moving from 10w-40 to 5w-30. isit okay?

[TbM]

thats a harsh way to say it man, i still don't get why people get so angry on forums :/

in some ways you are saying the same thing that I did in different words, thickness or "weight" and "strength" are words I'm used to using so people understand it easier. yes the "w" is the thickness when cold, therefore the natural thickness of the oil itself, correct?

if the second number is the thickness when hot, doesn't that also reflect it's ability to not burn at high temperatures? the strength?

however this can be argued as I've read that oil thins out when it heats up. :/ confusing stuff.

No the w is not the natural thickness its the oils viscosity at low tempratures. ie cold starting viscosity.

No the second number doesnt mean its more resistant to burning, it means it wont thin out as much when hot. The reason using a thicker oil makes you burn less oil is it reduces the ammount that can get by the rings, VSS etc due to its higher viscosity.

[hmetro24]

Oh man, starter motor gonna go kaput. If i gonna drive in melbourne traffic its gonna pain in the ass.

[khanguskhan]

I was about to say exactly that, so much for looking after your car. Starter motor kaput, precious toda flywheel ring gear kaput.

[Egcivicduty]

I havnt turned my car off in years

also, I'm nobody, but here's what I think I've heard and seen.
the first is the winter rating, that is the cold viscosity, I think its measured at 0ºF or something (~-18ºC)
The second is the weight at operational temperature, which is generalized as ~100ºC
So a 0w30 and a 10w30 are the same thing at operational temperature.
Basically, most days in australia, the lower rating is irrelevant.

The best way to think about it, I guess, is that a 20w50 oil is a 20 weight oil that would only thin as much as a 50 weight oil would at 100ºC

The main reason i could think why 15w50 is too thick is that the polymers added to oil have a tendency to break apart in high temperature or high rpm applications, meaning the oil would break apart over time. Basically 15w50 turns into 15w25 or something.
Meaning you need to change the oil more frequently. Explaining why oil manufacturers would tell you its ok lol.
I'd also say that, as a generlization, the higher the spread between the cold weight and operation weight, the more viscocity index improvers added to the oil. Wide viscosity range oils, in general, are more prone to viscosity and thermal breakdown due to the high polymer content.
The polymers themselves dont do much in the way of actually lubricating the engine, so a lower spread would be better.
However, the heavier the base oil, the less Vi improvers required, so a 20w-50 would have less than a 10w40, even though they have the same spread.

I'm pretty sure that amsoil makes their 10w30 without any VI improvers.

and well, as stated. This is just my bleak understanding of the subject, and sorry if its hard to read, i wasnt really paying attention as i wrote it.

[Super-DA9]

I think some of those things are slightly different in synthetics, not too sure about how big a difference though. I think it's that synthetics are less likely to break down or something..

well I guess my question is, if you cannot use 15w-50, then are you just supposed to overhaul your engine when it starts to use too much of whichever 10w oil you are using? doesn't really make sense to me :/

[Bludger]

Super-DA9 knows best about his motor.

his choice to run 15w-50. I have no idea how many km's or what condition his motor is in, so he is best to judge what oil he uses.

We run 10w-60 in one of our b18's and 0w-40 in the dc2r.

[Bludger]

^^

that post was contradictory to my previous posts.

but my earlier replies were referring to a b18c where the owner made a blind statement that he runs 15w-50 "because it's safe"

[Egcivicduty]

indeed, I think I might go for 10-40 next time
and in regards to da9
its not the change from 10w to 15w that means its a heavier oil
the w stands for something like winter temperature, its measured at 0ºC, its only a grade for starting your engine
the second number is the relative grade of thickness at operating temperature.
so the thickness you are running at the moment is SAE 50, or something like that. You changed from 40-50 lol, i dunno how best to say any of this lol

[khanguskhan]

Thanks Bludger, it's only because I know that as a rough reason for my usage of 15w50, as I'm not as mechanically sound as the rest of you, and I have full trust in my mechanic, hence sorry if the way I spoke is misleading, but is it wrong for that to be agreed as safe even if my car is not burning oil at lower viscosities. 15-50 does not push the viscosity too far counting for Aus's weather?

[Super-DA9]

Super-DA9 knows best about his motor.

his choice to run 15w-50. I have no idea how many km's or what condition his motor is in, so he is best to judge what oil he uses.

We run 10w-60 in one of our b18's and 0w-40 in the dc2r.

Thanks buddy. my engine has 150,000km and has compression test results of 197-200 on all cylinders, however I'm fairly certain the valve guides have a bit of wear on them, which is the reason I use this over 10w-40.

indeed, I think I might go for 10-40 next time
and in regards to da9
its not the change from 10w to 15w that means its a heavier oil
the w stands for something like winter temperature, its measured at 0ºC, its only a grade for starting your engine
the second number is the relative grade of thickness at operating temperature.
so the thickness you are running at the moment is SAE 50, or something like that. You changed from 40-50 lol, i dunno how best to say any of this lol

yeah it seems this is right, my understanding from what I'd learned previously is that the "w" stood for "weight" meaning thickness, but it's good that I understand this properly now. thanks.

not that this would differ my choice of oil, as I've stated the reasons previously. so far I haven't had issues with 15w-50. maybe it would be really bad if we lived in a cold climate? :/

[Egcivicduty]

well, sure if it was Really cold, but the difference between 0w at -35ºC and 15w at -20ºC is only something like 30%
after 20 i think it gets thicker more rapidly
I remember something like that at least

[IV73CI]

what an epic debate going on right here!

well just to stirr up the convo,

im using Penrite 15/50 with a pint of extra virgin olive oil! :P

havent had any issues, was previously using Catrol Edge Sports 10/40 which was an awesome oil but costs me an arm & leg every 5k oil change intervals. (daily car).

My word of advise is, the correct oil to be used will be up to the below conditions;

- Klms of the engine
- Daily or weekend car
- Do you Vtaakk alot?
- Your location climate
- What type of fuel do u use?
- How often are your oil change intervals?
- What is your budget?

thats my 50cents yo!