Winter gas + low viscosity oil = knocking ?
 

My car developed early morning knocking when starting the car. I wonder if any of you have the same problem?

supposingly, low viscosity oil pumps better in the freezing cold (OEM 0W40 vs heavy side of 5W30) , but the winter gas maybe the contributing factor to detonation/knocking problem on my engine. Engine is a 2000' Mercedes M113 V8 engine with hydraulic valve lifters.

Any thoughts?

I can't think of any way a different oil would cause knocking, especially not a lower-viscosity oil in colder weather. I'd look for another cause that may be weather-related or at least weather-initiated... maybe an under-body O2 sensor damaged by the snow (not entirely sure how that would cause knocking either, just thinking about a sensor that could have weather-related damage).

I know they put antifreezing agents in fuel which does bring down their knock resistance. So while i'd make more power via feeding colder air to the turbos, i'd also lose power up to because of knock.

it's a 2000, so it's getting up there in age. add the hydraulic lifters into the equation, and they might be the culprit.

Where do you fuel up?

I mis-read that at first glance, as "Where do you feel up?" :haha:

Lower viscosity should not have anything to do with knock or detonation.
The cooler air means denser air so that might have something to do with it. But the knock, you said it was at start up, is it still there when you are driving? I would suggest it is your lifters due to lack of lubrication that is the culprit. The thinner oil stays thin in the winter and so there is a chance that the oil might have run down into the oil pan so the first few seconds after start up, there is no lubrication in the top end of the motor.

On other motors, I have heard of people who get timing chain/lifter noises when they run 10W30 but the noise is gone when they run 5W30.

I can imagine that slight knocking on the engine when it is not at operating temps is normal. that's the way my car is anyways, and it's a normal thing for 4AGEs to do that when they are first started up.

fill up at chevron 92 gas in Richmond most of the time....

the knocking last more than a few second.... it's more like a few minutes !

my car was knocking the other day too..
now its gone... duno why :S

If you gas it a bit when you start it up and the knocking sound occurs, does it go away?

Are you sure the engine is knocking or is it making knocking-like sounds?

chances are no...you're in Vancouver, not the Arctic Circle. I lived in Kamloops for 2 years, Grande Prairie, (Northern Alberta) for 1.5 yrs and now Edmonton...cars seem to do just fine in -55C, so I think you're dealing with a bigger problem than just the cold...

Its a 2008 Merc, take it to the dealer, tell them the issue.

If it’s Detonation that’s fuel/air related.

If it’s mechanical knocking (rod, bearing ect) that oil related, or you spun a bearing, something to that effect.

Try a couple of things.

1) Run the car down as low as you can on gas, then run a really high octane fuel. 94 octane should work. If the knocking goes away, the only thing I can figure is on start up the car has so much colder dense air going in that the computer cant compensate with the fuel for where it wants to burn, and your getting knock. That’s a LONG shot, but I guess it’s possible (although I have never heard of anything like it). Maybe the air becomes warm enough just as the car heats up from being heated in the manifold? But if a higher grade fuel fixes it, there is your fix. Although I would still ask the dealership why that is, as that seems pretty far fetched, even in my head. Detonation sounds like rocks hitting the underside of the car in most cases, its not really a “knocking” noise. And in a 2000 Merc, I would expect the computer makes detonation almost impossible. Maybe an o2 needs to be replaced, as its not reading correctly until warmed up?

2) Change your oil, and run what the manual recommends in this temp range. Most manuals will recomend diffrent oils for diffrent temps. Although most of the time the range is from -10 to +25 so you've got a lot of room. If that fixes it, then that was your problem. Just hope that it didn’t do any real major damage (although any engine "knocking" cannot be a good thing normally).

If none of this helps, take it to the dealership. I have absolutely no knowledge of hydrolic lifters, but I would expect if there where the problem you would be describing a tick, not a knock. However, any noise that just suddenly "starts" cant be a good thing.

My 2 cents

Heheheh, what's the commercial with the mechanic doing the sound effects? "Does it sound like brrt brrt zzz bang bang?" "Yeah, that's it!" "Oh yeah, we can fix that."

Record the noise on video and put it on YouTube so we can diagnose it :haha:

You haven't been around here the last month or so...

You assume too much ;) I have. It wasn't that bad.

I've just changed the oil to PP and looking for a short OCI. Knocking still audible in the morning. But getting a little bit more quiet than before.

haha, ya... this may have been intense for life long Vancouverites, but nothing compared to northern Alberta or the prairies.

if you are really concerned, and do not want to take it to the stealership, talk to eddy at flying tiger...im sure he can fix your problems.

I would give the parts or service department a call at a Merc dealer and ask if in that car they recommend different oils for different outside temps. I can’t imagine the mild weather we have making a difference, but I dont know much about Mercs in General. If you changed the oil and the noise got quieter, I would be worried and get it checked out for sure. Something internal is knocking, and that’s not good. I would change the oil to something thicker, and then take it to someone who knows these motors to have it looked at, the sooner the better.

It may just be something stupid that we aren’t thinking of, but from your description, it doesn’t sound good. Does the knock change pace with the car? Meaning when you get on the gas, does the noise speed up?

wait...how old was the oil in your car? If it's been there long enough, it would have broken down and not provided enough viscosity (not temperature related, but temps would have affected it that extra little bit to make you notice it).

Regular oil changes w/ synthetic ftmfw.

it could just be the fuel pump, since its working harder to warm up in the winter time. My car does this and is part of its normal characteristics