Can all oil pumps handle heavier weight oils?

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33,974
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Southern NJ
It was mentioned in another thread how certain car manuals say NOT to use a 40wt oil or higher. Being we always focus on clearances and viscosities, can most modern engine oil pumps handle a thicker weight oil and could this be a reason why they say NOT to use it?
 
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11,006
Location
Canberra ACT Australia
No It I bet it will still be CAFE alone. Find me any engine you like and I'll put 25W70 in it and if it breaks I fix at my cost. Now I wouldn't use 25W70 in Alaska or other such uninhabitable places but anywhere temperate or hot it would be fine. I've run 25W70 at lower than -10C in the Snowy Mountains here in a Mazda 626 turbo that US mandated a 10W30 I believe. NA citizens spend way too much time worrying about viscosity IMO.
 

Al

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19,161
Location
Elizabethtown, Pa
Well even at 140 F a 10W-30 is 30 cSTs- thats a 70 wt. oil at 210F sportsfans. Cars seem to run at engine temps at less than 140 F all the time [Smile]
 
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9,448
Location
USA
Seeing how my entire family does the M1 15W50 in warm weather 10W30 in winter. We have done this on Fords,Chevy's, Mopars,Toyota's, Mistu's, Alfa's,Citroen etc....... I fill pretty safe that oil pump clearances are not that big of an issue with thickers weights at the right ambient temp. Now the reverse is not always true. The Dodge 4.7V8 had to have it's oil pump specialy clearanced for 5W30. The oil pump was the only part on the entire engine that had to be re-clearanced when they decided to recomend 5w30 as the primary oil weight.
 
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917
Location
Singapore
I've been using 50wts in my vehicles since the beginning of time. Over here in this hot & humid country, 50wts are very common, 40wts only started appearing 2 years ago, and 30wts are rare & hard to find. Even the Toyota dealership here is putting in mineral 20w50s in new Corollas! If you want synthetic, they put in Castrol syntron 5w50. Over at the carrefour shopping mart, Mobil 1 SS 5w50 is lining the shelves and selling like hotcakes.
 
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8,711
Location
Nothern USA
Oil pumps are positive displacement pumps. Unless the oil is too thin for its clearances, the pump is going to deliver a certain volume for every revolution, at least until the drive snaps. Hope you have adequate bypass with cold, thick oil, because otherwise, something is going to break.
 
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450
Location
Louisville, KY
quote:
Originally posted by Al: Well even at 140 F a 10W-30 is 30 cSTs- thats a 70 wt. oil at 210F sportsfans. Cars seem to run at engine temps at less than 140 F all the time [Smile]
Excellent Point. Fred... [Smile]
 
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3,593
Location
Outside smalltown, IL
Oil pumps are positive displacement gear pumps. They could care less about thick fluids. I've worked on equipment where we used gear pumps with fluids of 650,000 cp. IOW, over twice as thick as peanut butter. Too thin will give you more problems. The pump clearances need to be very small or the pump efficency drops off from leakage around and between the gears..... [ November 25, 2003, 12:14 AM: Message edited by: jsharp ]
 
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917
Location
Singapore
I recently installed a very accurate oil pressure gauge in my 4cyl camry. http://web.singnet.com.sg/~kppjw/Oil_Gauges7.jpg Presently using BP Visco 7000 0w40. There is not a lot of difference between hot & cold max oil pressures. Ambient temp 30C. Max oil pressure (cold) [email protected] of 120.0 cSt = 5 barg Max oil pressure (hot) [email protected] of 14.5 cSt = 4.5 barg The oil is eight times thicker at startup, yet the oil pressure is only 0.5 barg difference. I've previously used Shell Helix Ultra 15w50 and Castrol RS 10w50 with no problems whatsover, and got some decent looking UOAs if I might add. The oil filter I use doesnt even have a bypass.
 
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11,006
Location
Canberra ACT Australia
Ken4 I wish we could get Visco 7000 0W40 here but BP won't have a bar off it. I'm stuck with the 20-litre drum of Visco 5000 5W40 purchased recently which Timkens very well and was cheap but it is a pretty thin 40W at 13.95 cSt @ 100C. Should be excellent for my Outback.
 
