mark kibort

So, I know we have beaten down the oil topic, but in my mind, proof is in the end result.

one more story. the 6.0 liter S4 was dropped off a few months back and ive been driving it every weekend, along with the race car, and tuning, fixing, and getting the thing back in shape. however, every time the car is started, it sounds like a rod bearing is pounding itself out! or maybe a stuck lifter. got some pics of oil pressure at full temp, and 2500rpm and its below 5 bar. 5 bar doesnt happen to over 3500rpm. didnt think much of it, as it is a pure street car (been tracked only a few times in DEs). its got Mobil 1 in it. the owner was getting real nervous when i was saying what i was hearing, and that i dont like the "other brands " of oil in the 928. he wanted me to change it when i got it, but i didnt want to fit the bill for a $100 oil change. since im driving it more, i thought it might be the least i could do.

fast forward to last night, and i put in 9 quarts and a new Mahle filter of Amzoil 20 50 street oil with "zinc". WOW, is all i can say. it sounds like a completely different car. keep in mind the previous oil was in for less than 4000miles and about 1 year old. we are talking night and day! expecially on a cold morning, the car sounded like something was really wrong.. Now, its tight, no clicks rattles or any forengn noises. oil pressure is at 5bar at as low as 2500rpm now, even on a real hot day like today.

another thing to mention is that i have exclusively used the mahle filter, as the Mann filter doesnt look the same , internally. maybe thats an issue if the Mann filter is more restrictive in some of the engine failures.

Bottomline, my racer is still using Amsoil and has shown no signs of any issues, burning oil , or stuff in the filter for many years now, all the while, racing near once a month in a full beating session, where every shift is near redline.

never thought that oil would make that much difference in a car with some real bad rattles and noises in the engine, BUT, it did. ill continue to monitor it as the oil ages, but i am willing to bet, the 928 just needs this kind of oil to run and survive!

MK

Racing next week!!

namasgt

you said you heard what seemed to be a rod knock. Did you open the old filter to see if there is any metal chips in it? Who built the engine?

atb

Mark,
Why don't these guys sponsor you yet?

Mike Simard

A heavy oil can seem quieter but is more prone to rod bearing failures.

Seeing high oil pressure when going to a heavy oil is a classic false sign of what's going on. The gage pressure is high because the oil is bunching up at the sender and not getting to the rod bearings.

You can add some STP or whatever the amsoil version is and report record high pressure readings and quitnness! When the rod bearings fail you can blame it on amsoil not having been used by the PO it's whole life.

Bill Ball

With M1 in my car I get 5 bar by 2K RPM hot. I have 242K hard miles on this motor and never get any rod knocks of other odd sounds. Something is wrong with that stroker. Amsoil is masking a problem.

dcrasta

Is this the same stroker that had the mystery tune and mystery fuel pressure problems? Dumping fuel in the oils is bad, thins the blood, leads to spun bearings and knock..

mark kibort

filter is going to be cut open tomorrow.

I have my last filter from last week to be opened as well.

Also found out some more information on the suspect 6 liter. when the PO added oil, he was using 2050 GTX castrol, becasue he was thinking it was going to be changed out soon. He had an old case that had been lying around for a bunch of years. anyway, the oil was bad, so was what was added beause, without a doubt the amsoil, at the correct weight range, quieted the engine down.

i dont think the heavy oil in our case, causes rod failures, as my racing would have proved to be end of the motor if that was the case. and we are talking several motors. instead, a stelar record of reliability and oil analysis throughout 15 years of racing the 928, at better than 10% slower than the fastest of the fast GT3 cup cars since 1999 on slicks.

i think there are some oils that just dont cut it, and dont cut it at the high temps, you will never get on the street, vs the track.

as far as the noises, it might have just been crummy, old mixed oil, that was not staying in the lifters when the engine got cold. all i know now is that the engine starts after not runniing for a day or two with none of the noises that werer plaguing it .

Bill, i dont know if you remember when it first started up, but i was very noisy until the engine got to temp.

anyway, just an observation.

Speedtoys

Mark..I kinda gotta agree:

"every time the car is started, it sounds like a rod bearing is pounding itself out!"

That's the problem, not the oil that was in it. Thousands of 928s with ****ty oil in it..that dont do that.

Z

I agree completely. I'd never use some of the weight oils that I've heard of people using in their 928, unless I was trying to make things seem more normal until I got around to rebuilding the engine.

Used car dealers trying to cover up engine problems have been putting in thicker oil, or addtives to thicken it, ever since there have been used cars with mechanical problems.

If the oil pressure is low, there's a problem, and that problem is rarely the oil that's being used. Using thicker oil will give higher oil pressure readings, which seems to make people feel better. People like to see high oil pressure readings so much that some auto manufacturers put fake oil pressure gauges in the cars that they build. Basically they're like an oil pressure idiot light disguised as a gauge. As long as there's oil pressure above the minimum, the gauge reads a nice high number, that was probably selected by somebody that's part of the marketing department. I can't help but think of how much happier some people would be if their 928 had one of those fake gauges.

The oil pressure sending unit is located before the filter and bearings, so is just showing you the pressure there at that location. It's not telling you anything about the pressure or quantity of oil getting to any of the bearings. The oil pressure at your bearings is lower than what your gauge is showing. The thicker the oil, the lower that pressure at the rod bearings is compared to what the gauge is showing. If some people knew what was really going on at all of the bearings, especially with the oils that are being used by some people, they'd probably never start the engine again.

Mrmerlin

smart money would have the pan off to inspect the rod bearings
if they are shot then the mains should be inspected,
good luck with the oil filter inspections
if any have metal in them it is a good idea to inspect the rods

Dan87951

Shell Rotella T6 5w-40 has treated me well.

Pyzik

Ok so what oil would you guys recommend , m1? What weight? It's a hot day here in Chicago today(87degrees) and my pressure was at 1.5 bar at idle , this is my first summer with the car so I'm not sure if thats normal or too low? About a month ago at temp around 65 and when engine hot it didnt go lower than 2bar. When engine cold it's at 5bars and hot 1.5bar.

Mongo

Stick with 20w50 or 15w50 if Mobil 1.

I'm actually debating on switching from Mobil 1 to Valvoline Synpower. Supposedly there is more zinc in that oil, which is apparently good for engines.

Pyzik

That's what's in there now 15/50. And how much oil full level or between two lines on stick ? Should I worry about the pressure?

danglerb

I'm not sure about oil, but decaf might be a good idea.