The 5w40 is a full syn, or at least it's Mobil competitor, Delvac 1, is a full syn in the 5w40 category and as it's approved for mixed fleet, works well in our engines. I personally think it's even better than M1, but that's just me.

Don't get me wrong, the 15w40 rotella T (non syn) is great too. I've used Delvac non syn and Delo non syn in the same weight grade in my 912 and saw decreases in my oil consumption and oil temp over Castrol 20w50 and even M1 15w50.

Charles Navarro
LN Engineering
http://www.LNengineering.com
Aircooled Precision Performance

1977 911s-2.7 engine w/total rebuild about 8000 miles ago. Broken in with Castrol 20/50. No leaks. First Mobile 1 oil change was 2000 miles ago. Prior to syn my car used about 1 quart per 600-1000 miles-sometimes more depending on? Thus far, on the Mobile 1, I am 1/2 quart down (approx) from the amount that was in immediately after the change. Why would this be? It is possible that because the last 2000 miles where put on during a trip that something works out differently, but I don't know what that could be. I 've driven the car often since the trip which was 3 weeks ago, and still no oil need be added. To me this is quite remarkable and totally unexpected. Also the car doesn't smoke as badly on start-up as it did on dino. Again-why? Also, no leaks so far on Mobile 1. Plus the car's 0-60 time have dropped by about 2 seconds. Okay-I'm lying about that:). No change in noise or performance. It has run cooler, but the fact that local ambient dropped after the oil change might have something to do with that.

These are simply observations, not opinions. I have used Mobile 1 in all my Volvos and BMWs. I never really noticed a difference in oil consumption, but they aren't as thirtsy as the flat six. I use Mobile 1 because I buy into the claims that it will extend the engine life by being more "slippery" as well as all the other syn propaganda. I figure it can't hurt.

My mantra has always been all-synthetic for new or completely resealed engines, and t-rex or at most a blend for anything else. I have experienced leaks twice when putting synthetic in used engines.

Ah Wil, I wasn't trying to argue the value of synthetic in the broad sense, but assuming that synthetics do provide more protection, those who would forgo that extra protection to save a couple of drips on the floor seem to have priorities askew.

Better engine protection vs. drips in the driveway was what I was commenting on.

BTW - I love that oil bible site! Thanks for that, it was awesome for my boat diesels as well...when I still had the big boat ;)

I agree with "1982911sc" as I've used Mobile 1 in all of my new cars (BMW, Infiniti, Acura, Honda...etc...) and never seen a drop of a leak. The engines look brand new after 70,000 miles (use a flashlight and look into the oil fill hole).

For a turbo, I wouldn't use anything but synthetic.

Emission says:

"For a turbo, I wouldn't use anything but synthetic."

Again...why? I understand the "generally" better high temp characteristics, but as I've said before.... IF ... you can use a straight weight mineral oil, there are high quality versions out there that will literally beat the pants off Mobil 1...increased flash point by 50-100 degrees , and much improved HT/HS characteristics.

My point is that most people (either) live in places like California where low temp pour point isn't a factor ( where this thread veered off before)...or they put their cars away for the cold weather....ending up with the same non-issue. That leaves only high temp operation and (granted) synthetics are very good in this regard..but there are certain, cheaper, mineral oils that are even better.

Wil

I am not going to put a straight-weight "50" in my block (I use M1 15W-50 now) and drive to the track.

I have seen my engine oil temps approching 250 F on the track. I can only imagine how hot the oil is under the turbine bearings if my case it that hot! It is that type of stress that synthetic oil shines.

Multi-weight Mobil 1 synthetic (or any synthetic for that matter) is the best overall compromise.

But doesn't 15w50 make more sense if you drive your car in a wide variety of temperatures? For instance I drive all summer and it might get up to 100 degrees F - I sort of put my car away for the winter, but if we get a good stretch of weather and the salt has been washed off of the roads I will go out for a 2 hr.drive and it might only be 25 degrees F. I shudder to think what that straight weight oil is doing in the sump for the fist couple of minutes on startup. :eek:

So I think that if you are only driving in a very limited temperature range a straight weight oil can work, it just doesn't work for me.;)

Jeez guys....let's try again....

SURE....a multi-viscosity oil operates better over a wide ambient temp range. That's why I said ( in Capital Letters, no less )... IF ......

IF ....your car runs as a summer car only...like a lot of us East coast guys...and certainly within the year-round use of California...you can go with a mono weight oil. Porsche itself was one of the last stallwarts in recomminding multi-viscosity oil.

And Emission....that's my whole point about high termp operation. Let me get this straight...you'd rather believe "words" ( synthetics have superior high temp characterisitics) than NUMBERS....Mobil 1 15W-50 flash point is 446 degreesF...not much better than an "average" mineral oil. Lesseee.....Mobil Delvac 1350 or 1650 50 weight MINERAL oil has a flash point of 554 degrees ( ! ). So much for "synthetic" having beter high temp characterisitics. !!!!

Wil:eek:

Since I am no chemist, I tend to look at what professionals are using in real-world situations...

Spacecraft use synthetic lubricants exclusively.
Jet aircraft use synthetic exclusively.
Most all race cars use synthetic exclusively.
Porsche, BMW, and even Corvette come with synthetic factory fill.

I don't think the issue is "better high temp characteristics" as so much "better high temp stability and recovery" characteristics.

Heat both to 500 F. for an hour and see which one survives. I am sure one (mineral oil) will be cooked.

You'd be wrong.... acording to the specs...that's my point.....Mobil one would have exceeded its flash point if operating at 500 degrees...Delvac would not ,...and Delvac would have about 50 more degrees in reserve.

The examples you cite have as much to do with wide range of *ambient* ( surrounding environment) temps, than it does with high *operating* temp.

Don't misunderstand me...synthetics *in general* have good high temp specs..however it's simply not true that they are exclusively better than mineral oils. These specs ( from the manufacturer itself) bear this out.

For the oils I quoted, Delvac has Mobil 1 beat in flash point and is also competitive in HT/HS ( high temp/high shear) characteristics. The reason its not loaded as factory fill is exactly because the high mono weight oil can't take ambient temp extremes as well as syn. ( low temp pour point is very bad...agreed).

Wil

Mobil 1 was originally formulated to deal with low temps. The Hight temp protection came much after.

They don't show stats on the site but state:

"Conventional motor oil is made up of an inconsistent mixture of long and short chains of carbon and hydrogen atoms. In the extreme heat of an engine, short-chain molecules can evaporate, and unstable molecules can oxidize and break down."

"Superior protection under heavy engine loads/stresses, such as hauling and towing.
Minimizing oil degradation.
Faster lubrication at start-up in low temperatures.
Superior protection at high temperatures.
Superior resistance to thermal breakdown.
Greater resistance to oil oxidation (thickening)."

Since I posted earlier about switching back to dino after the leaks developed (and I 'assume' you might be referring to my post), we'll just have to disagree :). I don't for a minute believe that I'm getting any less protection changing the dino oil every six months. I never see the temperature extremes where synthetics might provide 'better' protection imo. I've had a couple of top notch mechanics (who know more about these cars than I ever will) recommend what I now use (Kendal GT1 20W50). I think it's more important to do frequent changes (due to the hydroscopic/hygroscopic properties of oil), and with all that being said...I'd rather NOT have leaks :)!

Nah Keith, it wasn't really directed at you specifically. It's an argument that comes up often not only with P-cars but most automotive forums.

If you're basing the decision on what you believe is better for your car (which it sounds like you are) that's one thing, but if you think synthetics DO offer better protection but don't change because you don't want some drips...

Well that's where I wouldn't see the point.