SD Porsche Fan

Had been running Castrol 20-50. The car weeps oil from the crank seal. I get about 2 drops on the garage floor after driving. I read a few posts where some were running Valvoline high mileage. I am a little worried about the "synthetic blend" since the car had seen only dino oil it's entire life.

I have only driven the car 1500 miles since my last oil change over a year ago. The oil still looked nearly new. I just figured it needs changed at least once a year regardless of mileage.

Any thoughts on hight mileage products, synthetic blends or changing the oil based on time as opposed to miles?

sawood12

I tend to stick to Porsche recommendation of 6kmiles or 6 months - moreso the 6k miles than 6 months though. I tend to think the oil has been under the earth for millions of years under conditions worse than in my engine so what difference is a couple of months in my sump going to make? I think the latest generation of fully synth oils mean that they perform better for longer.

Not sure I believe the marketing line on oils for high milage engines. How is one 40 grade oil more suited to high milage engines than any other 40 grade oil. The viscosity of a 40 mineral oil is exactly the same as a 40 fully synth or a 40 semi-synth. I say just go for the best quality fully synth at a grade that makes you feel comfortable. I personally use Silkolene Pro S 5w40 and have had no probs at all.

VWaddict

In Europe many manufacturers recommend annual oil changes, regardless of mileage.

The theory is that there's a slow chemical deterioration from combustion by-productes being introduced into the oil, as I understand it. -I was told that the acdity of the oil can change over time slowly.

The way I see it, you should be able to drain and refill without necessitating a filter change, although draining the filter is also a good plan...

Myself, I have LONG since stopped trying to save money on oils or oil changes: once a motor is broken in, if in doubt change it has always been my motto... -So I've changed the oil once ot rwice too frequently... I've still got a factory-smooth running motor, with almost a quarter of a million miles on it.

Keith

Spidey944

Just a quick leason from my days at Valvoline. IIRC the molecules on a full synthetic oil are all the same size. A semi-syn most are same size. And a conventional oil, you have long chain, short chain, and medium size molecules. That is why a conventional oil will leak less than a full synthetic, and a full synthetic will leak the most. Same is true if you have oil blow-by, or bad rings. The engine will consume it faster. The trick is finding a suitable oil weight, and type, that works best for your vehicle.

I once used 10w30 full syn in my 347 Stoker Mustang, and it burnt 2-3 quarts in two weeks. I switched back to a 20w50 conventional like I had been running, and it went back to normal oil usage. Just my opinion. I'm sure there are varying theory/facts regarding the usage and construction of synthetic oils that could be debated all day long.

Diver944

I also stick to the recommended 6k miles or 6 months whichever comes first. It doesn't matter how good your oil is, it's the contaminants and moisture (ie water) that gradually get in there that will ultimately cause problems. Water on your bearings is not good for long life.

An oil change costs less than half a tank of gas. How much does a rebuilt engine cost?

SD Porsche Fan

From reading on the Valvoline web site their "high mileage" oils are said to condition seals/gaskets to stop leaks. The fact that my car is nearly 19 years old is a big reason why I haven't switched to synthetic for the fear of making the crank seal drip worse.

I was going to change the oil this spring (6 months) but haven't driven it hardly at all. My goal for next year is to drive it more!

MichelleJD

I run that same oil in my Bimmer and have had no issues.

dime1622

From my years of reading posts on the board, I personally wouldn't switch to a synthetic. I've heard enough stories of people making the switch and the leaks getting worse.

LFA951

I have an oil leak too and I was using Amsoil 20W50, but at $10 a quart I was pissing away money weekly and I tried the Valvoline high mileage, but found out that the VR1 Racing oil is better for our cars cause it has better protection, so I am using it now and happy with it, no need for synthetic blend, just get regular natural dino oil.

RKD in OKC

My old hot rod race car mechanic dude recommends Pennzoil Longlife 15w40. Says it is Pennzoils GT Racing oil designed for Turbo race cars. He also recommends changing oil every 3000 miles due to turbo temps and water absorbtion. Says any other oil is just a matter of how much money you are comfortable pouring out the dran hole.

sawood12

Modern synthetic oils should be good for more than 3kmiles for normal road use with the odd track day. Modern cars like the new 997's for example have an oil replacement schedule of around 20k miles. Yes they are more modern engines but they use Mobil 1 which is not an especially 'special' oil. I'm not suggesting that a 20k service interval for our 951's is a good idea but a 6k mile service interval should be perfectly adequate assuming normal road driving. It stands to reason with frequent track usage then more frequent changes will be needed.

Modern synthetic oils are much more resistant to breakdown from products of combustion, contamination of other petrochemicals and heat from turbo's - they are a different league from the oils that were around when our cars rolled off the production line 20yrs ago.

