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 Using lower-viscosity engine-oil in old engine, How to prevent white/blue smoke issue?

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xxboxx
post Feb 4 2012, 03:02 AM

The mind is for having ideas, not holding them
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From: J@Y B33


QUOTE(kEITh_22b @ Feb 1 2012, 03:09 AM)
Hi guys,
An engine-oil change will be due for my 20 year old car engine soon;

Currently, this old engine is using the Shell 15W - 40 Mineral engine-oil - (without having any white/blue smoke problems at all).

But for this coming engine-oil change, I am planning to go for the Shell 10W - 40 Semi-Synthetic engine-oil; which has a lower-viscosity - (it will be a thinner engine-oil grade for this old engine).

I would like to put a lower-viscosity (thinner-grade) engine-oil into this old engine to improve it's fuel-efficiency & horsepower. (Correct me if I'm wrong.)

However, I do not want to see any white/blue smoke issues pouring out from this engine after filling it with the lower-viscosity engine-oil...

So the thing is, what (the name of the components/parts) can I tell the mechanic to check/change inside this old engine - (that will minimize or eliminate the possibility of the white/blue smoke issue from happening?)
Your information/advice will be highly appreciated.
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bro, you normally rev not even past 3k rpm, of coz cannot see any white smoke. You should try rev till 5k or 6k and see if really there is no white smoke. Also check your exhaust muffler tip to see is it oily or totally dry with only the black carbon.

QUOTE(kEITh_22b @ Feb 2 2012, 12:18 AM)
I reckon it is also not a good idea to let the mechanic open up this old engine to check here & there... I worried later need to end up doing a full-overhaul. ohmy.gif (Because now the engine is still running perfectly fine. nod.gif )
Oh my, I've never been checking my engine oil level at all... (I'll keep it in mind to occasionally check from now on...)
So far, this old engine does not have any oil leaking problems at all, but I reckon I should start the practice of checking the oil level from time to time...

Will the mechanic have to open up the whole engine to check the "oil seal & gasket"? (Maybe this two components is something I can tell the mechanic to check/replace if necessary...)
But the issue with the 10W - 30 engine-oil grade is that it won't offer so much protection (as the 10W - 40 grade) when the engine (and the weather) gets hotter isn't it? (It will break down faster under higher-temperature & possibly cause sludge build-up isn't it?) unsure.gif
But how come the mechanic (last time) advice me not to go down to 5W - 40 (a thinner oil grade) from my current 15W - 40 (a thicker oil grade), because he told me that the engine oil will start leaking (because it will be too "thin" for my old engine to handle...) unsure.gif

Hence, I don't think the 10W - 40 engine-oil is having the "same" viscosity-level as the 15W - 40 engine-oil (which will naturally still be the thicker oil)...

Correct me if I got it wrong...
Again, I still think that the 10W - 40 engine-oil grade is "thinner" than the 15W - 40 grade. (However, both engine-oil grades will be having the same "resilience-level" at high-temperatures.)

Again, I am worried that the 10W - 30 engine-oil grade will not be as good as the 10W - 40 engine-oil grade in protecting my engine at higher-temperatures (hotter weather & longer idling in traffic-jams etc... as such.) Because it will break down faster than the 10W - 40 grade engine-oil... (I think...) hmm.gif

Now assuming there is a 10W - 60 engine-oil grade, it's viscosity-level will still be exactly the same as the 10W - 40 engine-oil grade, but the 10W - 60 engine-oil grade will be having a significantly higher/better "resilience-level" at higher-temperatures (it will take longer for it to break-down under higher-temperatures - the oil will have a significantly better chance to last longer).

Correct me if I'm wrong. (I hope I am not confused...)

Thanks a lot to you guys BTW.
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10w40 does not have the same viscosity with 15w40, "only when the oil is still not heated up". Once it is heated up to operating temperature, both have the same viscosity. So the foreman that never learn about oil will change viscosity when it is heated up of coz will say the oil is lighter/thicker,they just based it on the oil that came out from the bottle.

Your engine is quite old,some more I believe it's been many years since it is overhauled? There might be places that have gap / hole but it is patched by the sludge from all this time using mineral oil. Changing to semi synthetic and its cleaning agents might cleaned up these sludge and resulted in the oil sipping out from these gap / hole. Unless you prepare to do top overhaul or even full overhaul if this problem do arise, it is not recommended to change to semi or fully synthetic.

On the issue of using lower viscosity oil, ie. xW30. Your engine maybe is designed to run on higher engine temperature, changing to lower viscosity might result in the oil vaporize and also premature shearing, which make the viscosity even lower. And then there the risk of the oil unable to protect the engine efficiently due to lower viscosity. 20 years old engine, I'm sure the recommended viscosity is xW50, you can use xW40 since you also not always high revving the engine, but going for xW30 just seems too low.

 

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