mixing oil weights
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Joined: Jul 2010
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From: San Francisco, CA
mixing oil weights
Hi all,
Proud owner of an 89 964. I recently had an oil change done at the local dealer, who replaced my oil with 0W-40 non-synthetic. Given the nature of the car, I generally have to top off a quart or two of oil once per month, but was surprised that I couldn't find 0W-40 non-synthetic at any local auto parts store. In fact, one guy working the register told me the car isn't even supposed to run on that. I checked the manual and the preferred seems to be 15W-40.
Is it safe to mix 0W-40 and 15W-40? Is it "bad" I'm running 0W-40 in the first place?
Proud owner of an 89 964. I recently had an oil change done at the local dealer, who replaced my oil with 0W-40 non-synthetic. Given the nature of the car, I generally have to top off a quart or two of oil once per month, but was surprised that I couldn't find 0W-40 non-synthetic at any local auto parts store. In fact, one guy working the register told me the car isn't even supposed to run on that. I checked the manual and the preferred seems to be 15W-40.
Is it safe to mix 0W-40 and 15W-40? Is it "bad" I'm running 0W-40 in the first place?
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From: San Francisco, CA
Yes, when I bought the car I was told it's the nature of air cooled motors, coupled with the fact this particular car needs a case-through bolt reseal (something I was also told needs to be done on all old Porsches to prevent oil seepage).
Three Wheelin'
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From: on the waterfront, Kobe, Japan
i ran 20w50 in my 964 (pennzoil) with virtually no need for top ups between oil changes.....
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I'm not sure of the full details. Everyone I've spoken to, including on this forum, has told me that air cooled motors leak some oil over time. In any case, the oil gauge runs in the middle for a few weeks, then stays at empty until I top it off at the end of the month and that's just always been the way of the land for me.
Burning Brakes
Joined: Nov 2006
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From: Wilmington, NC USA
Mine leaks oil to let me know there is still some in it. Once I do not see oil leaks, I know I am in trouble. 
Wish I could answer your above question. I have heard of people mixing the same brand of oil that has different weights, however it sounds like you do not know the brand. I would not think you would want to mix synthetic with non-synthetic. (I am definitely no expert though.)
Good luck.
Wish I could answer your above question. I have heard of people mixing the same brand of oil that has different weights, however it sounds like you do not know the brand. I would not think you would want to mix synthetic with non-synthetic. (I am definitely no expert though.)
Good luck.
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From: UK
Hi all,
Proud owner of an 89 964. I recently had an oil change done at the local dealer, who replaced my oil with 0W-40 non-synthetic. Given the nature of the car, I generally have to top off a quart or two of oil once per month, but was surprised that I couldn't find 0W-40 non-synthetic at any local auto parts store. In fact, one guy working the register told me the car isn't even supposed to run on that. I checked the manual and the preferred seems to be 15W-40.
Is it safe to mix 0W-40 and 15W-40? Is it "bad" I'm running 0W-40 in the first place?
Proud owner of an 89 964. I recently had an oil change done at the local dealer, who replaced my oil with 0W-40 non-synthetic. Given the nature of the car, I generally have to top off a quart or two of oil once per month, but was surprised that I couldn't find 0W-40 non-synthetic at any local auto parts store. In fact, one guy working the register told me the car isn't even supposed to run on that. I checked the manual and the preferred seems to be 15W-40.
Is it safe to mix 0W-40 and 15W-40? Is it "bad" I'm running 0W-40 in the first place?
Is it safe to mix 0W-40 and 15W-40? Yes
Is it safe to mix synthetic and non synthetic? Yes
Is it "bad" I'm running 0W-40 in the first place? No.
But it might be a bit thin if you engine is heavily worn, although i am not an advocate of curing oil leaks with thicker oil i always put in what the manufacturer spec says.
I would just be more concerned that you aren't sure of what oil was used, but when you say local dealer is that Porsche Dealer? This would give more insight to the oil used.
One last question, if its just a general car garage, what makes you think the garage put 0w40? or non synthetic or 15w40 or any spec? was it simply because they said they did?
