switching to synthetic at 100K

I just switched at 76K

What kind of "synthetic"? I generally accept "synthetic" to be more of a buzzword once Castrol NA let their marketing dept loose in the late 90s. I consider most "flavors" of Castrol Syntec sold in the US to be somewhere between current high performance "synthetic" oils and current "conventional" oils. There are others marketing "Group III" base oils as synthetic, which I consider marketing gone awry.

As long as you've taken good care of your engine, I wouldn't worry about leaks.

I personally use Mobil 1 5W-30 in my 2004 WRX.

Not many years ago, I was told to beware switching between regular and synthetic oils because, if you switched to synthetic you couldn't switch back to regular ever again. I was told that the oils didn't "mix" and would ruin my engine. What a load of nonsense. But the above illustrates the point that there is a lot of misinformation out there on synthetic oils. There is no evidence that synthetic oil provides any better protection than conventional oil. It does provide a good deal of piece-of-mind, though. That could be more important than the extra $$ saved continuing to use conventional oil. josh

I think modern engines with modern oils in them can be quite reliable and experience much greater longevity than in the past. That said, 'synthetic' oils have an edge on 'non-syn' oils in lab tests and oil analysis in most cases - does it mean you'll get twice the sevice from an engine? or 2% more? I dunno. I have the means to afford synthetic and run it in both cars 5-30 in the Outback H6 and 5-40 (Rotella) in the WRX.

Carl

Hi,

There's so much myth about synthetics out there one doesn't know what to believe. People can't even agree on what IS or ISN'T a TRUE synthetic. I won't get into that one.

From personal experience, if your engine's not burning oil, and has no noticeable leaks, the switch will probably go well. IF it's burning oil, I seriously doubt you'll see an improvement--you'll just be burning more expensive oil now.

On the leak thing: it's been reported over the years synthetics CAUSE leaks. Don't think so myself, at least not with today's versions (there WERE some documented problems at first.) They DO a better job of cleaning, and CAN dissolve some of the old crud that may be preventing a leak, though. This varies by engine. Many changes have been made over the years, both in the oils and seal chemistries to ensure leaks aren't being caused.

Lots of people report huge gains in fuel economy. Don't think so myself, based on very extensive fuel records over several cars w/ synthetic and dino oils. For myself, a gain of no more than about 2% over 10s of 1000s of miles is all I've seen.

Benefits: if you live in a hot climate (I do), you'll get better protection and less breakdown of your oil over a given time. This CAN allow longer change intervals, as long as you're NOT under warranty (so you're safe!) If you're under warranty, you've gotta change as the book says regardless of the oil you use.

You may enjoy greater peace of mind, knowing you've done your part to help your engine. To some, this is very important. To others, it's not. Oil is one of those "my brand's the only brand" things people love to argue about and my Mobil 1 buddy can argue until he's blue in the face, but he won't convince my Castrol GTX neighbor there's any reason to change!

So try the switch. If you don't notice improvements, yes, you CAN go back to dino oil and nobody's gonna be the wiser.

Rick

One quick observation - do not be concerned at how incredibly dark the syn-oil will be when you change it, particularly on a vehicle switched from 'dino' oil. Syn keeps 'varnish' in soulution/suspension and it's dark because that is the stuff that otherwise would be coating the engines internal parts.

Carl

My understanding is that syn oil is great, but if you have any oil leaks the syn is so good at getting into ever nook and cranny it can make your oil leaks worse. Otherwise, it just takes a lot more abuse than petroleum based oils. If you forget an oil change or your car overheats a bit you don't have to freak out with synthetic.

Switching to Syn-oil is best done right after break-in, around 15-20K. If you change it at 3-4K mile intervals after that ( with a filter), your engine will last forever...... At the time you change to it, it almost puts engine wear into suspended animation...

Is it that Rotella T Synthetic 5W-40 for diesel engines? Asking seroisuly since use it for my Yamaha FZ-1 (12K RPM read line) and think of using it for my Outback too.