What's the deal w/0W30 oil?

I searched & found only two mentions in the forums; on one (re: losing oil pressure on inclines) Eagle said something like " ...[if you're using] God forbid, 0W30"; on the other thread the selfsame Eagle recommends it as a lubricant to someone taking his engine apart.

The Amsoil dealer (& website) seem to believe it's the greatest thing going. Is it something I should consider for my upcoming change to synthetic at 94000 miles?

It is supposed to flow faster on initial startups and have the flow rate of water, saw a new car getting it, that stuff came out of the bottle FAST. Not recommended for yours, mine or anyone elses I know. You want to stay at 10W or above, I've run 5w30 in the winter in my 98, our oldmobile runs it and it was handy. I did not notice any real difference except it sucked down a bit more than a quart during it's oil change cycle, usually I loose a 1/2 quart between changes.

0W30 is for winter in Alaska or Siberia.

Been my experience, on the few occasions Eagle has made recommendations and I´ve ignored them and went my own way, I usually ended up where Eagle, tried to steer me in the first place.
Oil recommendations, change with the weather and the age of the motor. Also somewhat bewteen synthetic and fossil oil. Synthetics are usually, if you read close, 30WT. or whatever equivalent, they come out of the bottle thinner than a fossil oil of the same viscosity. Reason being, the synthetic doesn´t thin as much, when hot and/or from shear.
In many of the early (say pre 95) vehicles, synthetic isn´t recommended for the breakin period for a new or rebuilt motor. Some manufactures, have made material adjustments, in recent years and synthetics can be used during breakin periods. A lite synthetic works well for pickleing a motor, for extended storage or as an assembly oil.
In 81 when I orderd a new Dodge pickup with the synthetic oil option, they sent me the motor, with normal oil installed and a package behind the seat with my synthetic, to be run after breakin. Breakin oils are often, some lighter than, the OEM recommendations. A good quality 10-40 or there abouts, usually covers all the bases year round. I ran 5 WT. synthetic in my race truck (after breakin), was a few extra horses.
It´s possible there 0W30 is a true 0W30, in the beginning, Mobile 1 5 Wt was equvilant to 30W fossil. Got too confussing, so they changed there synthetic labeling.

Like eagle said OW-30 oil if for COLD climates. I do not even see why it is sold in the Continental USA - lower 48 in Alaska talk. This a product develope for Canada.

Here is the API oil fact chart, look it over they do not even show OW-30 oil: http://api-ep.api.org/filelibrary/ACF2AD.pdf

In my 88 XJ owners manual it says:
10W-30 for temps 0F and above
5W-30 for temps 60F and below

So even the auto/oil industry have chantged their minds over the years.

At it been said on here the lower "w" number the better the oil flow. In college a guy from the API talked to us and talked about the "energy conserving" program. He told us the ONLY down side to a lower number W is bearing wear. The SAE has a standardized test and comparing 10W and 5W oils the wear on the 5W bearing was 2 or 4 times what it was with the 10W oil.

They guy also said the main reason for the 5W oils was cold weather starts and an attempt to get better gas mileage by the big 3.

What brand and weight of oil people use is "very personal" for some reason. Use the brand you want, use the weight you want. I just recommend you move to Fairbanks alaska to use a 0W-30 oil.

Thank you for four informative replies. I think I'm finally understand oil weiights. I'll stick w/10W40, which Eagle recommended several days ago on another thread.
But Eagle, if the 5W50 you use is 2-4 times harder on bearings, as Martin says, what are its compensating advantages to you?

Bearings rely on pressure, pressure requires flow, thick oils don't flow well when cold. A 0w oil behaves in a very similar manner to a 10w oil at operating temperature, but it has a higher viscosity index, so it doesn't get as thick when cold. Engines don't require a thick oil when starting or starting a warm engine would be disastrous. A good 0w or 5w oil will never hurt an engine if used properly. It's the 30 or 40 number in a 5w-30 or 10w-40 that's most important because that specifies the thinnest the oil will become under normal operating conditions. If you want to look more closely look at the kinematic viscosity at 100°C, which specifies where in the grade the oil is at operating temperature.

I sure like the 5w oils when it gets down to -15°F here in the winter. I definately don't think a 10w is a good choice at those temps, but I know plenty of people that run them. I have a case of Amsoil 5w-40 AFL waiting to go into the Jeep. In general I run 10w oils in the summer only.

