Hi,
About to do an oil change and was wondering should I do conventional ,synthethic blend, or full synthethic? Car has 158000~ miles. I've searched but they were threads from a few years ago. Thanks

 

high km motors .and most camry engines . mineral oil is suggested

some recent exceptions where use of synthetic oil is required

local climate conditions and driving demands are factors in using different W ratings

online link
Toyota’s Stance on Synthetics
Synthetic Oil Good or Bad for Toyota Vehicle

 

It depends on a couple of things. What does Toyota recommended? Where do you live - high or low altitude, temps? What is the vehicle used for? How often do you change your fluids.

The link to the article by dirty hands is actually very informative and you should be able to deduce your answer thereof.

I barely drive 5k miles a year. I have taken to personally maintaining my Camry 97/178k miles. Since the oil is always clean when I do a 3k change, I have decided to switch to 5W30 synthetic from Wally.

If you start getting into nuances of oil first ErictheCarGuy says oil is oil, change it when you are supposed to car will be fine. Second I have read that in the US not all synthetic oils are actually synthetic. Once oils meet certain thresholds of some yada yada manufacturers are allowed to call them synthetic-you have to research this yourself. From these that's why I settled on 5W30 synthetic due to it's low cost. I don't care to spend a premium on oil after all I do a change every 3k and oil is oil. I will however try to do 5k on this and see. Further, there's a company whose name starts with Syno something and they make at least 3 brands of popular oils in the market. As you guessed it they are all priced differently of course. My pocket finds it silly to swear by the brands. My pocket want has loyalty to itself only and I am responsible for making $$ decisions that make $$ sense to me. People are different and so are the decisions they make over these same subjects.

Just before this past winter I put 20W40 and the oil was just too heavy. The car would vibrate more noticeably when it started in the morning, idle would be high until the engine warmed up. After 1k miles I switched to 5W30 (Toyota recommended) but wally synthetic and the car is back to normal.