It's funny with the petroleum industry using their own viscosity scales, but here's an attempt. I might be a bit off with the numbers, some stuff is visually evaluated on graphs. I don't work in the petroleum industry, so I'd have to do more digging to get better numbers.

SAE-20 engine oil covers about a +/- 25% range of viscosities & still can be called "20".

At 20deg.C, that SAE-20 engine oil has viscosity 180 times greater than 20C water.

Oils will thin out much more with temperature compared to water.
Going from 20C to 100C, water viscosity will decrease by x2.3, and oil will decrease by x8.2 so their viscosities will get closer together. At 100C, the oil will be about 50x higher viscosity than 100C water. In fact, the 100C oil will have viscosity about 22x higher than room-temperature water.

Multi-grade oil "0w-20" will have less change with temperature, but still it'll be much thicker when cold than it is when hot. So maybe at 20C, the oil is 50x higher than water, instead of 180x for the straight SAE-20 oil.

 

Edit: misunderstood Poorman's statement. I thought he said the hotter it is the thicker the oil gets. He must mean that when it's hot, use thicker oil. When it's cold, use thinner oil....

 

Thanks for all the response. Based on what I've been reading in this thread, it seems as though using 0W20 or 5W20 synthetic will have no ill effect on the new Accord's 2.4L engine. Certainly Honda would not recommend any oil that would be harmful but I just wanted your opinions.

Now, Honda recommends using their brand oil (of course); however, I've never had any problem using Royal Purple in the past. Royal Purple now makes a 0W20 oil so I'll need to do some economics to see which one costs more to use. I plan for oil/filter changes at around 7,500 miles using synthetic. My gut feel is that RP will cost a little more, but it's a very good synthetic oil. I'd use either RP or Honda filters.

If I go with Honda oil, I'll just let the dealer change it - providing he uses the 0W20 Honda oil. FYI, one Honda dealer in the Houston area advertises natural grade Pennzoil but that dealer is owned by the Roger Penske group. (I believe Pennzoil partially sponsors Roger's race teams.) If I go with Royal Purple, I'll find a local garage to do the change and I will provide the oil, filter, and crush washer.

If you have any opinions on Royal Purple vs. Honda oil/filters, let me know.......and thanks again for your previous replys.

 

Oil certainly gets thinner when it's hot, thicker when it's cold. Take a bottle of oil put in a sink & cover it with HOT tap water, leave it sit long enoug for the oil to get hot all the way through. Put another bottle in the freezer. (Don't let your wife catch you...) Watch how they pour.

Water & nearly all liquids get higher viscosity as they get cold But oil has a much stronger behavior that way, than water.

Multi-weight oil 5w-20 or 0w-40 still gets thicker when it's cold, but it just doesn't get SO MUCH thicker. So for example, SAE-20 (straight-weight) might get 8-times thicker when it's cold. But SAE 0w-20 "only" gets 2 or 3-times thicker.

Oil industry is stuck with those old "weight" numbers, which encompass the behavior of thickening when cold. So a 0w-20 oil measures like an SAE-0w oil if you measure it cold. But the same 0w-20 oil measures like an SAE-20 oil if you measure it hot.

I like the Bowie quote! Fluids (viscosity etc) is part of my stuff (thermal/fluids enginer) but I just don't work in automotive or petroleum industry.

 

OK, Tenbrooks...

Yes, the weight 0w-20 or 5w-20 will be fine. Does Honda now call for synthetic specifically? Does it have any other specification number besides just saying "synthetic"? My newest Honda is 2007 Civic, and it simply calls for API-SM or something like that, which means petroleum is OK.

 

Honda doesn't call for synthetic; but, says it can be used if it meets the same requirements given for a conventional oil. But, it is far easier to find 0W-20 and 5W-20 in synthetic than conventional oil at stores like Walmart, etc. Honda calls for API (American Petroleum Institute) premium grade detergent motor oil, which has the API certificate seal.

 

I've been using Castrol GTX for ages in quite a few different Hondas, & Walmart always has 5w-20 in stock around here. Oil analysis says it's still good after the oil-life monitor gets to 10% in the 2007 Civics.

 

Hmmm... I guess I have not been looking in the Castrol oil section. I used conventional Castrol exclusively for ages, then switched to Mobil 1 synthetic years ago. I've only seen Mobil 1, Pennzoil synthetic, and Castrol synthetic in those weights at Walmart; I must not be looking hard enough at the conventional oils.

 

Walmart seems to have different stuff in different parts of the country. I used to see Mobil1 0w-40 which I need for the Saabs, but they don't have it any more. Other Saab people are still finding it at THEIR walmart stores.

Redbull, do you know if that's still the case for 2012 Honda? They've changed their oil specs a few times over the years. For all I know, they have a new spec.

 

The 2012 is still just calling for API premium grade oil. Conventional oil is fine. I use synthetic due to the high mileage I can accumulate in a short time, sometimes close to 2,000 - 3,000 miles in a month, so I want a little longer oil change interval.