What weight oil do you run in your boxster
11-27-2018, 06:59 PM
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What weight oil do you run in your boxster
Guys, can you please tell me what weight oil you run in your early boxster...The manual says 10W-40,...but from what i gather now, 0W-40 is also ok
Last edited by RVA; 11-28-2018 at 03:30 AM.
11-27-2018, 08:36 PM
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Search the topic & read all you can before making an informed decision.
11-29-2018, 12:48 PM
#5
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You need to understand what 10W40 and 0W40 means. The 2 oils at operating temperature are both 40 weight oils. The W means Winter. All the 0 and 10 indicate is the relative viscosity for cold starts. The 0 will be better for cold starts. If you only plan to drive in the summer, 10W40 is fine. If you are worried about oil passing seals or rings than a higher weight oil is in order like Mobil 5W50. When you consider many modern engines run W20 and W30 oils, W40 is already a high viscosity oil.
11-30-2018, 12:05 PM
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Porsche has an approved oils list which gets updated every couple of years. My local Porsche dealer senior tech would print me out a copy every so often.
There are a number of approved oils in different multi-viscosity grades available: 0w-40, 5w-40, and even one 5w-50. The only restriction on which of the 3 viscosity grades to use is in cold weather -- -25C -- Porsche says to use 0w-40.
I ran Mobil 1 0w-40 in my 2002 Boxster for approx. 300K miles of its 317K miles. After the RMS was replaced under warranty at around 25K miles the engine never leaked any oil other than when the spark plug tube o-rings were shot. A couple of years before the end of my time with the Boxster I switched to using 5w-50 oil for just a bit of added protection in extremely hot weather. Where I live/drive it doesn't get that cold but it can get up to and above 100F. (I never had a chance to know the oil temperature in either my 2002 Boxster or my 2003 Turbo but with my Hellcat even on mild days in city driving the oil temperature can climb to 230F. Dodge recommends a 0w-40 oil for this engine and that's what I use. Even at 230F oil pressure at idle is 40psi.)
Even with around 300K miles on the Boxster engine when I switched from 0w-40 to 5w-50 the engine never used any excessive amount of oil with 0w-40 in it. About a quart or so per 5K miles which is what it used from new. With the Turbo with either 0w-40 or 5w-50 I could never tell which oil was in the engine based on the oil pressure gauge. Hot idle oil pressure was as best I could tell the same with either oil in the engine. But the 5w-50 oil had better HTHS numbers than 0w-40 oil.
My advice would be to use Mobil 1 0w-40. But you can use any approved oil, a 5w-40 even a 5w50 (provided there is still one approved) but as I mentioned above in cold weather 0w-40 is what you should use. I would not even wait for temperatures to drop to -25C but switch to 0w-40 if the ambient temperature was often below 32F.
Given my usage with my cars I change the oil after 5K miles.
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12-01-2018, 11:12 AM
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Thank you for the time to reply, ...I understand porsche has new updates as to oil lists all the time , but the fact remains that the internal construction of the engine has not, bearing tolerances etc, are the same as they were in 99.....and back then they call specificly for 10w-40 and 15w-50....and as of 2016, now they say its ok to use 0w-40 for all cars back to 1984.....correct me if im wrong but bearing clearance etc was built to a tolerance and specific flow rate from the oil pump, i would think thinner oil would create low oil pressure and not provide a thick enough film to keep metal surfaces seperated.....Thats why i was nervious about the whole 0w-40 idea....but again i do thank you for your time to reply,....im thinking living in SC, with a 20 year old porsche the 15w-50 cant hurt, since we never see 20 degree temps.
12-02-2018, 02:15 PM
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Thank you for the time to reply, ...I understand porsche has new updates as to oil lists all the time , but the fact remains that the internal construction of the engine has not, bearing tolerances etc, are the same as they were in 99.....and back then they call specificly for 10w-40 and 15w-50....and as of 2016, now they say its ok to use 0w-40 for all cars back to 1984.....correct me if im wrong but bearing clearance etc was built to a tolerance and specific flow rate from the oil pump, i would think thinner oil would create low oil pressure and not provide a thick enough film to keep metal surfaces seperated.....Thats why i was nervious about the whole 0w-40 idea....but again i do thank you for your time to reply,....im thinking living in SC, with a 20 year old porsche the 15w-50 cant hurt, since we never see 20 degree temps.
