synthetic oil...

[pearldrum]

Okay, I just switched to Mobil 1 and was wondering how often I should change the oil and the filter? I had heard that Synthetic can last past 20k, but obviously it would be really dirty. How long do you all run synthetic and how long do you keep the same filter?

[divezic]

I change the Mobil1 every 6000-7000 miles or once a year, whichever comes first. I change the filter every 6000-7000 miles or 6 months, whichever comes first. Not something from an official Porsche document but it sounds logical...to me.

[Wolf1]

I run Mobil 1 in all of my vehicles. I change it every 4-5k including filter. However I dont use it to stretch out the change intervals. My primary reason for synthetic is the added protection.

[flangermog]

I've been warned several times about using synthetic oils such as Mobil and Magnatec etc. in older cars.

Apparently, although they will protect more in a newer engine, the oil is too thin for an older engine which has worn a little (which all of them do). A thicker, more gloopy oil will provide more protection when the engine is up to temperature and running.

Using a synthetic oil means you are more likely to start burning oil in an old car as it can sneak through the tiny gaps that have worn away through the passing of time. This, of course means the oil is no longer performing its function as effectively.

My car had synthetic oil in when i bought it and i used to get a lovely plume of dirty smoke out the back (as well as soot around the tailpipe).

I changed to a thicker grade oil and now the car ticks over more smoothly and doesn't burn any oil.

I beleive it is great stuff if used on the car from new as the level of protection is higher, but in an old car (as all 944s are now), unless synthetic oil has been used from day one, there is little benefit in spending the extra cash.

[cpm01nws]

I've used Mobil 1 in all my vehicles for many years and highly recommend it. Porsche recommends it. The primary reason you might be cautioned for older vehicles is if they tend to leak oil. Synthetic will leak more. At the price $4-$5 a quart, leaks get expensive.

Change Regulary!
Even though it is synthetic and doesn't "wear out", it should be changed regularly as it picks up contaminents as any oil will. These contaminents are the primary reason any oil needs to be changed. Some aircraft maintenance facilities clean/filter the synthetic oil to remove contaminents and reuse it. I change mine every 6,000-7500 miles.

[Mark_944S2]

Yes the porsche maintenance interval on the S2 is 15K (Boxster is the same) with synthetic oil. If you are worried about particulates in the oil you could change the filter at say 7.5K. Synthetic will last to 50K with no change in viscosity but particulates will be a problem by then!

There is no reason synthetic oil should burn more IF its the same viscosity. My 115K S2 runs great on 15/W50 Mobil 1, no leaks, no burning. Obviously if you put 0/W30 in an old engine it'll probably burn.

if you change synthetic every 4-5K can I suggest it would be easier to just flush the money down the toilet and that'll extend your engine life just as much. To the guy on the 350Z board who changes Mobil1 every 1.5K, keep it up - Mobil must love you.

(Owner of 115K S2, always run on synthetic, changed every 15K, no engine wear detectable - compression is 200/195/200/195).

Mark

[sasquatch]

1987 944na, 178,xxx miles, Mobil 1 15/50, Mobil 1 filter. Change once a year, every September. Averages out to 9k miles. Oil analysis shows that the oil is still clean and should be reused. I just can not let it go further. Car is autocrossed and driven like a madman.

Jay

[Wolf1]

Originally posted by Mark_944S2

if you change synthetic every 4-5K can I suggest it would be easier to just flush the money down the toilet and that'll extend your engine life just as much.

Sure you can suggest it, but I will just ignore you..
Oil is cheap, engines are not...

[Blackfoot]

use mobil-1 in the bmw, change it every 10k or so, filter every 5k.

_____________
-too many cars

[Britwrench]

I really wonder if there have ever been any scientific tests that prove (or disprove) that changing oil every 3000 - 5000 actually extend engine life.
We pull different engines apart and I've smelt the burnt old oil in several engines, still they all seemed to do plenty of miles though.....

My last VW did about 130,000 miles on probably 5 oil changes, was still running well and had normal oil consumption. Obviously, if you want to keep the car regular oil changes are a good idea, and twice a year seems to work out well.

[sasquatch]

Originally posted by Britwrench
I really wonder if there have ever been any scientific tests that prove (or disprove) that changing oil every 3000 - 5000 actually extend engine life.

I don't know how scientific this is, but I have been really interested in this for many years. We have an account with an oil lab through work, so it is easy for me to get oil samples analized. I have performed many samples on oil in many of my vehicles. Some of the more noteworthy samples:

1991 Yamaha FZR 1000. Mobil 1 15/50 after 2100 miles including 4 open track days where 2-300 miles were put on with the tack buried between 9,000 and 12,500 rpm's. Analysis showed no noticeable breakdown of the oil since new. No adverse levels of contaminants either.

