Have you ever heard of this oil? It seems so hard to find…
Also, maybe a SDoper can review what the figs mean and extra credit - how come some oils will say “W40 motor oil”, IIRC? What’s up with that?
IIRC, I know these figs express viscosity in relation to temp…
These ratings are maintained by the American Petroleum Institute. Look for the API logo on the can.
5W40–the oil has additives that give it the viscosity of a straight grade 5-weight at 0[sup]o[/sup]C. It has the viscosity of a straight 20-weight at 100[sup]o[/sup]C. Basically, it flows better at low temperatures than it would without the additives (though there is a slight loss of shear strength, IIRC.)
According to Honda, my 2003 CR-V is supposed to take 5W-20, which IS hard to find. Some rooting around in various on-line Honda fora revealed that the more common 5W-30 is perfectly fine for my car, and perhaps even better at preventing long-term wear. The reason that Honda says to use 5W-20 is that it provides an infinitessimally small increase in gas mileage (as in just tenths of a m.p.g. more). It’s not enough for the individual owner to notice, but when factored over the thousands of copies of the vehicles sold, it allows Honda to meet its CAFE (Corporate Average Fuel Economy) standards defined by the government.
Ford and Honda started pushing 5W20 motor oils for most of their new cars, and some of their old ones in about 2001.
Ford’s stated reason for doing this was to increase fuel economy.
Ford has a special standard for the performance of the oil to be used in its newer cars that have 5W20 specced. Interestingly, this standard is fairly demanding so far as thermal breakdown goes.
I’ve never seen good, hard evidence that 5W20 will cause more wear than 5W30 would in engines wherein the automaker has reccomended it, and I’ve researched this to a fair degree.
I had seen some circumstancial evidence and trending that may show greater metal wear numbers for 5W20 than 5W30, but absolutely nothing you could really prove.
5W20 is tricky to find if you buy your oil at supermarkets, gas stations or smaller general purpose retailers.
I can find 4 different brands at my local Wal-Mart.
I can find 5 different brands at my local Auto Zone.
I can find about the same number of brands at Advance Auto.
As a last resort, if you really can’t find a 5W20, ask for bottled Motorcraft 5W20 at your local Ford/Lincoln/Mercury dealer.
Regarding your question as to what the left and right side numbers in an oil’s viscosity designation mean, Texaco has a surprisingly helpful page discussing what the various oil grades mean, although it lacks an extensive discussion of 5W20. <1>
I will sum up some of the various grades available:
0W30: popular in Europe as a synthetic for extended drains. Works in basically any climate. Good down to about -30 Fahrenheit.
5W20: Popular in the US and Canada with Ford, Mazda, Honda, and Chrysler [beginning this model year]. Not widely used outside of North America. Good down to about -20F.
5W30: The most widely reccommended oil in North America. Good down to about -20F.
10W30: The oil your carmaker may reccomend for your nominally “5W30” car if you’re operating it in hot conditions. Incidentally, in conventional oils, this is one of the cheapest grades to make. Good down to about -10 Fahrenheit.
10W40: Widely reccomended a few years back. Probably obsolete in North America unless being used as a band-aid on cars that use oil, or in racing. Good down to about -10 Fahrenheit.
15W40: A grade generally used in combinations with diesel-engined trucks and buses. Good down to about 0 Fahrenheit. Lots of stoud blends here, tends to be more pricy than 5W30, etc.
20W50: Probably obsolete in North America unless being used as a band-aid on cars that use oil, or in racing.
SAE 30, Non-Detergent: Mostly for lawnmowers and other non-vehicular beasts.
SAE 30 HD (Heavy Duty): Used in certain diesel engines in place of 15W40. There’s a Detroit Diesel 2-stroke model that has problems without SAE 30 HD. Good down to freezing temp of water.
Miscellaneous other oddities include 0W40, 10W60, 15W50 and 20W20, SAE 10, SAE 20, SAE 40, SAE 50.
It’s also important to note that, contrary to popular opinion, all motor oils have more viscosity at lower temperatures and less viscosity at higher temperatures.
I think the original question has been answered, but just wanted to throw in my 2 cents here. Whenever I can find it, I always use a synthetic, 5W50. I figured, no matter what I encountered, I had it covered. Can be a little tough to find, tho.
IMO this may not be a wise thing. Is it a newer vehicle? If so, the oil is probably too viscous at high temperatures. Continued usage of this oil will decrease the life of your engine. It would be better to use the type of oil recommended in your owner’s manual.
In Minnesota, with a car like yours, I’d consider running a synthetic 0W30, 5W30, 0W40, or 5W40.
If you ever see temps below -20 Fahrenheit, amend that to synthetic 0W30 or 0W40.
If you’re within your new car warranty, make sure that whatever you put in is consistent with the manual until the warranty expires.
Just thought I’d add how multi-viscosity oil works. Long chains of synthetic molecules are added to it. At low temperatures these molecules remains tightly ‘wound’ thereby not hindering flow (i.e. not increasing viscosity). As the temp increases these chains begin to ‘unwind’ and restrict flow making the oil thicker as the engine gets hotter (which is what you want).
The reason you don’t want to have too wide a range (w/o using a synthetic oil) is that you’d have to start with a very thin oil and add a lot of these molecular chains in order to get a thick enough high-temp viscosity. And these additives chemically breakdown quicker in larger quantities.