Not to be argumentative, BUT:

The first 1500 mile oil change is critical to getting the metal shavings out of the oil, which are bad for the system but are not going to choke the engine down. It's not going to likely matter much, but who wants those little metal shavings in there increasing friction and reducing mileage? No one does.

And on the MPG effect of synthetics, that entirely depends on the engine and the oil used. I went from Dino 10w30 in a 1997 Suburban to Amsoil 0w30, and I got a MPG increase from 17 mpg to 19 mpg, which is not much, but is actually a 12% increase. The effect will not be noticable in some cars, but what WILL INDEED HAPPEN NO DEBATE is that the engine friction will be reduced, which reduces the oil and engine temps and helps the engine in the long run. Synthetics reduce friction over dino oil because their molecules are uniform in size and the oil is "slipperier" if that's a word.

It's a personal decision to make, and there are millions of cars who have gone 150K with using Dino oil. But those same cars probably could have gone 175K or 200K had they used Synthetic oil all those miles. Synthetic oil is not a gimmick or a scam - it's actually BETTER OIL and anyone who cares about their car would be wise to use it.

Not taken as argumentative....it is a personal decision. However, given the total miles I'm getting with my cars, it can't be that critical.
That is a substantial increase in mileage you got by switching, but it goes against my experiance and every (independant) study I've read....but I can't argue with your own experiance. If I got anywheres near that increase, any increase, I would most definitly be using synthetics also.

Prius owners report slight MPG increase w/Synthetic:

http://john1701a.com/prius/prius-advice02.htm

And about studies - that's a stumper for sure. The problem is, no one will sponsor a study which will prove that Synthetics are better because a) who's going to do that besides an oil company, and thus you lose the independent part, and b) the government does not want to make any of the large oil companies mad by proving it either way. If they say Synthetic is better, then it will force a big change in the whole oil/auto industry, maybe putting pressure on the car companies to use Synthetic in all new cars, which would cost them lost profits. So it's a lose/lose scenario to have Synthetic oil be shown superior.

But MPG is only PART of the benefits of synthetic oil. It also protects better at high temps and high rpms, and coats better thus protects better at startup.

Anyway, I think my points have been made. Use Synthetic oil for many reasons besides a potential MPG gain.....

I'm not very familiar with how they make synthetic oil, but if everybody used it, wouldn't we save a lot of real oil for other uses?

Rich

My dealer in Princeton, NJ said the orig oil change should be at 7500mi(a lot but makes sense).
Then he told me that the regular oil changes should be at 3750 or so. The reasoning is that the engine stop feature at lights now. This results in severe (stop and go style) duty on the oil and as a result it needs the changes often. Also makes sense.
I do plan to eventually go to synthetic (Amsoil) with guidance of oil analysis. More later.

You'll love this one...when I bought the car I inquired about dealer oil changes and asked what type of oil they used in the service bays...the reply...Quaker State. I believe he was serious...and this is a very large and very reputable Honda dealership. Needless to say, I decided to forego the "service plan" and just do my own when the time comes.

Any "metal shavings" circulating with the oil are removed by the oil filter. That's what it's there for. Yes, there are smaller particles (microscopic) that the filter won't pick up, but those are also smaller than the clearances in the engine, so aren't causing friction and lots of wear. Also, engines are pretty much spotless when assembled. There aren't a bunch of visible metal shavings, turnings, etc. in there. If that stuff was there, filter or not, the engine would be destroyed on its first start up.

Contaminants, including from metals, are high when the engine is breaking in, of course.

It's also true that Hondas do have special break in oil. It's apparently high in Molybdenum additives for break-in purposes. People have had oil analyses performed to find that out. Consensus on other boards seems to be to leave it in there for at least 3K miles or so.

The reason for the 3750 oil change is fairly clear on the HAH. I stated before it is due to the "Auto Engine Stop" feature.
Whenever you start and stop and engine you get some unburned combustion products remaining in the cylinders and the MAIN reason is that to start the engine the fuel is enriched slightly (to better start combustion) on starting, sort of Choke action, except it is done with the injection.
This gradually contributes to increased fuel "blowby" down the cylinder walls and into the oil. Fuel dilution is very difficult to get rid of since it isn't filtered out and eventually thins the oil and reduces its lubrication properties because gasoline (vs diesel fuel) does not lubricate.
That is why good oil analysis has a fuel dilution percentage.
Even synthetic oils, or additives, cannot overcome the fuel dilution problem although they are usually better lubricants. Also the engine cools slightly when stopped and increases some other types of oil contamination.
These sort of problems always occur with stop-and-go driving and most manufacturers consider stop-and-go as severe duty on the engine oil.

I plan to do an oil analysis at the recommended change interval, after I have driven some typical miles based on my driving practices. I want to see how much of a problem this will be.
If I need to change as recommended I will likely use dyno oil as synthetic cost would be high. Good dyno oils work well but usually don't have as long a life which makes little difference when changing at 3750 miles.

The only way an HAH driver could plan to reduce fuel dilution (or stop-and-go duty) is by 70+% highway driving and thus greatly reducing the HAH's "Auto Engine Stop" activity.

Honda claims in the manual and website that they add 'stuff' to the factory oil to help engine break-in. Somewheres in this forum someone posted their oil analysis results from the 1st oil change, at around 7500mi. There IS stuff in the oil- molybdenum, I think? As I recall in the thread, nothing exotic that you can't add yourself at any time. Honda is not just blowing smoke. I can't speak as to exactly what Mo does for the engine, however.

I fear to tread further into the oil-change-interval wars. It's almost like religion or current politics- quite polarized, eh?

That is one reason why the interval is 7500, the engine doesn't run for all of those 3750 miles! (And moreso if you reboot alot.) I don't think that IMA actually uses the standard "crank and fire" type of methodology to start the engine, especially after reboot. Because the IMA is "cranking" the engine (at a far higher speed than a starter), the need to have an ultra high rich fuel mixture is alleviated.

-Charlie...