Technical Blog:

What's the best engine oil for your 912? Conventional, synthetic, what brand, what weight?

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From: T.P. Stephens;  ; I have been driving European vehicles of many types since 1970. The last 8 years I have been making my living in maintenance/repair/restoration of European Vehicles exclusively. I ain't just a screwdriver jabber.
If the oil change interval is adequate for the way the vehicle is used, the motor can have 100,000 miles on it and the inside of the crankcase and valve covers are as clean as the day they were assembled. The capacity of the detergents in the oil to kept the contaminants in suspension has never been exceeded. If you see varnish beginning to build up on the rockers it means the deteregent is loaded and the contaminates are precipitating out to infect your motor. They continue to build up into a carbon/ tar layer that insulates the back of the pistons from the cooling oil and therefor begin to run much hotter than they were designed for. Eventually, chunks of carbon can be found in the pan.
If you change your oil and 100 miles later it is black again, it is proof posative that you have a heavy buildup of varnish that is immediatle dissolved by the fresh detergents and your next 2900 miles will be a rebuilding and replacement of the crud and of course further excessive wear of bearings, lifters, cam lobes, oil pump............aaargh.
I bought a new BMW R90/6 in 1976 and immediatly noticed air bubbles/foam on the dip stick with Quaker State. Changed to Castrol, same thing. Changed to Pennzoil, same thing. I had heard that Valvoline had a higher anti-foam package and tried that. Problem solved.
I started using straight 40wt in summers and 30wt spring and fall and had excess carbon buildup in the combustion chambers. Standard straight grade petroleum oils have a higher carbon content the higher the weight. Multi weight oil is made up of a base oil of the lower weight ie. 10/40 is a 10 weight oil with
additives to provide the higher weight characteristics. I switched to the multi weight valvoline and problem resolved.
When I got my 912 I tried Castrol as an experiment and guess what-foam. Switched to Valvoline and problem was again resolved. Note that Valvoline is marketed under a huge number of aftermarket names like NAPA, Car Quest and such. You can tell it is Valvoline by looking on the back. It will say Ashland Oil Co. or Mac's Oil, both in Lexington, Kentucky. Might as well use what works best by empherative evidence in small crankcase capacity air cooled motors at 99 cents a quart and available ANYWHERE.
Use multi-vis 10/40, 15/40 or 20/50 depending on your ambient requirements.
One of the good things about full synthetics is NO CARBON. I change my oil always before it gets anything like dark so synthetics are not really cost effective for my use. A good rule of thumb. Never add a second quart before changing, particularly in a 2 liter crankcase.

From: Leland J Olsen; ; Your question of the month on oil was a great one, I took Chris Smith's advice and put synthetic in my trans, couldn't find Redline so used Valvoline synth instead. Chris's comments on improvement were right on, I noticed immeadiately that the car shifts smoother, runs quieter and just feels better overall. Am still very happy with 20-50 synth you recommended for the engine, definite improvement but not as noticably dramatic as going to synth in the trans. Once again, thanks to your 912 Registry site my car has taken another step forward. Salute, Lee

From: Chris Hickson;  ; In the '80s and early '90s I taught motorcycle mechanics for Harley-Davison Motor Co and learned quite a bit about oil. I'm not a petro-chemical expert but I know a few things. First of all I think in terms of cost to benefit ratio ( a term I just made up). Synthetics are wonderful things and if you can get them cheap enough to still change your oil every 2-4 thousand miles, great. See it's like this, one of the big advantages of synthetics is it takes a lot of abuse before it breaks down to the point of not protecting adequately, we are talking 8, 10, even 15 thousand miles in a MODERN car. The 912-356 engines are not modern however and their big problem is OIL CONTAMINATION. So going back to that C to B ratio, I use a good quality oil designed for an air cooled engine (much more tolerant to heat than your average stuff) and replace it every 3,000 miles on my '69 912. The oil I use is Harley-Davidson 20-50 (their latest '360 grade'), it is designed for air-cooled, carbureted, high peak operating tempature engines that see alot of abuse from their "warm up, we don't need no stinking warm up" owners. It can be had for about $2.50 a quart give or take. Thats a bit more than your average car oil but it is a semi-synthetic with all the properties an air-cooled Porsche owner needs at a reasonable enough price to dump it every 3K miles. Think about it folks, H-D and 912, 356, 914 and 911 engines have more in common than Buick and Porsche engines. Chris Hickson in Seattle WA.

From: Chris Smith; ; I live in a hot 90-110 degree summer and moderate winter 35-65 degree climate in Northern California. I've tested  other oils but have always gone back to Castrol 20w-50 since buying my old bettle and 914 2.0 years ago. My 912E doesn't use any oil after a rebuild some 25000k miles ago. It runs way hot in the 90 degree and above summer temps. like most 912E's. I recently went to Mobil 1 at the suggestion of our local Porsche race/repair shop but I don't see a lot of change in temps yet. I went from Swepco in my transaxle to Redline synthetic which resulted in major gains.  Better shifting, quieter operation, cooler temps, better cold weather performance, and better mpg. Because of the gains I experienced in my transaxle I'm going to Redline in my engine. I notice at ambient temps above 90 degrees traditional oils get dark(burnt)and a little more sludgy between 3000 mi. changes. Synthetic seems to hold on a little better at these temps which might not be a problem in more moderate climates.

