that todays oils are so advanced and some of the clearances are so tight that thin is the only way to go.. His nissan has under 50,000 miles on it..
 

ArcticCat

Thread starter
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79
Location
Canada
Well I don't think you can really compare an old school 10w-40 (which likely has a good dose of low quality group 1 base oil, and likely has a [censored] additive package as it's not blended to meet any modern OEM specs, as no one in North America currently specs a 10w-40) to a modern Euro VW 502/505, Porsche Approved, and MB 229.3 approved fully synthetic 5w-40 oil. Aside from both being thicker oils, one is old school low-tech garbage and the other is a modern high tech synthetic oil. lol As for the VVT problem, it's a 2004, so that's not an issue with this car fortunately. Am I wrong in thinking that a high tech Euro full synthetic 5w-40 can be used in just about any modern passenger car?
 
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4,432
Location
Massachusetts
 Originally Posted By: crazyoildude
i would use 5w20 it flows faster and gets into all the tight spaces such as the bearings there is no need for the thick stuff with todays oils.
So you're saying that 5W40 won't get in his bearings?
 Originally Posted By: crazyoildude
.. I explained to him that todays oils are so advanced and some of the clearances are so tight that thin is the only way to go..
The thinner oils that are used today have nothing to do with engine clearances. Engine clearances haven't changed. The crank clearances in my Willys F-134 engine are actually tighter than a new Honda.
 
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4,620
Location
The Garden State
In my pre BITOG days I ASSumed "thickerer is betterer". So in my 1996 Zetec Contour 5 sp manual I used 5W-50 Syntec and Quaker State synthetic oils instead of the recommended 5W-30, which I had used for first 15,000 miles. Nothing horrible happened. It started ok, heated garage in the winter, but I noticed it was slower in the "get up and go department" than the 5W-30 and my gas mileage was several mpg less. Went back to Mobil 1 5W-30 and now Schaeffer's 7000 Blend 5W-30. All is well, the old "get up and go" plus my mpg's went back up. I'll stick with quality 5W-30 synthetics and blends in this vehicle. Whimsey
 
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4,450
Location
Kuwait
15W-40 is the recommended viscosity for that engine in the Middle East. Although the majority use 20W-50, which is also listed in the manual. In most countries, the manual provides you with a temperature chart, and you choose your viscosity according to your temperature range.
 
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1,855
Location
Australia
 Originally Posted By: Falcon_LS
15W-40 is the recommended viscosity for that engine in the Middle East. Although the majority use 20W-50, which is also listed in the manual. In most countries, the manual provides you with a temperature chart, and you choose your viscosity according to your temperature range.
Yep, and xW-20's aren't available outside NA so guess what are in the cars form the factory and first service on, 10W-30 or heavier.
 
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9,808
Location
New Jersey
im saying it wont get there quite as fast or cool as good thin is in i see it day in and day out todays 5w20 and 5w30 oils are so much more advanced than 20 yrs ago.. i remember when 10w40 and 20w50 was the oil to have its not that way anymore..When we rebuild engines we usually fill the crankcase with what the engine is called for and we have less than three percent call backs on our engines for oil related problems.. Thats my opinion today 20+ yrs ago it was thicker is better Also in my shop we offer 2 free oil changes on every engine we rebuild to assure that the correct weight is used.
 
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2,995
Location
Cedarbrae, Ontario
 Originally Posted By: crazyoildude
im saying it wont get there quite as fast or cool as good thin is in i see it day in and day out todays 5w20 and 5w30 oils are so much more advanced than 20 yrs ago.. i remember when 10w40 and 20w50 was the oil to have its not that way anymore..When we rebuild engines we usually fill the crankcase with what the engine is called for and we have less than three percent call backs on our engines for oil related problems.. Thats my opinion today 20+ yrs ago it was thicker is better Also in my shop we offer 2 free oil changes on every engine we rebuild to assure that the correct weight is used.
As an engine builder, what is your opinion on using a good quality synthetic straight 30 weight oil these days?
 
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9,808
Location
New Jersey
Im pretty partial to the multigrades and have not had much experience with the single grade oils for quite some time (late 70s early 80s but have always used strait 30 in my garden equipment with good results In my opinion strait 30 should be ok to use in the summertime but will it have the cleaning ability of a multigrade i dont know what i do know even in the summer a multigrade will still flow faster on the average.. I think other people such as johnny would be the one to ask i am an engine builder and although i know somethings about oil and engine clearances he is the one that worked in the oil industry and maybe he can answer this question better..
 
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2,435
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Mizzou-land
xxch4osxx wrote: "what is your opinion on using a good quality synthetic straight 30 weight oil". I would bet that most any "straight 30 weight" would qualify as a multigrade. Does anyone sell a synthetic straight 30?
 
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15,056
Location
Canada
 Originally Posted By: GMorg
xxch4osxx wrote: "what is your opinion on using a good quality synthetic straight 30 weight oil". I would bet that most any "straight 30 weight" would qualify as a multigrade. Does anyone sell a synthetic straight 30?
Amsoil ACD Straight 30.
 
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2,435
Location
Mizzou-land
Amsoil ACD 10W30/SAE 30 qualifies as a multigrade. That is my point. It is difficult to find a synthetic SAE30 that does not meet the cold viscosity requirements of at least a 10W due to the high viscosity index. From the Amsoil storefront: "Unlike conventional SAE 30 motor oils, AMSOIL ACD has a naturally high viscosity index and does not contain paraffin (wax). It has a -36°F pour point and qualifies for SAE 10W, making it an “all season” multi-grade lubricant with a wide operating temperature range. AMSOIL ACD is formulated without viscosity index improvers (VI). "
 
 Originally Posted By: ArcticCat
As for the VVT problem, it's a 2004, so that's not an issue with this car fortunately. Am I wrong in thinking that a high tech Euro full synthetic 5w-40 can be used in just about any modern passenger car?
You can absolutely use the modern synthetic 5W40 in your car withou fear. I simply can't understand why people have to try to instill fear of running a thicker oil when in fact your engine probably runs with a 40 weight outside of North America from the factory as others have stated. I'm not suggesting that it's the optimal grade, but at the very least, you will be very well protected without issue.
 
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1,798
Location
Saint Paul (ex-San Diego)
I agree with most of the opinions expressed here -- many engines with a 5w20 factory recommendation would have a 5w30 or 10w30 factory fill in other countries. Nothing seriously wrong with running a 5w40 instead -- maybe not the best, but not dangerous. And probably better than a 5w20, which provides marginal protection at best.
 
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