Best Oil for 2.7 CIS?

Adam · Adam's Garage

I should preface this question by saying that I don't drive my 911 every day. It's currently at home and I have no idea what kind of oil is the best for it as it's due for a change.

I'm sure that I can get the oil specs as soon as I get home from work tonight, but I work at a car dealership and can organize the oil & filter and book the time for the guys here to do the oil change. I really should do it myself, I know!

I would prefer to run a mineral oil in the car as I don't like the reports I hear about boxer engines and fully synthetic oils. The oil we use here is 10W30 and I can get it for free, but, of course, I don't mind paying for the correct oil. If 10W30 is ok, then it's simply added convenience. My engine is only about 7,500 kms old (4500 miles) since it's total rebuild and has already had an oil change. It does not leak. Is a thinner oil ok for this kind of motor?

Thanks!

Jim Sims · 01-10-2002, 10:27 AM

Adam, I use Castrol GTX 20W50 (a mineral oil) in my '76 2.7 and change it and the filter (I use a Mahle OC54 as I recall) every 3000 miles or 3 months (4 months in the winter when its in storage). IMO a 10W30 is too light given the temperatures one can see running in hot weather. I have declined to use synthetics given the possible seal compatibility issues plus I live in a dusty area and therefore don't like the idea of leaving the oil (and dust - air filters aren't perfect)in for 15,000 miles (two years of driving for me).

Jim

Craig · 01-10-2002, 11:19 AM

Adam,
I have to agree with Jim that 10-30 seems light for the engine.
I have a 77 2.7, and use Castrol 10-40 in the winter (now), and then switch to Castrol 20-50 for the summer. I seem to hit the 3-4000 mile mark right about spring and again in the fall, so I just change the oil then. Since it is summer for you right now, you might want to switch to 20-50 right away.
Filter is Porsche, from the local Porsche dealership.

Craig

Adam · Adam's Garage

Thanks Guys,

Normally my mech does this for me, but he's taken some extended holidays. The guys here at work have no clue as to what it should really have. They suspected that 10W30 would be too thin.

It's funny, we've had a pretty mild summer by our normal standards (for Melbourne) and only in the last couple of days the temperatures have soared up into the mid-30sC.

Thanks for the info. I'll organize some 20W50 today. While we're at it, is the oil thermostat difficult to get to or to change?

Jim Sims · 01-10-2002, 01:34 PM

Yes, the one on the engine requires at least a partial engine drop maybe a full one. The thermostat for the external oil cooler if you have one, is contained within an aluminum housing whose threads tend to corrode/gall together making disassembly difficult. Why do you think your thermostat needs attention; overheating? oil leaks?

Jim

emcon5 · emcon5's Garage

Quote:

Originally posted by Adam Chaplin
I don't like the reports I hear about boxer engines and fully synthetic oils.

Please elaborate. I have heard people complain about synthetic oils with old seals, but never anything specific to boxer engines.

Tom

Adam · Adam's Garage

emcon5,

I work at a Subaru Dealership. Obviously, our guys work on nothing but boxer motors all day long. The general concensus is that Synthetic oils aren't the best for boxer motors, at least not in the early days of the motor's life. Especially if the car sits for most of the week awaiting the good weather on the weekend!

Of course, the boxer motor lets oil seep past the rings whilst it's sitting and then starts on lubricated (lower) bores, which is good, but when it's Synthetic oil, the car just doesn't get a chance to run-in properly.

Usually, they contain a high soap content and don't allow the piston rings to bed in properly. I've asked around and quite a few P-car gurus tell me that I shouldn't be using a Synthetic oil in a new or freshly rebuilt 911 motor until after 25,000kms.

I think this is a sound argument, but I'm open to alternatives.

JimSims,

My car seems to have a problem with the thermostat. It takes forever to warm up properly, but then doesn't really cool itself. On a warm day in traffic, it gets quite hot. I was concerned about temperature and after a drive where it got very warm, I reached uner the guard and checked my external cooler. It was stone cold. Sounds like a "partial drop" is on the cards! D'oh!

jay castriotta · 01-10-2002, 05:09 PM

So is it okay to use a synthetic oil after its broken in or do most not recommend it at all? I was thinking of putting it in my 3.0.

pjv911 · pjv911's Garage

Still waiting to hear from Warren , John or Otto on this thread. I too would like to know what is recommended. No offence to anybody`s previous post`s I just don't know anyone who knows more than those guy`s.

Kurt

Matt Holcomb · Matt Holcomb's Garage

Adam,

Have you considered using Shell's semi-synthetic oil? It's what's lubricating Crom's engine.

Matt Holcomb
1974 911 Carrera 2.7 Euro
1975 Mercedes-Benz 280SE
Dedicated Homepage
Engine Rebuild Homepage
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Matt Holcomb · Matt Holcomb's Garage

Adam,

Oh, let me know if you still want to take some spanners over to Mike's and give him a "hand".

