Here's another question...what the heck does outside temperature really have to do with the oil viscosity. I'm sure the engine runs a bit hotter since it can't cool as efficiently but the temp drop isn't that great from lets say an 80 degree day to a 100 degree day..so what kind of heat transfer loss are we seeing with a 20 degree diff of outside temp..for sure we personally feel it...but the car is running at 200F or so(factory thermostat)..and I have heard of oil temps of 240 F..so if the fans are pulling 100 degree air through the rad..vs 80 degree air through..is that really a big diff for the engine ??

just some curious questions..

later,
Tom
89GT

P.S. Just a personal experience note...put in 75degree thermostat when I did my last waterpump..and my running temps are way down...(we're talking running at just about 85C on my gauge) vs..90 to 95 C previously...and my oil pressure is now much better (I am assuming the better cooling is helping oil maintain viscosity).

 

Damn you two travel in pairs!
Very good point, thanks for the graphic.

I agree with this 100%.....but it needs to be used as a guide with old, worn engines (like mine).

My big question is this: if 5w-40 was too thin (clicking lifters) would 10w-40 work better........if (big if here) I was never fully heating up the oil?
So lets say just to keep it simple my oil never reached past 170F degrees, it's not reaching the 40 weight of either oil.
At 170F degrees, the 10w-40 will be thicker than the 5w-40. Correct?

The higher number is the thickness of the oil at 100 degrees celsius or 212 degrees fahrenheit. How thick is each oil at 170F?

We are not 100% copying that other thread.

 

Today I met a man named Paul Kent who is the owner of Kent Oil and also owns and operates an oil testing lab. We had a long talk about many things regarding oil, molly, and 928's. Yje one thing that he explained to me that may shed some light on this subject of viscosity is this. The way oil is made in a multiviscosity is that a polymer is used. These tiny polymers look like little hook worms when viewed under a microscope. Kind of like a collapsed letter C. The oil is actually the lower viscosity of the two #'s. The polymers expand or unroll when heated. This makes them larger and increases the viscosity of the oil. There is a phenomenon called shearing where these polymers are cut in half. Once this happens they are useless and you are left with a single viscosity oil. The viscosity of this oil is the 1st # in the weight. Meaning that if you start out with 5w-50 and then the oil experiences shear, you are left w/ 5 weight oil. He stated that this is much more rare with modern oils but it is the reason that caterpillar recommends a single weight oil in their engines.

I have no facts to back any of this up. It is just what I was told today. I will be taking an oil sample to him in a week or so. This will be interesting to see since I am also using the Mobil 1 0w-40 . After I get this baseline sample. If the analysis is good, I will be adding a Moly additive and then getting another test at my next oil change. It should be interesting to see if there is any difference.

Cheers

 

Hi,
Enzo - I am not worried at all that people may query any of my advice. I only originally contributed to this subject in 2002 because of the misinformation being spead about the Porsche OCIs being wrong. My 12 Used Oil Analysis results simple proved Porsche to be correct and with a huge safety margin when using a top of the range engine lubricant

I have had much to say on lubricants on RENNLIST over the last five or so years - and I am happy for any of it to be validated by any reputable Oil Company's Engineer(s) - not Sales people though!

I have not contributed on the subject recently as I have perhaps said enough already - If anybody thinks I should contribute then tell me!

I can confirm that Castrol's 10w-60 synthetic is a marvellous product for race engines - I helped to develop it in the late 1970s!

I use Delvac 1 5w-40 in my Boxster (in preference to M1 0w-40) and M1 0w-40 in my CLK - and I do NOT work for any Oil Company - at 68 I'm happily retired - and I miss my S4 dreadfully!!!

Keep the music playing.......................

Regards

 

so doug, what would be your preference in the s4? 10-40? 5-40? 5-10-50?

 

Please maintain oil-sanity for us all on this list!

I also really enjoy when you give 'behind the scenes' information on oil, something we/I would never hear otherwise.

