It seems everyone uses Synthetic oil, mainly so they can extend the change interval. Problem is, Honda states in my 03 owner's manual that "You can use synthetic oil, but NOT TO EXTEND THE CHANGE INTERVAL". I use synthetic, because I think it's better oil, not to extend my change interval. I also take everything Eric the Car Guy says with a grain of salt. He does some things I would not do on my own car.

 

And during a warranty period it might make sense to adhere to what Honda recommends; beyond that...

I use synthetic oil because:

1. Engines start way-way easier in the winter time,
2. Engines typically stay much cleaner internally when run exclusively in synthetic oil, and last but not least,
3. Because I can extend the factory recommended oil change by at least 50% and still have the oil in the engine be in much better condition than conventional which has gone the factory recommended OCI.

 

Doesn't synthetic oil get contaminated, by blow-by, condensation, etc. just as regular oil does over the same mileage? I'm definitely not going 8-10k miles between oil changes.

 

Yes and no.

• Condensation is simply water which will evaporate out the next time the engine gets the oil up to operating temperature. Synthetic oil, by virtue of its more pure carbon chains is extremely tolerant of having some amount of water mixed with it without starting the chemical reactions (typical of conventional oil) which form acid, and if left go long enough will turn the oil "milky".
• A main element of "blow-by" gasses is unburned fuel. As with condensation, synthetic oil is far more capable of holding the fuel in suspension long enough to have it evaporate off.
• The remaining elements of the "blow-by" gasses are combustion byproducts; due to the more pure carbon chains, synthetic oil has the chemical "latches" to hold 50-100 percent more micron sized combustion byproducts (and other contaminates such as wear metals and such) in suspension until the next oil change.

A few compelling points regarding extended oil changes:

• BMW, Mercedes, and Porsche have been recommending 15,000-20,000 mile oil changes (depending on manufacturer and model) for their synthetic oil lubricated engines for over 15 years now; if condensation and blow-by gasses were such an issue, all three manufacturers would have had literally hundreds of thousands of engine failure issues by now.
• If you look over on the BITOG web site you can find literally thousands of Used Oil Analysis reports (UOAs) published there which show quite convincingly that used synthetic oil which has gone roughly 50% longer than the factory recommended OCI, is still good to go and in much better shape than used conventional oil from the same type of engine and vehicle but with fewer miles than the factory recommended OCI.
• I've run a few UOAs on all of my recent cars and the results are compelling to say the least. On a recent report for one of my cars which has a recommended 7,500 mile OCI (and a 15,000 mile filter change interval) showed that the synthetic oil sample I submitted with 12,000 miles on it was in better shape (from both a contaminate and remaining additive perspective) than what they term to be the "Universal Averages" for that car. The funny thing is that the "Universal Averages" showed that the average OCI was just 3,700 miles!

 

Yes, 3,750 miles is what my owner's manual has for "severe" conditions. I was willing to go up to 5,000 miles because my conditions are not all that severe, and I am using synthetic. I guess I saw the long OCIs as owners not wanting to change their oil, and companies trying to lower their "cost to own" figures. I don't mind changing my oil at all, and I'm less concerned with cost to own than how long the engine will last. I'm also a little apprehensive about what a UOA can really tell me about my engine's wear.

 

I dont want an argument but wanna see data when it calls for it.

Yeah I've looked into oil forums and discussions and find them interesting. I'm curious as far as Honda owners go as long as I'm paying attention to this thread. I go 6 to 8k with Synthetic Blend. Don't often have to top off either.

 

I'm not sure I understand that last bit; if all of the wear metals are low, silicone and sodium are low, the viscosity is within range, and the additive package is still registering, then your oil is good to go. If something was wonky with the engine (i.e. something wearing prematurely) then you'd see elevated numbers somewhere along the line in the UOA.

Back in 2005 I had a UOA performed on a vehicle of mine with something over 100,000 miles on the clock and ~11,000 miles on the oil sample, and while all of the metal wear, the silicone, and the additive package numbers came back good, there were two "warning" points; the fuel percentage was near the upper limit of 2% and the sodium numbers were several times the limit.

At the next oil change (also at ~11,000 miles) I sent in another sample, the only difference between the two samples was that instead of cold starting the engine and driving a couple of miles to partially warm the oil, I did the oil change immediately after running fifteen minutes or so on the highway. The sodium came back high again (as expected), however, the fuel percentage numbers came back at almost zero (as hoped).

As I was unsure where the sodium was coming from (coolant via the head gaskets was the number one candidate), I switched to propylene glycol from ethylene glycol to protect the engine bearings (the UOAs were still showing good tin and lead numbers, but ethylene glycol is bad-bad for bearings), while I figured out how the coolant was leaking into the oil. The following summer I pulled the heads and unfortunately I found no "smoking gun"; not surprisingly the coolant consumption (which I had since measured at roughly one ounce per 17 hours of operation) continued unabated.

After more research I found out that this particular engine was known for developing small coolant leaks past two twenty cent "O" rings in the timing chain cover (through which there was a coolant cross over canal); I replaced the "O" rings and BINGO!, the coolant usage stopped and the next UOA came back with all numbers well below (or above if "higher is better") than the universal averages.

So, one might say that R&Ring the head gaskets was a waste of time and money. Yeah, well, not exactly; I got a chance to see the internals of the engine after over 140,000 miles of driving on extended oil changes. The engine was perfectly clean, the cam lobes looked perfect, and believe it or not, the factory honing marks were still on the cylinder walls of all six cylinders. The engine had over a quarter of a million miles on it when I traded the old girl in and at the end it was still consuming roughly a quart of oil every 8,000 miles; just like it did the day I drove it off the showroom floor. Not too shabby.

Long story short, you'd be surprised what a UOA can tell you about the internal health of your engine.

 

I don't seem to loose a drop between changes, but then it's only 5000 miles (Mobile 1).

I guess I'm just skeptical, but rather than pay for multiple UOAs, and adjust to whatever they say, I'll just change my oil every 5,000 miles and hope for the best. It's been working out OK so far.

 

You will have to make the decision to switch from regular to synthetic oil. If you make the switch, closely monitor your oil level.

I personally found that my oil level doesn't drop nearly as fast with Castrol Edge with Syntec compared to Mobile 1.

You will get a ton of arguments about brands, viscosity, etc..

Use only the recommended viscosity in the owner's manual. I am not a fan of changing the oil viscosity unless you live in an extremely warm or cold environment an you need a different viscosity for the temperature (this will be shown in the manual too).