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From: Vancouver Island, BC , Canada
In any case, the oil gauge runs in the middle for a few weeks, then stays at empty until I top it off at the end of the month and that's just always been the way of the land for me.
Just checking; are you saying that the oil gauge is showing half full when running and the engine at operating temp.? If so, you are overfilled. The oil level gauge should only indicate at idle on level ground and at operating temp.
What does your dipstick show????
Just checking; are you saying that the oil gauge is showing half full when running and the engine at operating temp.? If so, you are overfilled. The oil level gauge should only indicate at idle on level ground and at operating temp.
What does your dipstick show????
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From: San Francisco, CA
That's right, after the engine warms up (about 3/8ths of the way off the bottom), the oil gauge shows half-full. This happens for a few weeks until it drops lower and lower and eventually doesn't even move. I was told never to use the dipstick because it's horridly inaccurate by the inspecting mechanic when I bought the car.
Three Wheelin'
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From: Seattle xburb - I can't see the Emerald City, but I know it's out there somewhere
Wow... in any engine, the dipstick (when read correctly) is the judge.
In these cars, when you learn the nuances of the gauge, it can be used as a good reference. But use only the gauge? Not me, my friend.
How long have you had the car? How many miles have you put on it? Obviously enough to gauge consumption... How many miles is "a quart or two a month" for you?
These engines can consume what I consider to be a fair amount of oil, and still be considered healthy. But they vary a LOT. Mine uses less than a qt. in a 4000-mi. change cycle. But here are my thoughts, FWIW: these oil-cooled motors are pretty hard on their lubricant, and you won't see many here using the 0W-40 weight, even though Porsche says you can. "Can" does not equal "should", and this is an area where Porsche treats its old air-cooled's like bastard stepchildren in terms of recommendations. I've never even heard of a 0W-40 dino oil, and I can't even find mention of it anywhere on the interwebz. Doesn't mean it doesn't exist, but why would he use about the most undesirable oil I can think of in there? I also personally wouldn't mix dino and synth - maybe to get you home, but I just wouldn't do it voluntarily, and i would change it as soon as I could.
I personally use a really good 10W-40 synth., some folks use Brad-Penn dino, some folks use Mobil 1, and then there's a myriad of other brands. These engine have special requirements that make otherwise very good oils not appropriate. They have "special needs" in chemical compostion, particularly in zinc & phosphorus to protect the cam & valve train. Take a little time, do a search (there's more info on here on oil than you could ever imagine
), and then decide.
In these cars, when you learn the nuances of the gauge, it can be used as a good reference. But use only the gauge? Not me, my friend.
How long have you had the car? How many miles have you put on it? Obviously enough to gauge consumption... How many miles is "a quart or two a month" for you?
These engines can consume what I consider to be a fair amount of oil, and still be considered healthy. But they vary a LOT. Mine uses less than a qt. in a 4000-mi. change cycle. But here are my thoughts, FWIW: these oil-cooled motors are pretty hard on their lubricant, and you won't see many here using the 0W-40 weight, even though Porsche says you can. "Can" does not equal "should", and this is an area where Porsche treats its old air-cooled's like bastard stepchildren in terms of recommendations. I've never even heard of a 0W-40 dino oil, and I can't even find mention of it anywhere on the interwebz. Doesn't mean it doesn't exist, but why would he use about the most undesirable oil I can think of in there? I also personally wouldn't mix dino and synth - maybe to get you home, but I just wouldn't do it voluntarily, and i would change it as soon as I could.
I personally use a really good 10W-40 synth., some folks use Brad-Penn dino, some folks use Mobil 1, and then there's a myriad of other brands. These engine have special requirements that make otherwise very good oils not appropriate. They have "special needs" in chemical compostion, particularly in zinc & phosphorus to protect the cam & valve train. Take a little time, do a search (there's more info on here on oil than you could ever imagine
), and then decide.
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From: San Francisco, CA
I still don't really have a clear answer. What oil should I be using? What oil should I be topping off with? Somehow, I am even more confused now than when I opened the thread.