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43,651
Location
'Stralia
Only problem that I've seen with too high a pressure (regardless of oil viscoscity) is failure of the roll pin when people try to drive the pressure up too far.
 

Patman

Staff member
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21,989
Location
Oakville, Ontario
quote:
Originally posted by Al: Well even at 140 F a 10W-30 is 30 cSTs- thats a 70 wt. oil at 210F sportsfans. Cars seem to run at engine temps at less than 140 F all the time [Smile]
True, but then a 20w50 oil at 140F will be even thicker still. That's the point, a very thick oil like that, combined with cold temps, could be too much for the oil pump which has been designed to run on a 5w30/10w30.
 
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5,785
Location
Dixie
Buster, The standard CCS test temps are supposed to represent a conservative low temp limit for use of a particular SAE grade. For years the German engine manufacturers have used them in precisely this manner. So you'd see them recommending -10C/-15C/-20C/-25C, etc as explicit low temp limits .... For example, until 1999, VW/Audi/BMW/Mercedes used to recommend the 10w-40/10w-50 grades down to -20C/-4F, the SAE,15w-40/15w-50 grades down to -15C/+5F and the 20w-50 grade down to -10C/+14F. They allowed the use of 5w-50 oils for all temp ranges ....With modern fuel injection systems, engines start at lower temps and with thicker oils than every before. Most of the German auto makers now recommend low viscosity synthetics, ie 0w-30 through 5w-40 for all temps. However, some of this is so you can use the same oil year round, even if you live in Alaska, and some is based on fuel efficiency concerns. Common sense indicates that you'd like the oil to be as thin as possible to enable easy cold temp starting and to optimize fuel efficiency during the warmup phase. However, most lube engineers will tell you that if the oil is thin enough to allow the engine to crank easily, it's safe to use under those conditions, regardless of the SAE grade. The borderline pumping temp (BPT) is defined by the SAE at the point where the viscosity of the fluid thickens to 60,000 Centipoise - that's about ten times the CCS limit for any SAE grade. If the fluid is thicker than this you'll get cavitation and extremely high engine wear due to lack of oil flow .... Tooslick Dixie Synthetics [ November 25, 2003, 07:32 AM: Message edited by: TooSlick ]
 
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5,785
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Dixie
Buster, I've always rejected the notion that engineers all have poor communication skills. [Wink] BTW, I'm seriously thinking of retiring at 50 and becoming a HS Physics teacher. I figure if I can teach a finance major from NJ to become a shade tree tribologist, anything is possible ...LOL! Ted
 
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8,711
Location
Nothern USA
quote:
Originally posted by Ken4: .... snip The oil is eight times thicker at startup, yet the oil pressure is only 0.5 barg difference. .... snip . The oil filter I use doesnt even have a bypass.
Engines have 2 bypasses. One is directly off the oil pump, bleeding oil back to the crankcase. It is spring loaded to limit the oil pressure delivered to the engine to a maximum low enough to avoid breaking things. The oil pressure may reach the maximum under a range of conditions, but would never exceed it except in extreme condition where the oil flow out the bypass wasn't enough to limit the pressure. The other protects the oil filter from more differential pressure than it can take. A burst oil filter would be a big mess. Usually they are built into the filter itself, but GM and others build it into the engine.
 
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11,006
Location
Canberra ACT Australia
T you got it in one. I shudder every morning I start the Outback that has 5W30 in it and the engine rattles. Never did that with Delvac 1 5W40. Still it will be outa there anyday after finishing final RX clean (3,500kms) and I'll get something thicker in there and get rid of the racket hopefully.
 
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2,480
Tooslick, my 1994 BMW owner's manual actually approves a 15W down to -20C and then goes on to say that these are based on average exterior ambient temperatures and that the temperature may be above or below this for short periods without problems. In other words, we're all too freaked out (and I was among those) by higher viscosity oils not recommended by disposable U.S. vehicle owner's manuals. If anything, what I've found is colder temps. allow for thicker viscosities to work even better at coating the engine parts rather than flowing into the pan requiring pumping. ie. the cling factor is higher and the oil is already where you need it...on the parts. But, then this is contrary to the 0W crowd...however, the same is true for a 0W...only, it happens at -35C.
 
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