My tC has about 73k on it and am thinking about running Mobil1 5w 30 synthetic oil. Do you think that's a good choice or stick with the 5w 20 toyota recommends?

 

you'll get better gas mileage with the 20 weight oil vs 30 since its a lighter viscosity. if you are just driving your car on the street stick with the 20 weight.

 

no do not go to a 5w-30 weight oil. The bearing clearances are tighter on your year 2007+ (and some 2006) and require a 5w-20, and i believe they were even saying 0w-20. Some will probably dispute me, but there was a TSB (technical service bulletin) from Toyota that said for 06+ 5w-20 should be used. Reason? They claim fuel economy but the fact that 5w-30 was being used on the 05 and those engines had crank bearing failure due to lack of lubrication most likely had something to do with it.

so if you want a synthetic you could easily get a 5w-20 synthetic and I just checked, Mobil 1 does come in a 5w-20 weight and a 0w-20, problem solved

 

Use what the oil cap says!

 

This. I have been following this rule, and have never had an engine failure on any of my car, even ones that have been known for a high rate a failure. I also keep the oil change intervals relatively low at around 3-4k even when using synthetic. I don't know that it's necessary, but I like to stick with what works.

 

5W-20: More engine wear, more gas mileage
5W-30: Less engine wear, less gas mileage

 

i always play it safe and go with the oem recomended oil, works for me. i do know that there is a tsb like sciontc_mich said, if i were you i would just stick with 5w-20.

 

4 quarts of Royal Purple 5w20 all day