dallasboats

I had the dealer switch my oil from 0w40 to the 15w50 at the last service. The car is not used much and used to make the clacking sound at startup from time to time. I've noticed this never happens now with the change of oil. However, I've also noticed the car does not rev like it did before. It still revs good especially once heated up for half an hour or so but before it was gangbusters couldn't get to the next gear fast enough.

Anyways, I thought some might like my insight on the oil. I'll probably switch back before too long but you never know, maybe I can find something in the middle. I do think the car is safer with the heavier oil and my infrequent driving.................

wross996tt

Try using what is recommended by the manufacturer....5W40 or 5W50...rather than what is suggested by the self proclaimed oil guy...(you know who I mean).

1999Porsche911

Many dealers are using 5W50 or15W50, especially in the south. You should not have reving problems due to the change in viscosity. Typically, an overfill of oil will cause sluggishness once warmed up. (any oil weight). The 0W40 is simply too thin an oil in warmer climates and increases your chances of valve wear (amoung other things).


If you like to hear you valves at startup, go back to the Mobill Water weight. I would use a minumum of 5W50.

Russ Murphy

"The 0W40 is simply too thin an oil in warmer climates and increases your chances of valve wear (amoung other things)."

How do you know this to be a fact?

dallasboats

1999, all I'm saying is I noticed a change in the revving of the car. The noise went away so I know there is a difference................... Maybe the 5w would be better for me. Porsche put the 15w in but complained about it prior. The car runs fine and is not sluggish especially once warmed up. Also, the car is not overfull. It's a great running car with either oil but I do notice a difference in behaviors.

1999Porsche911

Listen to your engine.

Russ Murphy

I can listen to my engine and make assumptions just like you. You state several points about the inadequacies of 0W40 Mobil 1 as fact in multiple posts. Where is the data from which you derived these facts. Look... I'm being a bit of a putz about this but I'm not trying to **** you off. I'd really like to know if your position on this Mobil 1 water thing has anything to do with hard facts.

dallasboats

I agree but also wonder if the 5 w might be better suited. Also, is the lucas addivtive a bad idea? My ford expedition has made that sound for years at startup. The mechanic always said normal, it's still running. I recently put the Lucas gunk in there and it no longer makes that sound. It's thick crap and I don't know I'd like it in my car, but it did make the sound go away.

1999Porsche911

I'm confused. In your orginal post you stated "but before it was gangbusters couldn't get to the next gear fast enough" which leaves the impression that is does not perform as well now. Weather you are running 0W40 or 15W50, there should be no perfomance differences that you can feel once the engine is warmed up. Your lifter noise is reduced or eliminated because there is less bleed down in the lifters than when you were running the Mobil Water. Now when you start your car, the valve mechanism is fully primed and the valve train is tight. This is good. If you have too much bleed down, the valve train is loose and you will have metal to metal banging until the system becomes fully primed.

If you go to the 5W50, you may still experience valve noise on the hotter days due to bleed down. If I were where you lived, I would run the 15W50 you currently have in the engine. I run this weight in summer in Chicago.

The reason I mentioned suggishness with an overfilled crankcase.....this is the big contributor to oil related damage to the engine because of increased pressure and airation. Put a quart more oil in the engine than it should have and you will see as much as a 5% decrease in engine performance simply because of the increased drag on the crank.

For those that doubt this - next time you dyno your car, throw in an extra quart of oil and watch your numbers drop.

dallasboats

No, once the car is really warmed up, after a few high speed revs, it feels similar. It's mostly just at the beginning as I exit my neighborhood and enter the first real road. This is where I notice it the most. I think it pulls a little power out but not sure how much. I feel like I can feel it but I'm not a Jedi either.

Tbred911

I noticed the same as well... there is some horsepower loss with swtiching to a thicker oil which will affect your acceleration; this is well documented on an engine dyno while comparing different oils.

1999Porsche911

I've posted many reasons why on this forum if you care to do a search. I have yet to find anyone that will answer the question "WHY is 0W40 better for your car". Seems to me that the only reason is because Porsche says so? Tear down an engine that uses too thin an oil and if there are hydraulic valves, you find alot of slop in the tappet cylinders, scouring of the journals, and of coarse, the ever continuing seal damage. Don't forget the oil blowby when the oil temps gets 240F+.

Want to reduce or eliminate the 2800 - 3200 rpm jerkiness caused by the variocam engagement? Want to reduce oil burning (increase HP)? Want to reduce or eliminate valve noise (which means wear) at startup? Want to better protect your engine seals? Want to lower your oil temps? Want your engine to last longer?

Get rid of the 0W40 in warmer climates.

Even Porsche DOES NOT recommend 0W40. It is simply one of the approved oils. If, in fact, 0W40 was the oil of choice, Porsche would only approve 0W40 for their engine and not even list any other oils...wouldn't they? For what reason do they list a 50W oil as approved? For what reason did some 996's come factory filled with 15W50? Seems to me that Porsche made a mistake...either orginally or now.

Russ Murphy

"I've posted many reasons why on this forum if you care to do a search. I have yet to find anyone that will answer the question "WHY is 0W40 better for your car". Seems to me that the only reason is because Porsche says so?"

I've read many of them. They(Porsche) likely have data.

"Tear down an engine that uses too thin an oil and if there are hydraulic valves, you find alot of slop in the tappet cylinders, scouring of the journals, and of coarse, the ever continuing seal damage. Don't forget the oil blowby when the oil temps gets 240F+."

Have you torn down a M96 motor that used 0W40 predominately and seen such slop and scouring? What's the temp at which blowby occurs when you switch to the 50W?

"Want to reduce or eliminate the 2800 - 3200 rpm jerkiness caused by the variocam engagement? Want to reduce oil burning (increase HP)? Want to reduce or eliminate valve noise (which means wear) at startup?"

I have none of these issues now. I'd think you'd have to be burning a lot of oil to actually increase hp by going to a heavier oil. In fact I doubt it is possible - but I'm just making an assumption.

bgiere

OMG, I used to try to counter some of the mis-information on oil...i surrender....1999porsche911,please don't take this the wrong way because i see that you do have some useful info occasionally, but you are totally misguided on this one....

1999Porsche911

Well, you have my recommendations from 35 years of exoerience, but run what you want. If you have no problems, then, by all means, stick with what you are using. If you are burning oil. having valve noise, leaky seals, jerky variocam engagement, then, why wouldn't you try a better oil?

So, like I always ask...why did Porsche recommend 15W50 for the orginal 996's? Why did they recommend using nothing less that a 15W40 in temperatures above 90F? Did the SAE ratings change? Did their engineers make a drastic mistake filling their engines with 15W50. Did all those car's engine blowup because of it?

We know for a fact that Porsche screwed up big time with their oil recommendations. The question is when? Now or then?