Shouldn't the manual just specify weight & let the customer figure the "W" rating?

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Aug 12, 2003
I've read so many manuals that have that stupid chart with overlapping oil grades and ambient temp BS. After the chart, there is the obligatory mention of (usually) 5w-30 or 10w-30. [I dont know] This method of decision-making is somwhat contradictory and definately confusing. [Frown] Would'nt it be better for the mfgs to explain the "W" winter cold-cranking rating better and JUST say: "hey, the car takes SAE 30 weight with whatever cold-cranking rating you think you need"? I can see requiring a 40 weight when ambient temps get desert-like, but that aweful chart is no good. This confusing system probally turns many people from trying to learn about their oil specs, mfgs should do better explaing. (more people ould use 15w-40 if they knew it cranked to -10 degrees)
I understand your point, but I kinda liked those historical charts with 7 or 8 oil choices. Now, my '90s vehicles have about two choices: 5w30 and 10w30. I understand the new Fords have one choice: 5w20.
The Duramax diesel supplement states 15W40 preferred, but use 5W40 below 0 F. They also state you can use 10W30 between 0 and 100 F. They say not to use any other grades period. So what would be wrong with using Amsoil's 5W30 S3000 diesel oil, below 0 and 100F? [I dont know] I know some Duramax owners are.
The old ambient temp viscosity charts were far better then todays recomendations. The temps charts were usualy set up for conventional oil but some companys also provided charts for synthetic. THe old charts asuume that the owner is smart enough to select the best oil for his enviroment given a little guidence. THe old style charts were primarily concerned with engine performance and protection . Todays method is primarly concerned with fuel ecconomy in N. America. THe old style of charts is easy to use but requires some independent thought. You look at what the high and low temps are going to be dureing the course of the OEM recomended OCI and select an oil weight between those temp ranges. You then factory in you prioritys like wear reduction and fuel ecconomy. I prefer to have choices as the owner of a vechile rather then be told what I can use! Their is no single weight of oil that will protect in all engines and in all ambient temps 100% of the time. THe idea of a universal oil is not a reality. It is true though that their are no oils available that could work well in 90% of peoples non-comerial cars and trucks year round with little performance to be sacrificed( In USA and Canada).Delvac1 5W40 with a little bit of tweaking, Redline 5W40, Amsoil S3000 5W30 come to mind. With the above said I would still like to reserve the right to run 20W50 or 15W50 if I like etc.... P.S. I almost forgott. They might also be trying to controll the amount of VII's buy controling the range allowed. THis would prevent owners from useing a fluid full of VII's. [ December 11, 2003, 07:07 PM: Message edited by: JohnBrowning ]
I'll tell you why the "W" number is stipulated: The EPA demands it and in fact manufacturers are to persuade consumers to use 5w30 or other energy conserving oils. Not only that the EPA has regulations that explain how the manufacturers are responsible to make energy conserving oil readily available. Crazy eh?
The answer is because you can't. my manual it states that a 0w-30 for example is not as robust as a 10w-30 by about 10F or something (on the scale). Likewise, a 5w-40 for example, has a lower high temperature number than a 15w-40.... Guess my chart (1994 BMW) recongnizes that the higher ranged viscosity oils will ultimately thin out and illustrates that with a lower acceptable upper temperature recommendation. So, you cannot make a blanket 30 weight recommendation just like the "W" number.
The EPA demands it and in fact manufacturers are to persuade consumers to use 5w30 or other energy conserving oils
Yeah, in fact, isn't the mpg test done on a cold engine, just start it and drive off using the recommended factory oil? I remember this issue coming up before. A light 5w-30 would be indicated then, in my case a 0w-30.
My '96 Audi manual has that overlapping chart. The chart is not confusing at all, at least not to me. I mean, what exactly can be misunderstood? [Confused]
German manufacturers have the only engineering based, oil viscosity/temp charts ....They used to allow anything from a 5w-30 to a 10w-60 to be used in the same engine, depending on the lowest ambient temp you are likely to see. The charts from as recently as 1999 for BMW and Mercedes restricted high temp use to 15w-40/5w-50/15w-50/20w-50/10w-60 grades, and relegated 5w-30/10w-30 and 5w-40/10w-40 grades to temps < 78F/25C in most cases. With the advent of better, low viscosity lubes, the charts for German vehicles have become simplified, or dumbed down if you prefer like "Dr T". They now list 0w-30/0w-40/5w-30/5w-40 for all temp use in 95% of their engines. There are still some exotic motors like the BMW M3's that require thicker lubes, so you still have to know what you are doing with those .... Tooslick Dixie Synthetics
Additionally, not all 30 weights are created A3. However, even with these I still think the old tried and true chart is a better indicator than to use the artificial thinking of all A3's are created equal. As you mentioned, if that were true, then the A3 BMW synth. 5-30 would suffice in ALL their engines...obviously it did not work for the M3/M5/Z8. I know...engine tolerances....
