Been running 0W-40 Mobil 1 FS European Car Formula for 2 weeks now

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Dec 24, 2024
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My car is a fully built "racing" motor with forged internals and looser tolerances than factory. The first thing I really noticed which is a rather big difference is that before with either Penzoil Ultra, Rotella, or VR1 in anywhere from 5W-40 to 10W-30 I would have rather loud cold start with piston slap until the motor got up to temperature some and the metal parts had time to expand.

For some reason with this Mobil 1 0W-40 EU formula my motor has no piston slap that I can hear at all and overall the motor is much more quiet. I did not expect this at all...

Oh and my Moroso oil pan leaks A LOT more with this Mobil 1 than the other brands. In it's defense though I am using a different nylon washer so maybe that is the problem. We will find out next oil change.
 
Looser than factory? do you have the build sheet. m1 0w-40 tends to shear to a 30 but that's usually not an issue. If the oil temps don't go too high it might be ok to keep using.
 
I went from several years of using QS Euro 5w-40 to M1 Euro 0w-40 because QS is no longer on WM shelves. After a couple of months using M1 in the Ranger, it's going into everything I drive from now on. Remarkable, and unbelievable, difference.
 
Well...going from 5w-20 (Ford's stupid recommendation (and me being stupid)) in my F150 to a 10w-40 eliminated piston slap on cold start in the old 4.9L. :unsure:
I'm gonna stop you right there.

The only two things which generally cause "piston slap" are:
- improperly sized pistons to the bore
- forged pistons (which expand from warming up at a slow rate relative to the other components)
The F150 never had 4.9L engines which had either, in the 31 year run (1965 to 1996).

Whatever noise you're hearing, I seriously doubt it's "piston slap".


NOTE: The late 60s / early 70s did have some HD versions of the 300 six which did have forged internals, but those were only installed in very heavy service dump trucks, etc. Never into an F150.
 
I'm gonna stop you right there.

The only two things which generally cause "piston slap" are:
- improperly sized pistons to the bore
- forged pistons (which expand from warming up at a slow rate relative to the other components)
The F150 never had 4.9L engines which had either, in the 31 year run (1965 to 1996).

Whatever noise you're hearing, I seriously doubt it's "piston slap".


NOTE: The late 60s / early 70s did have some HD versions of the 300 six which did have forged internals, but those were only installed in very heavy service dump trucks, etc. Never into an F150.
Not that it matters but wasn't the 300 inline 6 4.9L available in the F150 in the early 90's?
 
Not that it matters but wasn't the 300 inline 6 4.9L available in the F150 in the early 90's?
Actually, it was available in the F series trucks for most of its run; from the 70s all the way until 1996 when that generation of F series trucks ceased.

The 300 six / 4.9L in F-150s never had a problem with improperly sized pistons, nor did it ever have forged parts.

My point was that ONLY the HD version of the 300 I-6 had forged internals, and that engine was ONLY put into the F600, F700, F800 chassis for dump trucks, box trucks, grain trucks, etc. The HD 300 I-6 was never fitted into an F150. By the time Ford was calling it by its metric name ("4.9L") that engine didn't have forged internals nor did it have piston size/bore issues. Whatever noise he's hearing likely isn't "piston slap".
 
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I started using it in my L92 and anecdotally would say the slapy slap is about the loudest it's been. I always ran 5w30 in the past because reasons, then upped it to Rotella T6 5w40, then QS 5w40 and now the Euro 0w40. Maybe if I move to Europe it will go away...
 
I'm gonna stop you right there.

The only two things which generally cause "piston slap" are:
- improperly sized pistons to the bore
- forged pistons (which expand from warming up at a slow rate relative to the other components)
The F150 never had 4.9L engines which had either, in the 31 year run (1965 to 1996).

Whatever noise you're hearing, I seriously doubt it's "piston slap".


NOTE: The late 60s / early 70s did have some HD versions of the 300 six which did have forged internals, but those were only installed in very heavy service dump trucks, etc. Never into an F150.
Well...After a little over 40 years of turning wrenches, starting in 1966, I can assure you I know what piston slap sounds like.

Second, #4 cylinder has a vertically scored cylinder wall. This is where my coolant was leaking. I discovered this while replacing the, notoriously troublesome, head gasket. This was back in 2003. I crossed my fingers and said seven hail Mary's and slapped it back together. Divine intervention must have prevailed because I've never had a problem with that cylinder since. Remember, this only happened when I used 5w-20 in cold weather and only on a few of the coldest days.

