Best Oil for MPG - 8.7% increase?

Kate great info'. I also found this on 0W-20

http://www.iantaylor.org.uk/papers/AsiaFL2002.pdf

seems like it does make a big difference to the power delivered too - around 10%+ - and also mileage.

Some caution - use the oil your manufacturer recommends only.

Apparently people in Europe went gungho on syntechtics and many ruined their engines. Mercedes just had a $235m class action here in US for not issueing clear warnings.

I'm sticking with Honda 0W-20 now that I read all this - I just got 5 Q for $15+ from my dealership - and I plan to change ever 5,000 miles.

So what was the problem with Mercedes ? All their cars come with and use Moble 1.

I seriously doubt there was "no warning". It was probably worded a lot like Volkswagen though, which also has actually paid to replace people's entire engines due to sludging up when using conventional oil instead of synthetic. In VW's case, the manual states something like "Required oil: VW 502.00" which just happened to be a synthetic oil.

Most people blew it off and assumed that if the manual says they can do oil changes every 10,000 miles on VW oil, that means they can do oil changes every 10,000 miles on Wal-Mart 99-cent oil too. Fact is, that's just not true. Synthetic oil really does offer longer life and greater protection than the cheap stuff.

As for me, I've decided to start having my oil analyzed so I can get a better handle on exactly what the wear characteristics are for various intervals of oil changes. If you check out Blackstone Laboratories ( http://www.blackstone-labs.com/ ) you'll see that for $20 you can have oil samples checked out to determine the quality of the oil and an idea of what's going on inside your engine. It appears to be pretty worthwhile for those of us that intend to keep our cars running a long time while also trying to get as much time between oil changes as possible before the oil breaks down.

I have been putting Mobil I or Syntec 5W-30 winter and 10W-30 summer in our Subaru and at 94K miles it runs great and does not burn any oil.

I change it twice a year. We put about 10K miles on each crankcase of oil.

I have also discovered that super premium gasoline gives superior mileage but not better economy. I suspect the higher octane means the knock sensors allow maximum advance.

99% of the time we run regular but there is a difference with Sunoco 94 altho hardly worth the expense.

The numbers on oil are SAE (Society of Automotive Engineers) ratings that indicate the viscosity charateristics of oil. The first number indicates the viscosity at STP (standard temp and pressure - about 70 F and atmospheric pressure) and the second the visocsity at operating temperature. In other words, for a 0-30W oil, it will be as viscose as a straight 0W oil at STP and as viscose as a straight 30W at engine operating temperature.

The thing is -- most hybrids are Akinson cycle engines and they run cooler than Otto cycle engines, so high temperature protection is less critical in hybrids, in addition to the lower compression and blowby charateristics of an Atkinson engine which means the Atkinson is less demanding on oil than a comparable Otto engine.

Full synthetics, like Mobil 1 or any equivalent oil, are ALWAYS a better choice than conventional oils. However, the conventional 0-20W oil is a good oil and it is unlikely that either choice will mean much of a difference in total engine life. The big destroyer of engines, dating back to the days of Henry Ford, were lead oxides. Since the tetra-ethyl lead was removed from gasoline (1975) and engine life has increased 3 and 4 fold at least. Compression ratios were also lowered to reduce nitrogen-oxide emmissions and that also reduced wear. In other words, most modern engines are good for 300,000 miles AT LEAST with the exception of parts that have nothing to due with the engine oil, like timing belts, water pumps, etc.

For some engines, this decrease in corrosive element formation exposed vulnerabilities in engine design which were not obvious in 1964 (because the rings and valves were shot within 75,000 miles because of lead oxides). Now, the poor upper engine lubrication and the poor oil galley designs of those 1950s and 60s V-8s become the mode of failure rather than worn rings, valves and valve guides. Jeeps are still equipped with the Chrysler 318, 340, 360 series V-8s, and equipping them with fuel injection and a computer controlled engine management system did improve operating charateristics but did not improve the limitations of the basic engine design.

Synthetic oils WILL increase FE, but only by a small amount. Still, for those of you changing incandescent lamps over to LEDs so as to reduce electrical loads so as to increase FE, a synthetic motor oil is a good choice. Make several small gains and they add up. Synthetics are expensive but the drain intervals are also doubled, which levels the cost. For a Ford Escape, where the recommended drain intervals are 10,000 miles, you increase the drain interval to 20,000 miles when running full synthetics.

Why do we change oil, anyway? Because the engine produces contaminants that can erode critical engine parts, like bearings. There are additives in motor oil that neutralize those contaminants. Those additives become exhausted and the oil needs to be changed to replenish the additives and flush out the contaminants. By the way, the same reasoning applies to changing coolant. So, if you want to avoid head gasket leaks and other critical corrosion, change your coolant to replenish rust inhibitors and other anti-corrosion additives and flush out corrosive elements. I consider this more important that engine oil, if engine life is your concern.

Now, oil also breaks down into smaller molecules after awhile but the combination of the reduction of lead oxides, nitrogen oxides and other contaminants due to the change in gasoline formulation and lower compression ratios mean that drain intervals can be increased for any oil, and especially for synthetic oils which have superior lubricating charateristics along with superior operating stability.

There is no wrong choice between 0-20W conventional oil, a partial synthetic or a full synthetic -- either 0-20W or 0-30W. I use 0-30W Mobil 1 full synthetic and double my drain intervals. I have an 18 year old Saturn SL-1 with 205,000 miles and I just sold my 1999 Taurus with 254,000 miles to buy a FEH (which I LOVE). My wife has a HCH and we do the same for her.

By the way, mileage studies that are published on this oil or that oil are all flawed in their published "conclusions." A difference in the stated increase in FE achieved is based upon the difference in means (averages) and is only significant if the standard deviation is known, not just the difference in means. In other words, if a t-test is applied there would be NO STATISTICALLY SIGNIFICANT INCREASE IN FUEL ECONOMY WHEN COMPARING 0-20W CONVENTIONAL WITH 0-30W FULL SYNTHETIC oils. There might be a difference between a conventional 10-30W conventional oil and a 0W-20W synthetic, but it would be probably be a marginal t-test outcome and be dependent upon the driver's use of the vehicle and their driving characteristics.

None of the posters in this blog have made bad choices. Everyone has made good choices and will be happy with the results they are achieving. The real story here is the Atkinson cycle engine, not the motor oil inside of it. If anyone tries to convince you otherwise they are expressing an opinion. If they claim to have data, examine the standard deviations and apply a t-test at a 95% confidence interval.

You have all made a good choice with any oil that is 0-xW conventional or synthetic. Enjoy your hybrid vehicle. I enjoy mine (and my wife's).