I can't believe he didn't insist on replacing the thermostat before he put the engine back in the car.

Matt Holcomb
1974 911 Carrera 2.7 Euro
1975 Mercedes-Benz 280SE
Dedicated Homepage
Engine Rebuild Homepage
Porsche Owners Gallery Profile
Pelican Gallery Profile

Jim Sims · 01-10-2002, 08:00 PM

I want to clarify what I mean by an external cooler and thermostat housing. The external cooler has a thermostat housing in the oil lines just in front of the right rear wheel with the line running forward to probably a trombone type turn around loop (your "external cooler"?) in the right front wheel well. If it's this systems' thermostat that is not passing hot oil to lines forward of it I'd fix it first before dropping the engine. One doesn't have to drop the engine; just hope the thermostat housing can be opened up. Check the temperature of the oil lines behind and forward of the external oil cooler thermostat when the engine is good and hot.

Jim

Adam · Adam's Garage

Jim,

I like the sound of that compared to dropping the motor!

I'll take it out for a spirited run tonight before our predicted thunderstorm and give it a workout! I'll let you know how I fare. Keep your fingers crossed for me!

Matt,

I'd love to have a few kind words with Mike, really. Perhaps show him some some pictures of people's broken thumbs...

What kind of a tech totally rebuilds the motor and then fits it with a dud thermostat? (I bet he re-used the old one, the cheapass!)

65-911 · 01-11-2002, 07:44 AM

I am no expert on this topic, but if the car has the thermostat in the fender well, I believe where the thermostat goes in the engine has an insert to let the oil flow without any restrition, and no moving parts.

I took apart a 1977 2.7 and that was what was there.

So and engine drop should not be needed.

I am just throwing this out there, so they may not be 100% correct.

Have a good weekend.
Bruce

Jim Sims · 01-11-2002, 08:58 AM

Interesting. If the the engine mounted thermostat was removed and replaced with some type of fixed insert with its own top mounting flange (I seem to recall the top mounting flange is part of the themostaat but I may be wrong?) then (depending upon the insert passageway arrangement) the oil may immediately be directed to the engine mounted oil cooler even when cold at startup. This would prolong the time required for the engine to reach correct operating temperature. In really cold weather it might never reach operating temperature. I really doubt the engine mounted thermostat should be set-up thus way for normal use. However, if Adam's car is this way then this arrangement combined with a malfunctioning (non-opening) EXTERNAL oil cooler thermostat may explain taking a long time to get up to temperature and then not cooling properly when hot. Perhaps in the past instead of repairing the external thermostat an "expedient repair" was made by pulling the engine mounted thermostat and installing an insert (complete with a top flange?) or the engine mounted thermostat is just stuck open (more likely IMO). Adam, You may be looking at replacing both thermostats.

Jim

marcesq · marcesq's Garage

Factory manual for the 2.7 calls for SAE 30 during the summer and SAE 10 for the artic air zones.

I run Mobil 1 10w-30 with no appearent problems, rebuild is 60k young.

For what its worth.

jay castriotta · 01-11-2002, 05:47 PM

Marcesq-curious, do you drive your car frequently or infrequently?

marcesq · marcesq's Garage

Jay:

I drive it daily until first salting (which was a week ago here). Thereafter oil is drained and the winter projects are completed. Valves, a couple of oil lines, and suspension bushings all around.

I will not take her out unless there is no sign of salt or sand, and that would be just to keep things lubed up.

Regards

jay castriotta · 01-11-2002, 07:14 PM

Thanks for the reply. I don't drive mine often so we'll see. I'm probably going to give it a try. I'm surprised there hasn't been more input. This is usually question a lot of people have strong opinions about. I know in racing its a constant source of comments/suggestions.

Adam · Adam's Garage

Jim,

If that's the case with the thermostat then I'll definitely be having a "personal moment" with that previous wrench. Infact, I'll smear him from hell to breakfast as he's had quite a chequered past in regard to this car and other (more prominent) 911s. The guy's a cowboy and I haven't taken my car there in the time I've owned it.

Anyhow, I just got home from a quick trip (around 40 mins) and checked the oil lines, like you suggested. The temperatures seem to stop abruptly at that engine mounted oil cooler. I'm hoping that it's the thermostat there that is in need of attention! I'll pick up a thermostat on my next day off (Wednesday) and try to fit it myself. I hear that I've got to be VERY careful with those oil line fixtures as they can seize and I'd wind up shredding the threads on them. I'll soak them with WD40 or something and perhaps attempt the task while the motor is still reasonably warm.

Wish me luck!

Marqesc,
I'll probably switch to Mobil1 after the 25,000kms period. Thanks!

Jay,
Mine is a weekender. I rarely drive mine during the week and only really get it out in good weather. It's not a car that sits forever, but I don't deliberately take it out in the wet.