Churchlady, Like I said the brand and grade of oil you use is very personal so asking eagle why he does something and use waht I said as your justificaiton is not a good thing. Each of us use what we use for our own reasons. I imagine eagle will say "I have not have a problem with 5W". You know this bearing wear may mean over the life of the engine a few thousand less out of a set main bearings.

Since I have lived in places where the temp did not get below zero F except for a day or two a year I use 10W oil. I also use synthetic and got my mom to use it in chicago. Mom likes how she goes out when it is zero F and her car cranks over as if it is 70F out.

I just picked up 8 boxes of Mobil-1 10W30 at BJ's Wholesale today for $23 a 6 pack, getting near time to do both TJ's and my XJ. I run it all year. If you want to baby your XJ just go with mobil-1 oil and Mobil-1 oil filters or K&N oil filters, you won't regret it... It will spin over just fine at -10 after sitting all nite...

Just to throw something else in the mix. Adhesion properties, the thin/low number, doesn´t stick as well as the thick/high number. And the temp. on your coolant gauge is an approximation, extended high speed runs, can cause hot spots and bearings some hotter than normal running. Oil temp. can be running quit a bit higher than normal, not really indicated by the coolant temp., a slightly higher viscosity, may be benefitial in the long hall. The higher the oil temp. the thinner the oil, coolant temp and oil temp are two different things (though somewhat interrelatted)
Much of the wear in a motor is in the first few seconds after start up, a thinner oil can get to critical points quicker. Many of the internal parts of a motor, run on a film of oil, a very thin oil, doesn´t adhere as well as a thicker oil, accelerates wear.
I typically run a little higher viscosity oil (especialy in the summer), I also regularly drive at triple digits.

I´m with Rich P, I don´t make oil viscosity a religion, a good quality synthetic, depending whats on sale, 10/30 in the fall, 10/40 in the summer and 10/50 when I got a leak (oil lubricates better, on the inside of the motor). Got to say, since I´ve been running synthetic (since around 1980), have noticed cylinder wall wear, on fairly high mileage motors, is minimal. Main bearing wear acceptable. Inside of the motor stays much cleaner. Start ups at - 10 F, a lot easier.

I use Mobil-1 5w-30 year round. I agree with Sparkman wholeheartedly that a 0w or 5w oil will never prove harmful if used instead of 10w. I have seen a couple of oil analysis that indicate M1 5w-30 is slightly below M1 10w-30 in Viscosity index. With all of the moly in M1's new formula I wont lose sleep at night worried that my bearings will spin in the near future. M1 has a new "Race" formula synthetic that costs $10 a quart, the weight is 0w-30.

-Saga

Is there any legitimate benefit to using these "higher mileage" and "specially formulated for SUVs" oils? Other than feeling better?

Figured, they would figure out an additive to enhance the adhesion properties of a lower viscosity oil. Guess it is Moly, I´ve been touting the virtues of moly, especially for high shear gear boxes, for decades. Seems they have gone back to the future and Moly is in again.
Eagle hit the nail on the head, when he said, use a good quality oil and change it often. Extended mileage oils, might hold up well, but the micron sized abrasives floating around in there, still build up.

Kevin said:

Is there any legitimate benefit to using these "higher mileage" and "specially formulated for SUVs" oils? Other than feeling better?

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The high mileage oils are pretty good. I saw a huge reduction in oil consumption with the Pennzoil HM 10w-30 over their regular 10w-30 in a 3.3l dodge. They are usually thicker within the grade and have seal conditioning additives in them. Some are synthetic blends, they may all be I don't know. I don't think they are meant to be used for longer drain intervals.

SUV oils are a marketing gimmick IMO. Mobil 1 SUV is relabeled Delvac 1, their synthetic diesel oil. I am still waiting to find out what makes the oil requirements of an SUV on it's way to the mall any tougher than any other vehicle. IMHO the two categories of engines that work oil the hardest are tow vehicles (certainly some SUVs tow) and high specific horsepower engines (turbo, supercharger, etc). I am not saying these are not good oils, they are just jumping on the SUV bandwagon. If I wasn't running the Amsoil 5w-40 I would probably run Delvac 1 5w-40 (Mobil 1 SUV) or Rotella-T 5w-40.