How long in between oil changes with synthetic?

[TurboDan]

What the title said. 

I've heard tons of different opinions on this. Some people stick to 3K just like with regular oil, but they must have some pretty deep pockets. As for me, I drive a lot of miles, but the vast majority are highway. I've been changing anywhere between 5-7K, generally speaking.

[Secret Chimp]

If you do mostly highway driving, your owner's manual probably has you under the normal cycle (vs. severe or however it's termed).
The manual for my 12 year old car has oil changes every 5,000 miles for the normal condition cycle, and that's presumed to be with dino oil. Take a look at your manual's service intervals and you're probably falling safely within what they recommend.

[TurboDan]

Oh yeah, and I read the Oil FAQ thread. Just trolling for opinions...

[93JC]

Change your oil when it's due to be changed: look in your owner's manual and follow the recommended schedule.

[GoCougs]

Problem is you don't know until you test the boundaries beyond the automaker's recommended interval, and that can only be done (safely) with an engine oil analysis. Google the topic and you'll find a number of places that will do that for you for pretty cheap.

Oil change interval with synthetic oil can be substantial; the 911 for example has a 15,000 mile interval. However, I have to think that the engine was designed for it to some extent. Personally I'd not use synthetic unless it came from the factory that way; in this you know the automaker put millions $$$ into the certification of the interval (like the 911).

FWIW, my Accord manual explicitly says to not exceed the recommended interval even using synthetic; not much of a problem IMO considering the intervals are already quite lengthy using dino oil; either 7,500 miles (V6) or 10,000 miles (I4).

[CJ]

Our service interval is whenever the Maintenance Minder goes down to 15%.

[S204STi]

Change your oil when it's due to be changed: look in your owner's manual and follow the recommended schedule.

Correct answer.

/thread

There is a reason OEMs don't bother certifying their engines for synthetics; it's because there is no discernible difference in longevity.  What really causes the need to replace the oil is the break-down of the additive package which is fairly standardized across the industry.  Some oils advertise themselves as being "Long Life" oils but until OEMs certify that they do in fact last longer I'll just change it at the recommended mileage as usual.

[SVT_Power]

I change mine every 7,000 kms which is just under 4,300 miles. I know this is almost the minimum for synthetic but I spend a lot of time in the top half of the RPM range, and a while near redline as well. But lately most of my driving has been highway (but cruising at close to 4k) so I thought about going longer between changes but i've just been sticking to it.

[VTEC_Inside]

Factory intervals here... Accord(every 6000kms) just gets dino oil, but RSX (every 8000kms) gets synthetic.

If you are really interested, google "Blackstone labs" and send them a sample of your oil for analysis. Then you'll have a more quantitative way to decide.

[Byteme]

Correct answer.

/thread

There is a reason OEMs don't bother certifying their engines for synthetics; it's because there is no discernible difference in longevity.  What really causes the need to replace the oil is the break-down of the additive package which is fairly standardized across the industry.  Some oils advertise themselves as being "Long Life" oils but until OEMs certify that they do in fact last longer I'll just change it at the recommended mileage as usual.

Ditto, Ditto, Ditto.  Synthetics are a waste of money IMHO.

I've never used pure synthetics like Mobile 1, but I've used the blends like Motorcraft simply becasue they wer eno more expensive than the non-blend at the time.  Still changed the oil every 5,000 miles.  Oil and filters are pretty cheap.

On synthetics, the reason I've not used them is oil needs to be changed for a couple of reasons, contamination and the additive package ending it's useful life.  I 'm not sure that using a synthetic would do anything to alter the contamination issue.  The oil will still pick up blow by and combustion products and the bits of the engine that wind up in the oil from normal usage.  In fact you want it suspeded in the oil and trapped by the filter, not settleing where you don't want the crud to settle.

[S204STi]

Exactly right.

Also, quick note on Motorcraft:  Ford rocks for providing OEM parts and chemicals off the shelf at a highly competitive price.

[Raza]

5000 to 7500 should be safe in your car.  I always got mine done at 5000, as I do now. 

[SVT_Power]

Exactly right.

Also, quick note on Motorcraft:  Ford rocks for providing OEM parts and chemicals off the shelf at a highly competitive price.

Except for their tranny fluid. Ridiculous price, but almost magical.

[TurboDan]

Synthetics are a waste of money IMHO.

In 1.8T Passats, dino oil = engine sludge (and voided warranty!). Proven.

[S204STi]

In 1.8T Passats, dino oil = engine sludge (and voided warranty!). Proven.

FWIW Subaru doesn't require synthetics for my car, but they do mandate a 3750mi interval for turbo cars.

The basic point here though is to read what your owner's manual says about the matter and stick with that.