I appreciate your comments but took offense to you trying to school me without further investigation.
 
wow.....heated in here.

My car is a fully built "racing" motor with forged internals and looser tolerances than factory. The first thing I really noticed which is a rather big difference is that before with either Penzoil Ultra, Rotella, or VR1 in anywhere from 5W-40 to 10W-30 I would have rather loud cold start with piston slap until the motor got up to temperature some and the metal parts had time to expand.

For some reason with this Mobil 1 0W-40 EU formula my motor has no piston slap that I can hear at all and overall the motor is much more quiet. I did not expect this at all...

Oh and my Moroso oil pan leaks A LOT more with this Mobil 1 than the other brands. In it's defense though I am using a different nylon washer so maybe that is the problem. We will find out next oil change.
Did you start the engine in the same conditions? Same time since last start? Same temp? Using the same filter?

Maybe oil getting to stuff faster makes a difference. Maybe the sound you hear is something else similar to piston slap?

There is so much left up to debate that would be unprovable, as is the case with many of these kinds of topics, took me a while to realize this. The only thing you really changed was using a 0w rather than a 5w, by your testimony.

Glad you got the noise to stop. However it happened.
 
My car is a fully built "racing" motor with forged internals and looser tolerances than factory. The first thing I really noticed which is a rather big difference is that before with either Penzoil Ultra, Rotella, or VR1 in anywhere from 5W-40 to 10W-30 I would have rather loud cold start with piston slap until the motor got up to temperature some and the metal parts had time to expand.

For some reason with this Mobil 1 0W-40 EU formula my motor has no piston slap that I can hear at all and overall the motor is much more quiet. I did not expect this at all...

Oh and my Moroso oil pan leaks A LOT more with this Mobil 1 than the other brands. In it's defense though I am using a different nylon washer so maybe that is the problem. We will find out next oil change.
put the old oil back in,
run audio analysis in audacity or ocenaudio,
put the new oil back in,
run audio analysis in audacity or ocenaudio,
report back your findings here.
details matter, like your laptop, how far away it is from the engine. ambient temperature. how many birds are calling in the background. etc
keep a log, like how you were taught in high school.
 
Looser than factory? do you have the build sheet. m1 0w-40 tends to shear to a 30 but that's usually not an issue.
Zero to forty is quite a big spread. Plus, 30w oils can be in the 12s and that's still on the thick side.
But I know you know all this already.......

I'm a big fan of the M-1 Euro SP in 0w40. But even if it was 0w50, my 4k OCIs wouldn't show any engine problems, even if the viscosity dipped from 16 to 12 in those 4k OCIs. Oils today are loaded with VIIs and very few are complaining about it.
 
Well...going from 5w-20 (Ford's stupid recommendation (and me being stupid)) in my F150 to a 10w-40 eliminated piston slap on cold start in the old 4.9L. :unsure:
I would suggest that it didn't eliminate the piston slap, rather, it quieted the noise from the piston slap. Are you suggesting that the oil fixed the issue?
 
I would suggest that it didn't eliminate the piston slap, rather, it quieted the noise from the piston slap. Are you suggesting that the oil fixed the issue?
Dunno. Sticking with xw30 and xw40 oils made it go away. I don't think the oil fixed the issue but it eliminated the noise.

EDIT: I should have said, in my original post, that it eliminated the piston slap noise. Not eliminated the piston slap. Doh.
 
Changed oil recently in 2017 VW GLI and used M1 SP 0W-40. In the past, M1 in this grade has always been "noisier" with regard to start-up and valvetrain sounds than Castrol in same grade. Except the new SP version. Dead quiet. Even in the really cold weather we have experienced recently. Glad I bought a bunch of it.
 
wow.....heated in here.


Did you start the engine in the same conditions? Same time since last start? Same temp? Using the same filter?

Maybe oil getting to stuff faster makes a difference. Maybe the sound you hear is something else similar to piston slap?

There is so much left up to debate that would be unprovable, as is the case with many of these kinds of topics, took me a while to realize this. The only thing you really changed was using a 0w rather than a 5w, by your testimony.

Glad you got the noise to stop. However it happened.

Well now that you mention it, that is an interesting topic. I had been running Fram Ultra filters exclusively but this last oil change I went to Wix XP. But, with that being said I would get 85psi oil pressure with the Fram filters within 1-2 seconds so I don't think that was the issue.

The sounds I'm attributing to piston slap is the sound I would get only when going out to start the car first thing in the morning. Not really concerned with it, I knew I would have it going into the build. I just found it interesting I can no longer hear it.
 
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