I have an 03 V6 Accord with 176k on it. I currently change the oil about every 5k, which is less then every 2 months.
This will be my first summer driving through hilly areas to work (83 miles each way highway).
I am considering switching to synthetic.
Please confirm or kill what I have heard about synthetic.

I have heard some claim it helps run the engine cooler.
I have heard there is the potential for better MPG's.
I have heard I could stretch my changes out to 7500 once I am completely on synthetic.
If I do go synthetic I should start with a blend and work my way towards full synthetic.

With the cost of gas any savings in gas would help considering the miles I do.
With the hills I am thinking cooler means less stress on the engine and longer life.

Thanks,
Mark

 

Runs cooler & gets better MPG.
Don't hold your breath. It should be true,but the difference will most likely be very small.

Long oil change intervals.
Likely true. For your own good, you should consider getting the oil analyzed to really determine what your interval should be. Check outBlackstone Labs. You might evenbe OK with 7500mile intervals on good-quality petroleum oil. Then check outbobistheoilguy.com for more information than you ever dreamed of.

Blend in gradually? No.
Most normal synthetics (Mobil-1 etc.)are fully compatible. Go directly to 100% but realize it'll take a couple oil changes before all the residual petro oil has been diluted away. (Just in case you get an analysis done immediately.)

Cold starts are less damaging? YES.
I don't know how cold it gets in winter, but the first 5 seconds after you start a cold engine can be the majority ofit's wear. Synthetic oil will begin flowing nicely, sooner, when it's really cold.

Cheaper in the long run? I have no clue. You gotta do your own math after you figure out the long oil-change intervals.

 

Essentially, there will be no change. 5k is a good interval, but better synthetics can go longer. I will use synthetic after I break the 20k mark because I like the theory behind some of them and I think they are better fluids for the engine.

As far as the other opinions go, the thermostat in combination with the radiator size determine how cool the engine runs, not the oil.
The weight of the oil is all that has potential for changing MPG and since the weight is kept the same, it is a null point. 7500 miles .... not a problem. Dino -> blend -> full synthetic is not necessary. IMO, blends are for the people that want to try synthetic, but are stubborn about using dino oil. IMO, blends aren't any better than regular oil.

My favorites are Amsoil Series 2000 which I have used for a full year multiple times with filter changes twice a year (old filter that I don't think they make anymore, replaced with the nano which is supposed to be good for a year) ..... and Royal Purple. RP has a micropolishing effect that is unique to this manufacturer (The best IMO).

I stopped with the Amsoil only because I changed my mindset on draining contaminents from the engine, not because of any problems.

 

I use synthetic in the S and still change at 5,000 miles. I will switch to synthetic in the Accord after 10,000 miles.

 

markrb,

it is true that your oil does serve to cool the internals as well as lubricating them. saying that synthetics are going to make the engine run cooler by default seems like a stretch, but you will find much information on that if you really want to research it.

overall I have heard that after many miles, SWITCHING to synthetic does not give you enough benefits to justify changing. also, another piece of information I remember from speaking with some engine gurus is that engines have rubber seals that SWELL when in contact with mineral (dino) oil, and that they dont do the same when in contact with synthetic oil. that was supposed to mean that if you switch to synthetic on an older engine, you could end up with some leaks when these seals contract. originally years ago, that was the main reason to do a gradual switch.

that's the sum of MYinfo on that topic. good luck

 

I switched to synthetic in my car when it had ~85K. No leaks, or bad seals.

 

I know rubber seals will swell in certain petroleum distillates. Had that happen to rubber mounting bushings for an in-tank fuel pump.I had them out in the air for a few days (waiting for a new pump to arrive). They were way too small until I soaked them in gasoline.

Anyway, that was a problem when Mobil-1 first came out like 30 years ago. They've put additives in for that problem, but the stories just go on forever.

Sometimes an older engine has seals that are just worn out. But there's just enough crud around it so they don't leak. Until the synthetic oil cleans up the dirt. In THAT case, your seals were already bad.

 

I just like the fact that after 5k miles dino oil comes out black and nasty, while my Mobil1 is dark brown and is still somewhat transparent.

 

Why don't you get a little bit of both worlds and switch to Valvoline Maxlife Synthetic Blend? That's what I use. It has additives that cause the seals to swell. Many debate whether the additives actually work or not, but over on bobistheoilguy.com most of them seem to agree the additives actually work. Regardless, all of the oil gurus over there say Maxlife syn blend is great oil. Plus it costs $12 for a 5 quart jug at WalMart. I change mine every 5k or 4 months.