If car already consume engine oil , we should thicker engine oil , right ? But , i feel that when i use catsrol 20w50 , the car is sluggish , and the fc is bad . Anyone can suggest engine oil give better response and fc for my old car ? my car is old saga 2004.

my car 10 years already..currently using castrol magnatec 10w-40...

Buy those 15W40 engine oils in 5L/6L/7L packing. Top up when necessary.
For example, Rimula R4X (5L), BHP Trans Super (7L), Mobil Delvac MX (5L) etc.

Engine Makan minyak no need top overhaul.
In Hokies just change the ba kah ni. I Duno wtf is that but it's something that seal the piston thing.

If kul every workshop sure say need top overhaul

ba kah ?

will it hurt the engine by using slghtly thinner oil such as 15w40?

rimula is shell ? i only heard about shell helix

rimula r4x is heavy duty EO...for diesel engine..but i use it on my motorcycle..

petrol engine can use ?

also can...my lc135 can use it..mesti boleh..

Try HDEO 15W40 > PCMO 15W40 > 10W40.

Helix HX7 10W40

You should be looking into the source of that excessive burnt lubricant, otherwise you might later have other issues like wet/prematurely worn plugs, clogged PCV, sludge clogged cylinder head, excessive blow by, dirty carburetor/engine bays etc. Having thicker lubricant is only a temporary solution if its not too bad, and one of the consequences of using thicker oil (especially on higher worn engines) is poorer performance, followed by poor fc as you have encountered.

FYI 2004 is not that old. My older 2000 Corolla is still running on 15w40 lube.

Agreed.

My crv year 1996 with BOT still uses 5w30 full syn. oil. Old doesn't mean anything if u take good care of your car and follow the maintenance schedule on oil change. However once there is indication on oil leaks or engine oil burning, do send it for fixing. Cars burning engine oil are damn annoying and coupled with damn selfish drivers by emitting the oily fume all over others and on the road.

iswara engine original spec is to use xW40 engine oil, so no hurt at all.
Rimula is name of heavy duty engine oil of Shell.

Agreed.
My 1985 Corolla XL also using 15W40, Kendall Super-D XA HDEO.

I saw my another old saga 1991 engine bad stated 20w50.... Perhaps 2004 engine is different?

Ba kah ni is valve stem seal la, that consider top overhaul la.

So, 15w40 is OK for my car although there is leaking?

I still dont understand how to choose engine oil...

eg 10w30 vs 10w40

theoretically 10w40 means the oil will stay in better condition compared to 10w30 when the engine is running hot like long distance journey right?
but if city drive its its better to use 10w30 because its less thick so engine need less effort to move?