Use straight weight in warm weather

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8,467
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Colorado
It used to be acceptable years ago to use straight 30 wt. oil in Saturn cars. But now it says in the owner's manual that straight weight oils are not to be used. You would always have somebody putting 30 wt. in the engine in the wintertime. I know a guy who was a race car driver and he used to use 30 wt. in the summertime and 20 wt. in the wintertime. But today he uses multi-viscosity. Redline has some straight weight oils that I think are like multi-viscosity oils in their effectiveness.
 
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Dixie
JT, If you want to compare a straight 30wt synthetic diesel oil to the PC, Duron 0w-30, let me know. I'd be interested in seeing how this comes out? I'd be willing to split the cost with you, in the interest of science. I've run the "ACD" formulation in a small fleet of six cylinder, Mercedes diesel trucks back in 1980-1981,but I've never done an oil analysis ... Maybe we'll have to wait until next summer? Isn't the snow already flying up there? [Wink] TS
 
From what the article said (who knows where it came from or what the graph looks like), The oils were tested at low temperature (simulating cold starts ?) midrange temps, and high temps (simulating overheat conditions ?). While interesting, there is not enough factual data for me do draw a conclusion. It is interesting that 30W APPEARS to excel at cold temperatures, compared to 10w30 & 10W.
 
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Houston, Tex
One thing to notice is that this test only addressed one wear point of an engine, the cylinders. Whatever the conclusions of this test, they do not necessarily apply to the bearings, cam and lifters, valve guides, etc.
 

Jim

Thread starter
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Grand Rapids, Michigan
It’s not snowing yet but it might as well be. I bought a new air cooled motorcycle (Moto Guzzi) and I am looking for the perfect oil for it. It will never see cold starts so that is why I am interested in straight weight oils. The manual calls for a 20W50 and I have been using Schaeffer’s 15W40 in it. I have only put 3000 miles on it and have changed the oil 3 times. The oil always comes out quite dark. Maybe after break-in it won’t be so hard on oil. I would like to try a straight 40W synthetic but can't find any.
 
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98245
quote:
Originally posted by Jim: I bought a new air cooled motorcycle (Moto Guzzi) and I am looking for the perfect oil for it.
A lot of us use Mobil 1 SS 15w50 "red cap". It has been putting out very good UOA results with my modified '99 Honda Magna. It holds its viscosity well, has a solid additive package (high ZDDP levels & high TBN), is compatible with wet clutches, and is cheaper than most MC-specific oils.
 
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BC, Canada
2manywheels; One part at a time. Valve guides: boundry lubrication conditions most of the time, reducing wear depends mostly on the additive package. Camshaft and lifters: Very high mechanical loading and risk of skuffing. Not a happy place for VI improvers. Plain main and rod bearings: dependant on a full film of oil for lubrication ( hydrodynamic) to keep these parts seperated. Cylinder walls pistons and rings: A bit of everything as lubrication is dependant on hydrodynamic conditions, and boundry lubrication AW additives that may include FMs. Dirt and other debris is likely the cause of most engine wear reguardless of which type or grade of engine oil is selected. That is why for spring summer and early fall, I like to select a moderatly priced mono-grade engine oil that seals out combustion by-products. It might have been wishfull thinking but the SAE 40 I used last summer on a long trip appeared to stay cleaner looking longer than other engine oils I've tried. Mono grades can be a pain in the butt as multi grades can be so convienient. XXW40 for summer and XXW30 in winter. Multi grade minerals with VI improvers in air cooled engines??? Not in my lawn mower.
 
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Pittsburgh, PA
[Cool] Yeah, but I bet that was on a dyno in a very controlled environment. Some car from the 60's would be okay on straight 30 weight but modern cars have a lot tighter clearances and run hotter, so I think you need a good multi-grade now.
 
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Columbus Ohio
In a constant rpm test such as the aforementioned, a straight 30 would not be at a disadvantage, and the viscosity would remain roughly the same between a 10w30 and a sae30. At cold temps the 10w30 would have an advantage.
 
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5,915
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Waterloo, ON
quote:
Originally posted by JohnnyO: [Cool] Yeah, but I bet that was on a dyno in a very controlled environment. Some car from the 60's would be okay on straight 30 weight but modern cars have a lot tighter clearances and run hotter, so I think you need a good multi-grade now.
Johnny O, keep in mind that a 10W30 and a straight 30 weight oil are the same viscosity at operting temps
 
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4,844
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Saskatchewan
quote:
Some car from the 60's would be okay on straight 30 weight but modern cars have a lot tighter clearances and run hotter[/qb]
Also keep in mind that the 30 weight is better at high temps than a multi-grade. Multi-grades are used for startups. Once the oil is at operating temperature, the multi-grade component is no longer useful. [ October 29, 2003, 08:59 PM: Message edited by: rpn453 ]
 