Any decision on oil you make from that info will be wrong.
I don't have approved oils lists going back to 1999 but ones from early 2000s say the list of oils is applicable to Porsche sports cars back to, while I don't recall specifically, 1984 is about right.
Manufacturing tolerances and allowable bearing clearances have not changed materially from MY to MY.
The acceptable clearances and the tolerances necessary to have the acceptable clearances for plain bearings are really determined by factors such as bearing width, diameter, max rotational speed and these factors apply to your 1999 Boxster engine, and nearly every other engine made for a personal vehicle since a long time ago to now. This includes all the engines in all the vehicles I have owned. To keep the list short: 2002 Boxster engine, my 2008 Cayman S engine, my 2003 Turbo engine, and more recently my 2018 Mini JCW engine and my 2018 Hellcat engine.
The first number is the viscosity index of the oil at 32F. Thus 15w-50 oil has a viscosity index of 15 at 32F. 0w-40 oil has a viscosity of 0 at 32F. The takeaway is at cold engine start which is where a significant amount of wear *could* take place 0w-40 oil flows much better at cold start than 15w-50 oil.
(The 2nd number is the viscosity index of the oil at 212F. 15w-50 oil has a high temperature viscosity index of 50 while 0w-40 oil has a high temperature viscosity index of 40. Now you might think "50" is "thicker" than "40" and it could be -- I touch upon this below -- but when I switched from 0w-40 to 5w-50 oil I did not notice any difference in the hot idle oil pressure of my Turbo. At first I was a bit surprised but it occurred to me this makes sense the oil pressure not be higher. 5w-50 oil has a better high temperature high sheer number than 0w-40 and thus offers better engine protection at higher oil temperatures but the oil apparently flows well, is not "thicker", which is very important and I revisit this point below.)
If you are concerned about keeping metal surfaces separated at cold start 15w-50 oil is not the best oil to use. To cover something I mentioned in a previous post about cold temperature while in SC it doesn't get that cold I have to point out for those who drive in really cold temperatures Porsche says to use 0w-40 oil.
There is another concern about running an oil with a high temperature viscosity index too high. That is the oil may actually run hotter and break down in the bearings due to the increase in molecular friction.
The bearing clearances are very small, about 0.001. This thin film of oil is subjected to intense pressures and at the same time resides between two bearing surfaces, one of which is stationary while the other can be spinning at -- in the case of my 2002 Boxster -- 7200 RPMs. That's 120 revs. per second. Assuming a bearing diameter of 3" every revolution the total distance a point on the crank bearing journal travels is about 9.4 inches. 120 times 9.4 inches is 1130 inches or 94 feet. 94 feet per second is 64mph. Imagine two surfaces separated by just .001" of oil with one surface traveling at 64mph. And who knows that pressures the oil film is being subjected to in the engine.
Under these conditions the oil gets plenty hot. A too high viscosity oil can actually cause the oil's temperature from this friction to get to the point the oil breaks down. Thus one's attempt to keep metal surfaces separated by running a thicker oil than Porsche calls for can actually lead to metal surfaces coming in contact.
The increase in friction from the heavier oil is real: Some time back I entered into an exchange with the owner of an older air cooled 911 who insisted on running 15w50 oil even though I supplied him with a copy of the approved oils list from Porsche. The owner admitted that with 15w-50 oil in the engine gas mileage was worse and even his track times were slower but he still felt better with 15w-50 oil in the engine than 0w-40 or even I guess 5w-50 which is an approved oil as well. The decrease in gas mileage the increase in track lap times was due to the 15w-50 oil and the increase in drag that came with its use.
It is your car and you can run any oil you want I guess. But I urge you to run an approved oil. Porsche is the only authority on what oils to use in its engines. If one elects to ignore Porsche in this regard and choose an oil that is not on the list then he can choose any non-approved oil for any reason. Any reason yet all equally invalid.
12-04-2018, 09:18 AM
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wow, all very good points, and i did learn alot...i had no idea, bearing clearances were 0.001....and i never thought about friction from the oil being thicker...all good points, Thanks again.