Droops83

Yes both Porsche and BMW cite 15k intervals for oil changes on their newer cars---and that is insane! The Mobil 1 0W-40 that they both require is some of the best oil made, and it's true it will physically last 15k miles and protect for that long, but the 15k mile interval is more of a marketing campaign than a good idea. They don't take into account sludge buildup, which can be a big problem w/ the newer Variocam/VANOS type engines with tiny orifices for those systems you do not want clogging up!. Also let's face it many people don't drive these cars like they should and do lots of cold starts/short trips which builds up a lot of moisture in the oil which eventually forms acids. I would not want that in there for 15k miles. If you read the fine print, both Porsche and BMW still recommend that you change the oil annually regardless of mileage, due to breakdown of additives as cited above (but BMW dealers will refuse to change your oil on the newer cars any more often since they can't reset the service light to reflect that, even if you offer to pay them! Most of our customers who have newer cars under warranty pay us to do the oil changes at 7500 miles). At my shop we recommend 7500 mile intervals or 1 year for cars running synthetic and 6 months/5,000 miles for older cars running dino oil (we use Castrol GTX 20W-50 for most older Porsches and BMWs with great results).

Do a user search for a very smart guy named Doug Hilary. He was in the petroleum engineering industry for years and has published many oil-longevity studies with his 928, with oil analysis reports and everything. He found in all cases that really good oil would protect very well for a 15k mile+ range, but even he STILL recommends changing it annually.

We have some 944/951 customers who insist on Mobil 1 15w-50, which is fine since in those cases the engines have been running on synthetic for awhile now and they are the types of customers who would fix any oil leaks right away anyway. On my 90k mile 951 I just bought last month, I still run GTX 20W-50 because that's what we always put in it (we have worked on it for the original owner since new!) and it works fine. That high-mileage stuff is mostly BS, you can learn a lot about a motor oil by reading the back of the bottle carefully and reading which standards it has passed (API is mostly BS, look for ACEA ratings on newer synthetics).

RKD in OKC

On miles...
Audi (turbo) used to offer free oil changes for the warranty period of the car at intervals of 15,000 with synthetic. They quit because the motors were cratering (heard this from a reliable service tech). They now recommend 7,500 miles and don't do it for free any more.

My 2007 BMW (non-turbo) has free oil changes at 15,000 intervals and I would change it twice as often if I planned to keep the car for longer than 3 years.

On recommendations for current models...
Your 18-20 year old car does NOT have the specs, clearances, cooling, oil passage design, or technology of the current models. Just think of leaded gasoline. Was an additive put back in to replace lead or were new motors designed and changed to work without lead? So why is it again that you would follow recommendations made for a newer motor?

The state of motor oil...
I personally have not heard of any major breakthrough changes in motor oil in the last 10 years. The changes have been in the newer motors not the oil. Every time I see an ad for some newly formulated motor oil I can't help but think what additive did the EPA make them remove for some emissions reason, And how long, if ever, will it actually take the motor oil companies to find anything that works nearly as well as the additive that was removed. Mobile 1 used to be the best oil you could get, now it does not measure up to what it used to be.

I can change my cheap dino oil every 3000 miles and spend about the same as a good full synthetic at 15,000 miles!

2¢

Droops83

RKD you are pretty much right on . . . though I hope you didn't think I was recommending long oil change intervals for 944s? For those, 5,000 mile intervals are fine, 3,000 doesn't hurt, but any more often than that is not really worth it. In fact if you change your oil too often (say every 1,000 miles) you can kill your cat since the additives in the oil that burn off can coat it, though this applies more to OBD2 cars, and I guess not many of you guys on here run cats anyway!)

There have been pretty good advances in motor oil recently, but only in certain cases. For example, not all Mobil 1 oil is created equal. Mobil 1 0W-40 is some of the best stuff out there, it meets all of the latest and most stringent standards set by Porsche, BMW, MB, Audi and the like. Mobil 1 5W-30, on the other hand, is complete crap. The oil companies get away with whatever they can to make a buck, and they use cheaper base stocks in certain weights. Look for ACEA ratings on the back of oil bottles. Those represent European standards for oil quality, and the ACEA is controlled by car manufacturers, and of course it is in their best interest that their engines are protected. American API ratings are set by the oil companies themselves, and it is in their best interest to make money, not to protect engines.

Mobil 15W-50 is pretty good, good enough for 964 and 993 911s, and early Boxsters/996s used it, and like I said before we use it in some 951s with no problems. But I must state that even with how good it is for modern cars, do not use Mobil 1 0W-40 in any kind of 944! Though it is thicker than the 0W would make you think, it would leak like a sieve! Stick to 15W-50 or 20W-50 in any 944 based car.

Fluidplay

There was a great post on this subject a while back regarding updated oil additives (paticularly to Mobil 1)and what it's potentially doing to our motors. There were several recommended brands listed. Try a search, it was a really informitive read on todays motor oils.