1976 Executive motorhome, Dodge 440-3 motor (built to the nuts) 3,600 mile road trip, Chevron Delo 400 15/40, oil in excellent shape, told to continue use. I think the actual statement was "All oil paramaters within acceptable ranges, sample at next normal interval"

1998 Monaco Executive motorhome. Cummins M-11 450hp turbo diesel pusher (1650 ft/lbs of torque for you torque junkies). Delo 400 15/40, 37,650 miles on oil change (yeah, it was a busy year and we just plain forgot it). Analysis was good. Showed some elevated levels of ash, but still told to run it untill next normal cycle.

1987 Porsche 944na, the farthest I have gone is 12k on Mobil 1 and you guessed it, the analysis was excellent.

So, from this totally unscientific test, we change our oils too darn often. What people fail to look at is that the 3k mile intervals were created many moons ago when things were very different. Engines were not created with the same tight tolerances as today, and they were all carburated with little to no concern for how well they were jetted. All the blow by into the crankcase would contaminate and break down the oils.

Engines also run much hotter today. This is actually a good thing for oil as it burns off acidic deposits left by the cumbusion process. The motors are also running so clean that there is not much contaminants to begin with.

I think we can saftely go 10k on dino oil (5k on filter) and 20k on synthetic (5k on filter). But that is my opinion.

Jay

[Dark Skies]

Regarding scientific testing of oils. Back in the early nineties I was subcontracted to the Esso (Exxon) Research Centre as a test driver.

Basically testing involved purchasing a broad cross section of family and performance cars from new, stripping down their engines, measuring all the tolerances and then rebuilding them for driving on the public highway.

The cars would then be driven virtually nonstop (in shifts) over all manner of driving terrain (country, town, city and motorway) for some 250,000 miles (oil samples taken every 10,000 miles) pror to stripping down the engines to see what wear had occured. I spent about seven years involved in this sort of testing so I became quite authorative on oil degradation, ash build up etc. etc.

One of the oils they tested was Mobil 1 against a whole range of similar lubricants. As it turned out this oil came out tops in pretty much all the trials. Armed with this inside information I thought that it'd be worth giving it a shot to see how it worked in my trusty old 250,000 mile 944. The results were suprisingly disappointing - the car drank oil like a barfly at happy hour and the exhaust started to smoke slightly.

I changed back to good old affordable Castrol GTX and the car settled back to a clean exhaust and the occasional gentle tipple after evensong by way of oil consuption. Me and her we don't much care for change.

The reason is, of course, obvious - back in the early eighties Castrol GTX was the top kiddy on the block and Porsche engine tolerances were designed with this type of oil in mind. Porker engines will happily do a good 300,000 miles if properly looked after - mine's done 350,000 and still doesn't smoke. Granted the engine has probably a good bit of wear but using a "gloopy" oil as one poster says packs out the worn areas and protects the moving parts as Porsche intend. If you swap this for a thinner oil it doesn't manage to fill out the worn areas or lubricate as effectively.

So if you have a brand new engine use a top spec oil like Mobil and you'll be fine. On a worn engine - especially an older one designed with larger tolerances you should stick with a quality oil of the recommended viscosity of the type the engineer designed his motor around.

Changing oil every 3,000 miles or so is a waste of money - regardless of whether it's a synthetic or mineral or semi-sythetic. Modern oils from recognized brands can easily do 20,000 miles without significant deterioration. Changing at the recommended 10,000 (or whatever it is) mile interval with a new filter will be more than sufficient outside of track use.

Yes you could opt to stretch out to 20,000 mile changes but I wouldn't recommend that - it's a good idea to keep an eye out for early signs of trouble (water, metal filings, bits of sealant, gasket, chipped teeth and other unusual stuff ) floating around in the oil. At around the 100,000 mile mark I found a tiny bit of metal that looked like the corner off a gear tooth or something. I have no idea what it came off but I was sure it wouldn't be good to have it floating around in the oil for another 10,000 miles. Numerous oil changes and 250,000 miles later I reckon I was probably right.

[Mark_944S2]

Funny how its the oil companies advising us to change the oil every 3K, while Porsche say every 15K. Who would you trust?

Mark

[brett25]

i am interested in this topic too. i was looking at an article on the web which said that in Europe, the intervals between oil changes are much longer than in the US.-like 15,000 miles. The article also said that, while the oils are manufactured for these intervals, the companies do not advertise this information in the US markets. So basically,in the US, we are changing oil too frequently ( and wastefully)) and that most oil brands (non-synths) do last much longer than the 3-5,000 miles recommended intervals. Synthetics of course, will last even longer.

[Mark_944S2]

brett25,

Having lived in the UK, and now living in the US, I think you are absolutely correct.

For an example a Nissan 350Z has 7500 mile intervals in europe and 3750 over here. Why? The engines the same, and so's the oil.

I know an engineer at Mobil just for a laugh tried running his car on Mobil 1 indefinitely, just testing a sample of the oil every 10K. At 60K there was no sign of degredation of the oils properties although it was very black and acidic by then.