Can oil vapors cause engine knock?

[Nick814]

2019 Ram. 5.7 Hemi. 66k miles. Owned since new.

Or differently put, can it enhance the possibility

I feel the answer should be no, but right around the time i put in Amsoil SS 0w20, i started having issues. I have always used 89 octane, and always from a reputable station (BP, Mobil, and Shell), cleaners, and never had a problem in 5 years. Since, i have used cleaners, and made sure to strictly use top tier (Shell and Citgo) with no luck. So could the vapors from the pcv system and the Amsoil be giving me a problem? Seems silly but coincidences cant be overlooked. Going back to PUP next. Just something that popped in my head.

 

[SubieRubyRoo]

Knock sensor failed?

 

[walterjay]

I have never heard of that happening. I doubt it but to be fair I am not an engineer.

 

[PontiacHO]

2019 Ram. 5.7 Hemi. 66k miles. Owned since new.

Or differently put, can it enhance the possibility

I feel the answer should be no, but right around the time i put in Amsoil SS 0w20, i started having issues. I have always used 89 octane, and always from a reputable station (BP, Mobil, and Shell), cleaners, and never had a problem in 5 years. Since, i have used cleaners, and made sure to strictly use top tier (Shell and Citgo) with no luck. So could the vapors from the pcv system and the Amsoil be giving me a problem? Seems silly but coincidences cant be overlooked. Going back to PUP next. Just something that popped in my head.

Yes, if there is excessive blow by. Did the engine start using oil?

 

[Nick814]

Yes, if there is excessive blow by. Did the engine start using oil?

No. At 6k and hasnt seemed to use much at all, if any. Maybe stuck pcv valve? Exhaust doesnt smelly oily either.

 

[SHOZ]

Oil does reduce octane but you have to be in the visible smoke range I would think. Same weight oil as before?

 

[ARCOgraphite]

Ahh, the noisy old PAO at it again! j/k.

 

[kschachn]

You'd have to have hecka consumption to cause a significant octane reduction. And if that's the case then you would have significant combustion chamber and piston deposits that would be far more likely to cause pre-ignition pinging.

Something on the order of this engine I worked on:

 

[SHOZ]

You'd have to have hecka consumption to cause a significant octane reduction. And if that's the case then you would have significant combustion chamber and piston deposits that would be far more likely to cause pre-ignition pinging.

Yes as in smoke out the back.

Sounds like the knock sensors aren't working right as they should be trimming timing. If they are, it is out of the normal adjustment range for the tables.

 

[PontiacHO]

There is what’s called the “Hemi knock”. They have had a run of bad lifters similar to GM. Hopefully not that.

 

[kschachn]

There is what’s called the “Hemi knock”. They have had a run of bad lifters similar to GM. Hopefully not that.

So the “hemi tick” has progressed into the hemi knock? Whatever next?

 

[SubieRubyRoo]

So the “hemi tick” has progressed into the hemi knock? Whatever next?

The Hemi Shuffle, I assume

 

[ARCOgraphite]

You'd have to have hecka consumption to cause a significant octane reduction. And if that's the case then you would have significant combustion chamber and piston deposits that would be far more likely to cause pre-ignition pinging.

Something on the order of this engine I worked on:

View attachment 200174

Wow! what engine and how did that happen? I wasn't aware you lopped off heads! Is it back together and running well?

 

[wpod]

You'd have to have hecka consumption to cause a significant octane reduction. And if that's the case then you would have significant combustion chamber and piston deposits that would be far more likely to cause pre-ignition pinging.

Something on the order of this engine I worked on:

View attachment 200174

Lots of oil bypassing the rings of never blowing out the engine. Myself having Italian ancestry Italian tune ups are,,,,,, well genetic disposition I just can not help my self.

 

[Vitamin Yoda]

2019 Ram. 5.7 Hemi. 66k miles. Owned since new.

Or differently put, can it enhance the possibility

I feel the answer should be no, but right around the time i put in Amsoil SS 0w20, i started having issues. I have always used 89 octane, and always from a reputable station (BP, Mobil, and Shell), cleaners, and never had a problem in 5 years. Since, i have used cleaners, and made sure to strictly use top tier (Shell and Citgo) with no luck. So could the vapors from the pcv system and the Amsoil be giving me a problem? Seems silly but coincidences cant be overlooked. Going back to PUP next. Just something that popped in my head.

We got one with ~50K miles on it. I replaced the PCV valve (dirt cheap at O'reilly's) at 30K miles, just to be safe. I'm running Mobil 1 EP High Mileage 5W-30 in the 5.7 HEMI without issues. It also took care of a small oil leak. With your mileage, I would advise you to do the same, especially since the rear main seals on these HEMIs will let go at some point. The M1 EP HM 5W-30 is very low NOACK, high quality motor oil. PUP might be good, but it's not as good as the M1 I recommended for this application.

 

[SammyChevelleTypeS3]

You'd have to have hecka consumption to cause a significant octane reduction. And if that's the case then you would have significant combustion chamber and piston deposits that would be far more likely to cause pre-ignition pinging.

Something on the order of this engine I worked on:

View attachment 200174

YIKES!!!! That must have been interesting?
Or NOT in case you knew what you were going into. Almost want to say that must have been sitting for a while.
Engines can be so quirky and strange at times.
I have seen engines/cars sit idle for almost 10 years , then someone just takes off and runs minus ALL the precautions I asked them to follow or let me handle FIRST!
Ugh, some people are born with horseshoe tattooed to their back sides. . Of course some of them , they do not listen and just take off only luck out and get away problem free. Then there are those others..... not lucky who go almost no miles before the fail and then .... the wow!? Man! What happened?

 

[kschachn]

Wow! what engine and how did that happen? I wasn't aware you lopped off heads! Is it back together and running well?

It was a Honda engine with over 400,000 miles. After buying a junkyard engine which was almost worse (but sold as having less than 150,000 miles) I ended up rebuilding the engine for the guy. $2K later and it’s still running 5 years now.

 

[twX]

Are you getting audible knock, or are you just monitoring the knock sensors and noticing a lot of knock readings?

On modern engines, knock shouldn't ever really be audible since the sensors should pick it up and immediately retard ignition timing. I'd try a tank of 93 octane. If the sound doesn't go away, then it's probably a mechanical issue, not spark knock.

 

[Vitamin Yoda]

but right around the time i put in Amsoil SS 0w20

Another way to counter knock and run 87 octane in these HEMIs is to install a 180F thermostat. That would be the cheapest way to diagnose it as well.

It's hard to diagnose knock over an Internet forum. On some HEMIs the piston skirt coating wears off and they can have piston slap until the engine warms up. I'm not saying this to scare you, but I've seen it. Does that meant that the engine needs to be overhauled? Nope. Or you may already have that and the SS 0W-20 just exacerbated the issue.

However, you will not have pre-detonation issues in a port injected HEMI. The ECU is smart enough to retard timing to prevent that.

Try a thicker oil in that HEMI. It has the same bearing clearances and uses the same lifters and pretty much all the major marts as the 6.4. So you can easily go up to a 0W/5W-40 oil.

 

[Drew7a]

Try a thicker oil in that HEMI. It has the same bearing clearances and uses the same lifters and pretty much all the major marts as the 6.4. So you can easily go up to a 0W/5W-40 oil

The size of the bearing clearances have nothing to do with oil weight used.

If it pumps it will flow.