Since this has gone downhill, perhaps a few quotes from the article are in order to illustrate the salient points I found interesting, especially since some have obviously not bothered to read. Anyone up for some discussion?
Originally Posted By: article
Conventional wisdom states that engine oils that increase fuel economy allow less friction and prolong engine life. The purpose of this article is to challenge conventional wisdom...
Ok so we know where this guy is coming from.
Originally Posted By: article
Fuel Economy: Does Anyone Really Care?
First, we should face the fact that the American consumer does not typically care about fuel economy except during difficult economic times. The No. 1 selling passenger vehicle is the Ford F-Series Pickup. Five of the top 10 best-selling vehicles are trucks, and trucks outsell cars.
Some of the trucks are called sport-utility vehicles, otherwise known as SUVs, because their owners don’t want to admit they are trucks. The mass (size, weight) of these vehicles is not conducive to great fuel economy.
There have been numerous posts about soccer moms in Escalades. This is a fair point. Now if 40mpg+ vehicles were top sellers his argument wouldn't hold water.
Originally Posted By: article
Thinner oils are being used these days for three reasons: They save fuel in test engines, the viscosity rules have changed, and manufacturers are recommending thinner grades.
The Sequence VI-B is the test used to evaluate fuel economy for the GF-3 specification. The VI-B test engine is fitted with a roller cam where the old Sequence VI test used a slider cam. The old Sequence VI test responded well to friction modifiers, but the Sequence VI-B responds to thinner oils.
The test oil’s fuel efficiency is compared to the fuel efficiency of a reference oil in the Sequence VI-B test. To pass, the test oil must improve fuel economy one to two percent, depending on viscosity grade. SAE 5W-20 must produce higher relative fuel efficiency than SAE 5W-30.
It is interesting to note that the reference oil is fully PAO synthetic SAE 5W-30. To qualify for the GF-3 Starburst, ordinary mineral oils had to beat the fuel economy of the full synthetic reference oil. (It seems there is more to fuel economy than a magic base oil.)
Although the GF-3 specification is outdated in the US, the concepts here are sound IMO. Sounds like the test has been altered to favor thinner oils; I don't have the background to comment on the testing regimens, perhaps someone in the industry can put up some enlightening information.
Originally Posted By: article
Because of the change in cold-flow requirements and the fuel economy test pushing formulators toward the bottom of the viscosity grade, today’s SAE 10W-30 oils are more like yesterday’s (GF-1 spec) SAE 5W-30 oils. On top of that, there is a trend toward auto manufacturers recommending thinner grades. This seems ridiculous. SUVs and trucks, with their inherently less-efficient four-wheel drive and brick-wall aerodynamics, need powerful, gas-guzzling engines to move their mass around in a hurry. In response, auto manufacturers recommend using thin oils to save fuel. Incredible!
Another good point...putting a more fuel efficient grade in a low mpg vehicle to save gas.....
Originally Posted By: article
Thinner oils have less drag, and therefore less friction and wear. Right? Perhaps in the test engine or engines that experience normal operation. But somewhat thicker oils may offer more protection for more severe operations such as driving through mountains, pulling a boat, dusty conditions, short trips, high rpm, overloading, overheating and overcooling.
Any abrasive particles equal to or larger than the oil film thickness will cause wear. Filters are necessary to keep contaminants small. The other side of the equation is oil film thickness. Thicker oil films can accommodate larger contaminants.
This backs up the Toyota owner's manual suggestion to use heavier oils for towing, continuous high speed, etc. Also backs up what BITOG already knew: filtration is important.
Originally Posted By: article
Temperature has a big effect on viscosity and film thickness. As a point of reference, one SAE grade increase in viscosity is necessary to overcome the influence of a 20°F increase in engine temperature. At a given reference point, there is approximately a 20°F. difference between viscosity grades SAE 30, 40 and 50. SAE 20 is somewhat closer to 30 than the other jumps, because SAE 30 must be 30°F higher than SAE 20 to be roughly the equivalent viscosity.
In other words, an SAE 20 at 190°F is about the same kinematic viscosity as an SAE 30 at 220°F, which is about the same viscosity as an SAE 40 at 240°F. This approximation works well in the 190°F to 260°F temperature range. One might be surprised at the slight amount of difference between straight viscosity vs. multiviscosity oils with the same back number (for example, SAE 30, SAE 5W-30, and SAE 10W-30).
If an SAE 50 oil at 260°F is as thin as an SAE 20 oil at 190°F, imagine how thin the oil film becomes when you are using an SAE 5W-20 and your engine overheats. When an engine overheats, the oil film becomes dangerously thin and can rupture.
I thought this interesting.
Originally Posted By: article
As wear increases, the efficiency of an engine declines. Valve train wear slightly changes valve timing and movement. Ring and liner wear affect compression. The wear hurts fuel efficiency and power output by an imperceptible amount at first, but then the difference in fuel economy between an SAE 10W-30 and SAE 5W-20 is hardly noticeable. Efficiency continues to decline as wear progresses. Perhaps optimizing wear protection is the way to reduce fuel consumption over the life of the engine.
Although thinner oils with less antiwear additive outperform more robust products in the 96-hour fuel economy test, it is not clear that such products save fuel over the useful life of the engine.
Something I hadn't thought of at all, might make an interesting discussion.
Originally Posted By: article
The best protection against wear is probably a product that is a little thicker (such as SAE 10W-30 or 15W-40) and has more antiwear additives than the oils that support the warranty. The best oil for your vehicle depends on your driving habits, the age of your engine and the climate you drive in, but it is not necessarily the type of oil specified in the owner’s manual or stamped on the dipstick.
Originally Posted By: fdcg27
This is a perennial topic here and the article you've linked to has been linked to in earlier threads as well.
My takeaway after years of information and thought is about what it was long before I came here.
To wit, most engines as most of us use them are perfectly fine on a variety of grades.
Whether a thicker grade would reduce wear with our two current daily drivers is a valid question, but also a pretty irrelevant one since any decent modern engine throws off so little metal after break-in.
There are special cases where a thicker than recommended grade might be appropriate for all users, but those aren't typical.
There is no doubt that you'll do no harm in using a thicker than recommended grade and may do some good, so those who wish to do so should go right ahead. The loss in fuel economy will be only slight and the thicker viscosity at really low temperatures will only matter in areas where the engine should have some sort of pre-heater used anyway.
It's all a matter of what you've come to learn and therefore believe.
No oil can really make up for baked-in design or materials selection problems, though. Soft cam lobes, piston slap due generic sized pistons as well as inadequate skirt length and timing chain wear due to inadequate hardening are all known problems with certain current engines that no oil can fix.
My apologies for missing this, you must have posted while I was typing mine. I didn't know this article had been posted before, or I wouldn't have put it up. Thanks for the perspective and intelligent response.
