[enkeivette]

My UTI buddy told me that the w stands for winter, not weight. So if 10w 30 means 10 winter, 30... I'm confused. Obviously the higher the number is, the thicker the oil, but then why would it be 10 winter? Not 30 winter? I would think 10 would be the hottest temp viscosity and that the oil wouldn't get thicker than 30 during the winter.

[94cobra69ss396]

Originally Posted by enkeivette

My UTI buddy told me that the w stands for winter, not weight. So if 10w 30 means 10 winter, 30... I'm confused. Obviously the higher the number is, the thicker the oil, but then why would it be 10 winter? Not 30 winter? I would think 10 would be the hottest temp viscosity and that the oil wouldn't get thicker than 30 during the winter.

He is correct. I got this from Castrol's website:

The API (American Petroleum Institute) symbol on motor oil labels is also called a donut. It unlocks a lot of cool and critical information that can help you choose the ideal motor oil. Let's nibble away at the donut to understand its true meaning.

Top of the Donut – Performance Level Indicators
See the two letters at the top? The first signifies engine type. If you see an "S," that oil is designed for gasoline vehicles. A "C" means diesel. The second letter represents quality. For the most protection from power-robbing deposits watch that second letter. The higher it is, the higher the performance quality. "SM" is tops for gasoline engines.

Center of the Donut – Viscosity Grade Identifiers
Right in the middle is where you can focus on viscosity, which relates to oil flow at different temperatures. Look for the SAE (Society of Automotive Engineers) mark. The lower the number on the left, the thinner the oil at low temperature, and the happier your engine will be in cold weather when it's time to turn over. The number to the right relates to higher temperatures. Higher numbers indicate thicker oil for better performance in the heat. The "W" stands for Winter Grade.

Multi-grade oils carry a dual-viscosity grade so they perform well in high or low temperatures. Now when you see identifiers such as 10W-30, 5W-20 or 20W-50 you'll know what it means – winter on the left (go lower), summer on the right (go higher).

Bottom of the Donut – Energy Conserving Properties
Down below, oils with fuel-saving ability that pass standard industry tests are labeled as Energy Conserving. With rising gas costs, it's nice to know if your motor oil also provides fuel economy benefits.

[Vettezuki]

The old guy (forgot his name) who owns this company will absolutely talk your ear off about the history of lubricants/oil and how much "snake oil" is involved in the marketing of said. Especially American made Mobil One synthetic. As I recall the main thing is that while it's highly temperature resistant, it easily becomes very acidic and causes premature bearing ware. Talk to him and you'll get an earfull of TBN this and Ph balance that . . . be prepared. I should have taken notes, because it's gone a bit fuzzy.

http://www.gopurepower.com/

The bottom line here for most of us, about the best oil you can get before going to the custom Gucci blended stuff is cheap and easy Rotella (Shell) 15/40. If you buy it in a 5gal drum it's less than $3 a quart.

[enkeivette]

But why would the oil be thinner (10) in winter temps than in summer temps (30)???

Ben, very interesting. You run cheap organic Shell oil? I'm a firm believer in synthetics, but I have heard some negative things about Mobil 1. I might go with Royal Purple or Redline in the vette after break in. I put so few miles on it I could prob change the oil once a year without it getting dirty, and I've heard that synthetics don't break down after time, so mileage is more important than the length of time it sits in your oil pan. Right now I'm using Valvoline.

[Vettezuki]

Originally Posted by enkeivette

But why would the oil be thinner (10) in winter temps than in summer temps (30)???

Ben, very interesting. You run cheap organic Shell oil? I'm a firm believer in synthetics, but I have heard some negative things about Mobil 1. I might go with Royal Purple or Redline in the vette after break in. I put so few miles on it I could prob change the oil once a year without it getting dirty, and I've heard that synthetics don't break down after time, so mileage is more important than the length of time it sits in your oil pan. Right now I'm using Valvoline.

There is no such thing as synthetic oil per se. It's processed from natural oil. Mobil One (American) is just about literally made from paraffin as I recall. Yes I run the cheap industrial stuff and maybe change a little more often. The engine runs noticeably a bit smoother and quieter (rockers are less noticable). But as the old timer described the important factors are things like quantity of TBN (as I recall) and the actual ph balance of the oil, these are the actual lubricating and non-wearing petro-chemical attributes you need to be concerned with. I'll need to hit him up again, or find actual tech articles.

The winter summer thing is really only a short hand for thermal viscosity (weight @ temp); it corresponds to objective viscosity within objective temperature ranges, the details of which I don't recall. Dig through SAE docs for gruesome detail somewhere. YES, the multi-grade oil gets "heavier" as the molecules unwind with temperature. Easier for startup, heavier protection for operation.

Here's a quick easy read (just scanned) on weights.
http://www.aa1car.com/library/oil_viscosity.htm

Sorry I can't be precise, I remember "about" the issue but not the details.

[enkeivette]

Very skeptical of this, I'm not a chemist but I can tell you that hot oil is thinner than cold oil. I've seen & felt them both.

[kdracer73]

Originally Posted by enkeivette

Very skeptical of this, I'm not a chemist but I can tell you that hot oil is thinner than cold oil. I've seen & felt them both.

I totally screwed that up !! Had not had my coffee yet. Had to delete it to hide my shame . .

[Leedom]

Nice short explanation. How Stuff Works!

[SeanPlunk]

What kind of oil is everyone using?

I used Mobil 1 on the Camaro, but I'm using Royal Purple on the Cobra now. I've thought about using Amsoil next time though. Opinions?

[SeanPlunk]

Originally Posted by kdracer73

I totally screwed that up !! Had not had my coffee yet. Had to delete it to hide my shame . .

LOL, don't feel too bad - I brought two left shoes to work today