 

When I was working for a Porsche dealership from 1977 to 1994 in Sydney Australia we only used what Porsche Cars Australia recommended in all Porsche models, and oils with a viscosity of 0w-30 or 5w-40 not only wasn't used they didn't exist . We were instructed by the importer to use what was then Valvoline Turbo V and it later was renamed Valvoline GP50 with fantastic results , No noisy lifters , No premature worn camshafts ,and NO thrust bearing wear AT ALL on any 928 of any year model . When I started my own Porsche repair business in 1994 I naturally carried on with what worked extremely well , and that was the GP50 which was a 25w-50 , We even went racing on the stuff and last year my son Sean won the Porsche Car Club NSW Drivers championship and the Supersprint Championship using the Gp50 in his 1986 Porsche 951 . We have noticed with some interest the modern Phenomenon of using the much thinner vis oils in Porsche engines from last century , and it has turned in a real money spinner for us , we probably work on more 928 models than anyone else in Australia and with the notes ( ledger) that I have been keeping for quite some years now on the year types of the 928 's that come in with destroyed camshafts / lifters , badly worn thrust bearings , and how can we forget the odd spun big end bearing , and what have we found ? . All the multitude of 928's that come in with these worn components have ALL BEEN RUNNING ON 5w-40 vis oils . And the ones which have stayed on a decent quality 20w-50 or a 25w-50 or a (15w-50 from 1992) FROM NEW have no wear issues at all . Don't get me wrong I am not complaining this has been fantastic for us $$$$$$$$$$ . And the best part I am not selling a thing , this is just an observation at the coal face with 30 years working hands on with Porsche cars , Remember IT IS NOT A GOOD THING to have your'e oil pressure warning light on at idle ( engine oil very hot in traffic ) and it only happens with oils like 0w-30 or 5w-40 , they just don't work in these older Porsche's." PS "make sure there is ZDDP in the 15w-50 or the 20w-50 , most of the thinner so called synthetics have no ZDDP , its important for camshaft life . ALL the oil companies should have the 15w-50 or a 20w-50 with ZDDP , We only use valvoline ( was gp50 ) now MAXLIFE 20w-50 etc . Regards . BB.

 

thanks jet951...this keeps getting better and better. so basically no matter what the hot weight you use, the 'base' weight should be a 15-20. makes sense.

 

Mega-Ditto's

I was pissed after switching to the lighter weight oil and hearing my lifters clacking. A good sign my engine is not entirely healthy. Sure running the heavier oil is a band-aid. It beats rebuilding the engine (for now).

 

Ever since I changed to Delvac I have had low oil pressure problems and like Jim M will be changing my oil in the next few days.
I never had a problem with Mobil 1 15w 50. But does it have the ZDDP??

 

One more thing. The oil engineer I spoke with also mentioned that the 0w-40 I am using is probably not the best for my hot climate. He recomended that I go to a 5w-40 FWIW. Once I get the oil analysis I will have some hard facts to go on and I'll p

 

Swaybar-
When was that TB issued? It must have been after 1993 as I don't see it in the 84-93 Technical Bulletin list on Jim Morehouse's CD's.

 

I find these kind of statements difficult to take seriously. How many is a "multitude"? 5? 500? "Worn components"? How worn? To failure? Or normal wear for an engine with 300k km? What kind of "5-40" oil? A quality synth? Or cheap dino? Way too many questions.
Doug Hillary's UOA's with Delvac 5-40 would seem to indicate just about no engine component wear, in direct contradiction to your "claim". I'm not sure how to square this.
Glenn

 

I have followed Doug's information with keen interest and that being the reason I changed to Delvac. I have about 20 gallons of the stuff in my workshop so I was totally convinced that this was the way to go.

I have also read BB's (JET951) comments about the oils and there effect on wear on the older cars. He is stating from actual experiance and also needs to be heard.

My experiance is very basic and certainly enough to make me change. Changing from Mobil 1 15W 50 to Delvac reduced my oil pressure significantly - 1 bar 14.7 psi. This has also heppened to other Delvac users.

Forget all the theory and go with facts. I trust Dougs research but facts are facts - my oil pressure has dropped NOT GOOD.

Maybe Delvac changed its formulation this year??

 

Andrew tried a different 5w-40 with the same results as you.