From: Robert Burn;  ; For 31 years I have changed the oil every 3000 miles with Castrol SAE 30 oil and am still running the original sized bearings after a complete rebuild in 1983 at 130 K miles. It now has 231 K miles. Bob Burn

From: Wendell;  ; Since moving to a very warm climate, I have started using Castrol 20-50. The most important thing is to check it every day before driving the car, and to change it every 3k miles along with the filter. Don't forget to clean all the old oil out of the filter housing-it gets pretty bad down at the bottom. And if you want oil pressure right away-and most of us do-fill the filter housing about half full of new oil before you put the new filter in. Best wishes from Redding, CA, gateway to Lassen Park & the Trinity Alps. Wendell Hartley, HikerDuke@aol.com

From:Peter Baldauf;  ; Yes, the omnipresent question, which oil? Well I may not be correct on this but I don't believe mobil 1 and the like were available when 912s were produced. As a result, I choose conventional Castrol 20w 50. I don't know, I think there is a certain amount of brand loyalty involved with choosing an oil. Perhaps a little superstition even. Besides, I never heard of an engine failing due to a poor choice of brand or the wrong color bottle or it doesn't work because Michael Schumacher doesn't use it. Anyway, I use a higher viscosity since I am in Alabama and the average ambient temp. during the summer is, well who knows, but it's HOT I assure you. According to my owners manual for my 944 turbo what makes a synthetic oil, synthetic, is a refining process. It's still a petroleum based product just chemically refined to be more efficient with fewer additives. If you read the back of a bottle of oil, you'll notice a grading system. "The efficiency of an oil is expressed, for example, by the API classifications which are divided into categories "S" and "C". The degrees of quality are expressed by the final letters in alphabetical order: The requirements for Porsche engines are API class SE/CC to SF/CD." Many oils exceed this requirement, so I guess my suggest you choose whatever oil looks best on your garage shelf.  Peter Baldauf PCA Heart 'o' Dixie Region

From: Charlie Cheatham; Thu, 4 Mar 1999; ; I think that as long as you stick with a good brand (don't mix) and use a good multi-weight, you engine will do fine. As you know, the engine is designed to use about a quart every 600 to 700 miles. As for synthetics, I haven't made up my mind on them. I put some in my Ford Explorer which had over 100K miles when I put it in. Up to that point I had changed the oil and filter every 3000 miles and had never had to add oil between changes. When I went to the synthetic I had the engine flushed and cleaned. With the synthetic you are suppose to be able to go 7500 mi between changes. Well, before I had 3000 mi on the syn I had to add a quart. Since then I have had a 7500 mi change and again I have had to add a quart before 3000 mi. I'm thinking the flushing and the new oil may have unseated the rings and is causing increase oil consumption, but this may be totally wrong. As for my 912, I use Castrol 20W40.

From: Dave Atkinson ;    Dear Rick, I use Castrol GTX 20W-50 as recommended by Duane Spencer. I change the oil after every event and I run an external filter and deep sump, which I think do more to protect my engine than the brand of oil.  Sorry I do not respond to more of these Q's of the month. I will try to contribute more as I really feel that the Registry is a great thing.
I participated in the Meadowbrook Historics this August (98), and was allowed to run in the all 356 class. This was a great joy for me as I don't usually get to run with them. I got to sit in ( ride in ) a track orientation session with Vic Skirmants, and got to race with a lot of great drivers. I bring this up because last week, the TNN show "My Classic Car" aired a segment highlighting 356's that was taped at Waterford during the same event. My car even got a couple of "flash by's" . Although I was a back-marker for the race, I learned quite a lot from the experience, and got on TV to top it off.
Thanks for everything, Dave Atkinson

From: Jeff Halstensgaard;   Oils are a very important part of the engine and therefore it is one of the very most important things to buy and maintain. I use Castrol GTX 10-30, I have used this since I purchased the car since I did not know what the previous owner had ran. One important thing I learned through many years of drag racing is that if you change your oils weight, from lets say a straight 20 to a straight 50.. it is not good to go back down to a lower weight due to the fact that the heavier oil makes your clearances larger. (rings, valve guides, bearings etc) and if you do go back down to a lower weight, you will probably get blow-by and leakage. Therefore multi-weight oil is my favorite choice. Choose one oil, one brand, and a specific weight (or multi-weight) and stick with it. At least until rebuild. If you have a fresh engine, synthetic is great, less friction, more horsepower. Jeff Halstensgaard 1967 912

