Goodday to all. I was suppose to post an answer this morning but i was in a bit of hurry and had a bad connection. I will try to answer your question in a Q&A type.
1. Engine oils are not the same. There are oils that can be used for Diesel ONLY, for Gasoline ONLY and there are some rated for both.
2. How will you know what oil is for your engine? there is an API rating for oil. If an oil is "S" rated this means the oil is meant for Spark Ignition engine or Gasoline engine. If an oil is "C" rated, its meant for compression combustion engine or Diesel engine. Look at your manual what kind of oil rating is required for your engine. For gasoline there are SM, SJ, and SL rating. For diesel there are CJ-4, CI-4 Plus, CI-4, CH-4, CG-4, CF-2, and CF. All others are obsolete. You should ONLY use oil with the same rating for your engine.
3. Why are oils different for gasoline and diesel? Compression combustion engine or Diesel engine has higher compression ratio. Meaning the engine experience higher operating temperature. Thats why diesel engine needs special oil. The viscosity rating of diesel oils starts from 40 eg. 5W-40, 10-40, 0W-40, SAE 40. For gasoline engine they can use oils with viscosity rating of 30 eg. 5W-30. This is because gasoline engine is cooler than diesel engine. A diesel engine oil will not be able to lubricate properly at thinner viscosity. A diesel oil has a higher anti acid additive (KOH). For gasoline anti acid is 7-10 mgKOH/gm oil. For diesel its 11-15 mg KOH/gm oil. this is because the higher the operating temperature the more prone to corrosion since oil degrades faster when hot. Diesel oil has higher detergent additive due to greater soot formation.
Note: there are oils that CAN be used BOTH for gasoline and diesel. BUT i would suggest that you use oils that are really suited for GASOLINE ONLY or DIESEL ONLY since the additives are really within the standard value. If your engine is TURBO equipped, use oils that is Suited for Turbocharged engine. Dont use those that say, CAN ALSO BE USED for turbocharged engine, hilaw ang statement na yun. Ako i use Mobil 1 Delvac that is really for diesel engine with turbo. Dati i use cAStrol CRB turbo pero the engine vibrates stronger. The turbo spins 6 to 10x faster than the crankshaft thats why the sheer stress is greater so if you use a non turbo rated oil, the oil will get too hot and dry up causing turbo failure.
4. Ano ba yung meaning ng 5W-40. Bat meron naman SAE 40?? Pag MONOGRADE oil ang rating SAE 40 meaning ang viscosity rating is 40. Pag multi grade oil me wider ang viscosity range eg. 5W-40 meaning pwede sya for for winter (W) at temperature -30*C still liquid pa sya. nilalagay ng VI yung oil (VI- viscosity improvers) to be able to maintain its luquid state even below freezing point. This is designed for cold countries. satin di naman applicable. Kung di naman turbo engine mo ok na yung SAE 40 mas mura pero kailangan pasok sa diesel rating eg. CJ-4. Dahil yung VI eh nakakasama pa. Pag umiinit kasi yung oil, yung VI ang unang nasisira, pag nag breakdown yung oil yung VI ang nagiging sludge. kaya the closer the viscosity range the lesser the VI hence the lesser the sludge formation.
Hope i answered all your questions.
Yang polo depende kung suited sa rating ng oil mo... pero kung ako tatanungin mo before you use any oil, unang tanong agad, SINO GUMAWA?? mAdaming backyard oil blenders. Ingat lang mga sirs. Also look at the viscosity range. 0W-50. This means it can be used from -35*C all the way to viscostity rating 50. Napaka wide ng viscosity range. Ano uli sabi ko?? the wider the viscosity range, the greater the VI the greater sludge formation. Tapos yung API rating nya CI-4, SL, pang gasoline na pang diesel engine pa. Avoid oils like that if possible.
Sa mga shell brands?? please look at your manual what is the rating ng oil pwede tapos pag bumili ka tingin ka sa likod na label hanapin mo yung meron sya na ganun rating.
Ok ayos na ha?? Wag na maguluhan hehehe.