I like the charts, but they are very general. As noted above "not all 30 weights are created equally." I would like to see each manufacturer and each grade specify a temperature range for their oil right on the back of the can. Next time you are in a good parts store (that carrys a diverse variety of oils), look at the Motorcraft HD 15w40 oil. I just did the other day and it says not to use it below 20F. Ok, so that is right off the general table, but a synthetic 15w40 should say something more like for use down to, say, zero F or whatever it is. Two Group II dino 10w30s might get different temp ratings depending on base oil viscosity, VI improvers added, pour point depressants, etc. Then I could go into the store and look at Valvoline Allclimate, Maxlife, Durablend, and Syntech 10w40s and suppose they give minimum temps of, say, 5 F, 0 F, -5 F, and -10 F respectively. Then in winter I might go with the Durablend (since I don't use 100% synthetic), whereas otherwise maybe I would use AllClimate (actually I use Maxlife). Also, I might be inclined to use a good Group II+ 15w40 if it said good to 0 F. [ December 12, 2003, 01:32 PM: Message edited by: TallPaul ]
Originally posted by Pick: So what would be wrong with using Amsoil's 5W30 S3000 diesel oil, below 0 and 100F? [I dont know] I know some Duramax owners are.
Nothing. The reason its not recommended in 5w-30 even tho that brackets their recommendations is, that they cant count on you using a syn oil. Manufacturer probably like tha tight spread in a 10w-30 and 15w-40 for low VIIS. This is a sign that that engine likes a low VII +stable oil. Fred.. [Smile]
PS: I love those little charts. .. [Happy] Give you a real good sense of where the center mass of perfoamnce is for a given engine/temp combination. Fred.. [Smile] [ December 13, 2003, 01:02 AM: Message edited by: palmerwmd ]
I think that one reason the 5w30 recommendation is seen so often in American autos is because the manufacturer knows that many people don't know or care about oil weights and that 5w30 is a 'shotgun' oil. It will work ok in hot weather and very well in cold weather. Fuel mileage and emmissions is another reason. Getting oil moving quickly results in less engine wear and possibly less warranty claims. Just an opinion. [I dont know]
Shure, WE like the charts becuse it is our only insight into the mfgs specs and because WE are smart enough to decipher, eliminate and ignore the useless parts. The charts are a relic from a time when wide vis oils were a rarity and less functional then now. Maybe this system will be simplified for Joe Schmoe in the future. SAE 30 will be King and oil co.'s will always deliver cheap additive packs for cheap base oil delivering 5w cranking for _ _ _ _ _. (cheap)
Last I checked data interpolation was not a relic. Picking the lubricant with the best charteristics for the job(includeing ambient temps.) is the smarter way to maximize protection and performance. The charts require owner involvement. I find it difficault to belive that anyone that can read a thermomater(sp) and look at the chart can not make it work. How is choice bad? If someone is too stupid or lazy to use the chart they can alway add what ever weight the 710 cap says. No one forces anyone to use the charts. THe chart is their for those owners that choose to take an active role. It also shows the difference between cultures and customer bases. I can not even understand how some one could attack being given choices. How is it bad to be an informed consumer. If you flip it around you are saying that we should just be ignorant consumers that let the manufacture think for us. We should not question anything because the manufacture will always have our best interset in mind! I am also guessing that it might be hard to find 5W30 in Etheopia or 25W70 in Alaska or 5W20 in Germany etc.... From what I understand our neighbors in S.America can not even get good multi-weight oils unless they are imported from the N.America. I actualy think that car companys do their customers a disservice buy trying to dumb everything down to the lowest common denominator! P.S. Dr.T my 5W40 has a HT/HS of 4.6 or 4.7. So far at 17 degrees it still turns over easy as can be! No noise etc... [ December 13, 2003, 05:42 AM: Message edited by: JohnBrowning ]
My little chart for my 2002 Sportage has the fun 101 oil grade chart (ok, there may be ~ 7 oils)... Get this....... 5W-30 is not recommended over 32 deg F while 10W-30 is recommened up to ~85 deg F... (also 5W-20 only below 0 deg F!!!) Let's see you explain that?? Could it be engine characteristics?? It's a DOHC Mazda engine design......... The owners manual makes a big deal about selecting the correct grade for ambient temps.....
Originally posted by JohnBrowning: P.S. Dr.T my 5W40 has a HT/HS of 4.6 or 4.7. So far at 17 degrees it still turns over easy as can be! No noise etc...
Which 5w-40 are you using? Fred.. [Smile]
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