Is it okay to drill holes in my catalytic converter?
Your “friend” is an idiot.A cat will pose no significant restriction. There is no gain in performance.If you drill holes into it you fool the oxygen sensors into thinking the mixture is lean. That will tell the ECU to command more fuel and it will skew fuel trims. You will get a “check engine light” and pay $ 80.00 in my shop just for the knowledge that you are an idiot.You will come to my shop after having been to Autozone , where they scanned your car for free and sold you an oxygen sensor you didn’t need in the first place.Why are you doing this? Why do you want your car to sound louder?Loud cars are owned by idiots.If you want to get laid then read books. Become literate . Go to the library and make eye contact with intelligent dames. Driving around in the neighborhood with a hole in the muffler ain’t gonna get you laid.
Is it okay if I use engine oil rated 20W50 instead of the 5W30 oil stated in the vehicle manual since I live in a tropical location?
No, your engine is designed to pump the oil recommended at full working temperature which is around 100 deg C. The fact that your air temperature is around perhaps 30 deg C is irrelevent.Any 50w oil, whether 5w-50, 10w-50 or 20w-50 will be too thick at 100 deg C and will fail to flow as fast as the engine maker intends so will not carry heat away as well as the intended 30w.Furthermore, at start-up, the 15w-50 will be at least 10 times thicker than rthe 5w-30 and will pump so slowly you’ll get a high rate of engine wear even before the oil gets to temp.There’s a reason engines only lasted for at best 100,000 miles in the ‘70’s and it was because they used 20w-50, the 20w part causing extremely high wear before the oil was hot.Most if not all 5w-30’s are fully synthetic which can handle much higher temps than any mineral oil so high ambient air temps are simply not an issue. The 15 degree difference between the 15 deg C on a cold day in the UK, and the 30 deg C you might enjoy is literally irrelevant compared to the 300+ deg C the oil is good to.
What does it mean when the engine is seized?
Engine seizure is normally the result of a failure of the lubrication system. It is often where a piston has friction welded itself to the cylinder bore. Sometimes it will be the big end bearing , the main bearings or the small end bearing. The net result is the same, though. The engine cannot be rotated. If you are very lucky, and the siezure is only slight, then the engine may free up again when it cools down. But damage will still have been done. Until water cooling and special oils were developed, racing two stroke engines were notorious for piston siezures.