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In the mid to late 80s, the water-cooled transaxle Porsches (928, 944, 924, 968) had an oil change interval of 15,000 miles, recommended by the manufacturer. I know the 951 (turbo) had 7,500 intervals instead of 15K.
I have read many threads about what people do. Many of us owners of the above listed models in the 2020's don't drive ours 15,000 in a year as we cherish our 40 year old P-cars. So a lot of people change oil 6 months or 12 months, regardless of miles. I am Not including the daily driver cars or race cars in this, as they would certainly have a different maintenance schedule based on how they use the car.
My curiosity is about three things:
1) Do we change our oil too frequently as car owners in general? People argue 3m/3K pretty on the regular and there is definitely an opposing camp (in regards to ALL cars, not just P-Cars) I got my drivers license in 1986 and I learned to wrench on my 1st car a 1975 Beetle, and in 1988 my second car was a 1979 924 and I Really learned to wrench since I couldn't afford to take my car to a mechanic. Getting to a point ... I remember back in the late 80s, mechanics were preaching 3,000/3 month oil change intervals for ALL cars, everywhere! (I live in the US, Texas)
2) I am more interested in this question though: Were 15,000-mile oil change intervals really that "safe" for the cars when these 1980's transaxle cars were brand new? I mean, Porsche was recommending 15K, so they must have has some confidence in oil lasting that long?
3) Do you think Porsche dealer mechanics (in the 80s) recommended 15K intervals to new owners? Or were they saying, "Yeah, Porsche says 15,000 but I wouldn't trust that, I'd change it sooner."
Feel free to offer opinions on any of my questions. I know some of you may have had a brand new transaxle car from the 1980's and could offer first hand answers!
Last edited by Chalt; 01-10-2023 at 04:46 PM.
Reason: Added a question
In the mid to late 80s, the water-cooled transaxle Porsches (928, 944, 924, 968) had an oil change interval of 15,000 miles, recommended by the manufacturer. I know the 951 (turbo) had 7,500 intervals instead of 15K.
I have read many threads about what people do. Many of us owners of the above listed models in the 2020's don't drive ours 15,000 in a year as we cherish our 40 year old P-cars. So a lot of people change oil 6 months or 12 months, regardless of miles. I am Not including the daily driver cars or race cars in this, as they would certainly have a different maintenance schedule based on how they use the car.
My curiosity is about three things:
1) Do we change our oil too frequently as car owners in general? People argue 3m/3K pretty on the regular and there is definitely an opposing camp (in regards to ALL cars, not just P-Cars) I got my drivers license in 1986 and I learned to wrench on my 1st car a 1975 Beetle, and in 1988 my second car was a 924 and I Really learned to wrench since I couldn't afford to take my car to a mechanic. Getting to a point ... I remember back in the late 80s, mechanics were preaching 3,000/3 month oil change intervals for ALL cars, everywhere! (I live in the US, Texas)
Yes. However, on a VW bug, without an oil filter, 3,000 miles worked well.
2) I am more interested in this question though: Were 15,000-mile oil change intervals really that "safe" for the cars when these 1980's transaxle cars were brand new? I mean, Porsche was recommending 15K, so they must have has some confidence in oil lasting that long?
15,000 miles is a long time. I recommend my clients change the oil every 7500 miles. If they don't drive their cars very much/far, I suggest changing the oil when the oil filler cap has "milkshake" oil/water on it.
3) Do you think Porsche dealer mechanics recommended 15K intervals to new owners? Or were they saying, "Yeah, Porsche says 15,000 but I wouldn't trust that, I'd change it sooner."
No idea....although my experience with the dealer mechanics, back when 928's were new, is that they dreaded getting in a 928....for anything.
Feel free to offer opinions on any of my questions. I know some of you may have had a brand new transaxle car from the 1980's and could offer first hand answers!
my experience with the dealer mechanics, back when 928's were new, is that they dreaded getting in a 928....for anything.
How do you think a present-day Porsche dealer technician feels about getting a 928 in their bay in 2023? Any better than 35 years ago? (I am smiling as I type this, and I chuckled at your comment)
I personally do it every year as the detergents in the oil degrade. This is with standard dino oil.
Otherwise I change it every 10k as the sump in the 928 is so large. It takes over 8 quarts every time I do it.
But yeah, the dealers hate working on them. Even my local dealer that still works on them regularly doesn't like them because they can never beat book time lol.
How do you think a present-day Porsche dealer technician feels about getting a 928 in their bay in 2023? Any better than 35 years ago? (I am smiling as I type this, and I chuckled at your comment)
Unless they are a "Classic Dealer", I doubt that they would even accept the car.
I change oil all 10.000 km. 100 € for oil and filter is not much and the engine is very clean inside with the Esther technology. I have a lift and a 1000 l barrel for used oil, why get the risk of wear in the engine.
My cars must work hard on Autobahn.
I change the oil about every 7500-10000 depending on if I am taking long trips or just summer drives. More often for summer drive, less often for long 2000 mile trips.
No one that does used oil analysis on their oil changes would run or should run even today's oils past 5,000 miles. By then the Viscosity indices have dropped so the 15/50 or 20/50 you put in has become 10/40 of 5/30 and the oil has become more acidic than basic, and acidic oil eats metal. It should be changed at least once a year or every 5,000 miles.
Here's a perfect example from one of my 997s where I missed the normal interval (wife's car and she forgot to mention it to me). Look how the metal ppm jumped up, flashpoint declined, the acidity increased (TAN vs TBN), and the viscosity decreased.
Changed brands for the 4-19-17 change and you can also see how much better the oil I changed to maintains it's Viscosity, even at more miles.
No one that does used oil analysis on their oil changes would run or should run even today's oils past 5,000 miles. By then the Viscosity indices have dropped so the 15/50 or 20/50 you put in has become 10/40 of 5/30 and the oil has become more acidic than basic, and acidic oil eats metal. It should be changed at least once a year or every 5,000 miles.
Here's a perfect example from one of my 997s where I missed the normal interval (wife's car and she forgot to mention it to me). Look how the metal ppm jumped up, flashpoint declined, the acidity increased (TAN vs TBN), and the viscosity decreased.
Changed brands for the 4-19-17 change and you can also see how much better the oil I changed to maintains it's Viscosity, even at more miles.
I don't see much difference between those samples.
Explain, for us that don't have oil analysis done?
01-10-2023, 04:01 PM
Oil change interval - 1980s vs the present