From: brian reynolds;  ; rick, i use quaker state straight 50 in thesummer and same brand but 20 weight during cold weather.brian

From: Mark Price; ; Rick- I have found that Exxon Super Flow 5-30W seems to work out the best in my 912E. I have tried just about every brand of dinosaur juice through the years and this one seems to give the best most consistant viscosity and less blow by the old worn rings! If it was possible to build an air-cooled flat 4 that wouldn't leak oil I would consider putting AGIP SINT 2000 in the car ( I used this in my Italian car days when I was in to driving cars from hell) and it was great stuff. Since my car leaks a quart about every 4-600 miles I'll stick to the Exxon at $1.00 a quart from the discount store. Mark Price 76 912E

From: glenn schumacher;  ; Don't use synthetics. I've used Delo 400 (Chevron) multigrade for the past 15 years. Very superior oil.  Glenn P. Schumacher, Ed.D.

From: Jeff Ellis; Mon, 01 Mar 1999; ; QOTM- Oil; Have used Castrol 20W-50 since I got my 912 twenty+ years ago. I change the oil and filter every 3-4K miles. No problems. Noticed no particular build-up/sludge when I rebuilt it some ten years ago. Probably the most important thing
about oil is to choose a reputable brand and change it (and filter) regularly. Oil changes are
such cheap maintenance and almost inexcusable for not doing.
Am interested in synthetics but have heard that in changing over to synthetics in an engine that
is not new will likely result in leaks where there were none before whereas a new engine that
is run-in on the syn. oil will get the most benefit. Who knows... Haven't talked to anyone
with an older model that uses syn. oil.
Jeff Ellis

From:  Larry;  ; I used diferent types but I found Castrol Syntex to make the engine run a little cooler and the price is not bad , I have put about 2000 miles on my car in the last 2 months and the oil looks almost new.........Larry

From: JMarg700;  ; Castrol GTX 20w-50 or Amsoil racing 20w-50

From: Leland J Olsen; Mon, 1 Mar 1999; ; I took your advice and put Mobile 1 15-50 synthetic in my 1968  912. It's probably a psychological thing but I would almost swear  the car runs better: idles and runs generally smoother; quieter; and   definitely keeps cooler in traffic. This is a new experience and so  has not stood the test of time. Will let you know if anything good  or bad goes on as time gooes by. Salute, Lee

From: dave;  ; castrol 10w30
thanks again! dave

From: Alexander v. Wachter; Mon, 1 Mar 1999; ; For all my cars I use conventional CASTROL GTX 15/40 This is quite reasonable here in Germany, about 15 dollars for 4 liters. If your petrol-station is not aware of the small 1600cc engine, tell them that this engine does not need so much oil than a conventional 911 engine!! I got an overfill from the mechanic, you can imagine the mess in engine compartement and on the street 30 miles later.  Took me hours in cleaning up the mess! Regards Alex, Munich, Germany

From: Giolli, Florio; ; I use regular 20-50 racing oil and change it frequently. I guess the synthetics are the best but I like to change oil every two thousand miles and at that rate I would go bankrupt. Flo
Florio, Voice-Mail 1-800-227-4230 X8243

From: Carter Willey; ; I use Lubro-Moly Voll-Synthese 5W-40 in my 1968 912. My reasons for doing so, in order of their importance to me, are:
1- It's German,
2- It's Expensive,
3- I have been somewhat convinced of the benefits of synthetic oil.
I've been using this oil since I rebuilt the engine two years ago.
I use Mobil One in the transmission; shifts beautifully.
Carter Willey
Waterville, Maine

From: Jason Terada;  ; I run 30-weight Valvoline All Climate motor oil in my 912. This is a conventional detergent motor oil. I've been running Valvoline in all of my vehicles for years, and think it's one of the best motor oils around. Valvoline Racing motor oil is also excellent, but sometimes hard to find. The high detergent content of Valvoline Racing motor oil holds deposits in suspension, and prevents them from coating the inside of the engine. I avoid the use of motor oils refined from Pennsylvania crude. I have found that the high paraffin content of such oils tends to form heavy deposits.

From: McCohens;  ; It may not be the best but my choice is Valvoline 30WT, all year around. When it drops below 40 I use a magnetic heater on the case to warm it up.

From: John L.;  ; Consistent with the manual and with every ounce of advice I have ever heard, I have used straight 30 weight throughout my years with this car, changing it every 1500 miles, plus spring and fall, both before and after a rebuild. I find myself more than a bit skeptical of most comparisons among other products, as results really wouldn't seem terribly valid except over very long periods of time and car-to-car, and all prospective effects are so very subtle at best. I have also heard from some loyal PCA users of Slick 50 (?) and/or Mystery Oil (?) that these are effective, though I don't know how they can tell. As always, I will be interested to hear what fellow members have to say. Very best regards, John L.

New! 912 Registry Members can share technical information, add technical information, and access quality, up to date technical information on our 912 Wiki.