Jim

Thread starter
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268
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Grand Rapids, Michigan
Mercedes-Benz Engineers (Rudolf Thom and Karl Kollman)along with pair of Shell Oil engineers (Wolfgang Warnecke and Mike Frend)wrote an SAE technical paper (No. 951035) on "Extended Oil Drain Intervals: Conservation of Resources, or Reduction of Engine Life?" Among the many interesting results presented in the paper was a graph showing cylinder-wall wear-rate Measurements correlated with cylinder wall temperature. Cylinder wear rates(in micrograms per hour) were monitored as a function of cylinder-wall temperature in a test engine specifically fitted with radionuclide-impregnated cylinder liners. Three test were done so that three different kinds of oils could be used. In one test sequence, a straight 30 weight oil was used; in another, 10W-30 multigrade; and in the third, straight 10 weight oil. (The test engine was a Mercedes-Benz OM 616 2.4-liter, 4cylinder diesel.) In each case, the engine was operated at fixed speed, torque and temperature conditions until constant wear rates were observed. Wear rates were then plotted against cylinder wall temperature. The graph of cylinder-wall wear rate versus cylinder wall temperature tends to be bathtub-shaped, with wear increasing sharply at each temperature extreme (as you'd expect). But while two of the oils turned in very similar wear performance, one oil stood out as protecting the engine against wear at the extremes of temperature. That oil was plain SAE 30 (Straight-grade 30-weight). At either extreme of temperature, the maximum wear rate with 10W-30 was more than double that of the straight SAE30 oil. (The worst performance was turned in by straight 10-weight.)
 
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716
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98245
quote:
Originally posted by Jim: The graph of cylinder-wall wear rate versus cylinder wall temperature tends to be bathtub-shaped, with wear increasing sharply at each temperature extreme (as you'd expect). But while two of the oils turned in very similar wear performance, one oil stood out as protecting the engine against wear at the extremes of temperature. That oil was plain SAE 30 (Straight-grade 30-weight). At either extreme of temperature, the maximum wear rate with 10W-30 was more than double that of the straight SAE30 oil. (The worst performance was turned in by straight 10-weight.)
I wonder if they simulated cold starts? Or did they keep the engine running the entire time? If it's true that most engine wear occurs on cold starts, then the 10w30 should provide less wear than a straight 30.
 
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94
Location
Seattle
quote:
Originally posted by JohnnyO: [Cool] Yeah, but I bet that was on a dyno in a very controlled environment. Some car from the 60's would be okay on straight 30 weight but modern cars have a lot tighter clearances and run hotter, so I think you need a good multi-grade now.
I've lost count of how many people have said this, but I think your dead wrong. True they are able to hold tighter tolorences these days, but that doesn't mean they are using tighter oil clearances. I dug thru some Chiltons manuals to compare the recomended rod and main oil clearances for a 1969 Chev 350 (truck) and a 1994 Chev 350 TBI (truck), the figures below. If anybody can prove or disprove any of this, please do. 1969 350 .0008-.0024 main .0007-.0028 rod 1994 350 TBI #1 .0008-.002 main #2/3 .0011-.0023 main #4 .0017-.0032 main .0013-.0035 rod
 
quote:
Originally posted by Kompressor: I dug thru some Chiltons manuals to compare the recomended rod and main oil clearances for a 1969 Chev 350 (truck) and a 1994 Chev 350 TBI (truck), the figures below. If anybody can prove or disprove any of this, please do. 1969 350 .0008-.0024 main .0007-.0028 rod 1994 350 TBI #1 .0008-.002 main #2/3 .0011-.0023 main #4 .0017-.0032 main .0013-.0035 rod
It looks like for the rod bearings the clearance used to be tighter back in 69 and also the same or tighter for the mains. Urban legend about tight clearances? Maybe tighter for an engine designed in the last few years and not based off of an older engine? [ October 30, 2003, 01:48 PM: Message edited by: V6 Diesel ]
 

Patman

Staff member
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Oakville, Ontario
I've got a question I've been wondering about for a while on this subject. If there is a synthetic oil which is labelled as a 10w30, but does not use any viscosity index improvers whatsoever in it, would it qualify as being technically a straight 30wt? In other words, could you not build a straight 30wt oil in such a way that it would qualify for 10w status too? And at the same time, if it really were made with some incredibly good base oil, could you ever get a straight 30wt which would technically qualify as a 5w30?
 
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4,844
Location
Saskatchewan
quote:
Originally posted by Patman: If there is a synthetic oil which is labelled as a 10w30, but does not use any viscosity index improvers whatsoever in it, would it qualify as being technically a straight 30wt?
I think you could label any 10W30, 5W30, or 0W30 as SAE 30 (someone correct me if I'm wrong please). You'd lose a lot of the market on that version of the label, since less people buy straight weight oils. As well, it probably wouldn't be able to meet many of the specifications commonly associated with an SAE 30, so you'd lose much of that market too. With a good synthetic you can meet many of those specs and still sell it as an XW30, which increases your potential market. Check out Amsoil Series 3000 5W30 H.D. Diesel Oil, for example. Seems to meet all of the specs that any SAE 30 would meet, and you can sell it to us Canadians in the winter! [Canada] http://www.amsoil.com/products/hdd.html
 

KW

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1,686
Location
Central Arkansas
quote:
Originally posted by Patman: I've got a question I've been wondering about for a while on this subject. If there is a synthetic oil which is labelled as a 10w30, but does not use any viscosity index improvers whatsoever in it, would it qualify as being technically a straight 30wt? In other words, could you not build a straight 30wt oil in such a way that it would qualify for 10w status too? And at the same time, if it really were made with some incredibly good base oil, could you ever get a straight 30wt which would technically qualify as a 5w30?
I sort of thought that was the way synthetics were made. A straight weight oil that worked good in the cold with out all the VI.
 
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