What synthetic oil is best for this car?

Depends on if you are currently using synthetic. If you have never used synthetic oil and have over 100,000 miles (or the vehicle was not maintained well), then you could lose oil pressure if you start now. Better to use a synthetic blend. Amsoil is often condidered the best, but can be twice the price of others and difficult to get. Mobil One is extremely good (O.E. in Porsche and Mercedes) but not as easy to find if you have your oil changed at shop. Pennzoil is rated very close to Mobile One, is a bit less in cost and widely available. High rating, cost and availability has me using Pennzoil.

mobil 1 is all i use. will never use pennzoil due to multiple bad experiences from family members with it.

Pennzoil says their Ultra full-synthetic has the best sludge-fighting formula, and nobody is calling them a liar. I switched my Sienna from Castrol regular to Ultra at about 210K. Now at 236K and it uses less than a quart between changes (5-6K miles.) No sign of any oil pressure drop using same viscosity as before (5W-30).

Valvolines maxlife synthetic blend high milage oil is a really good choice as well. It also comes in a full synthetic option. Ive seen this oil prove to extend life on engines up to 300k and beyond.

Will a Toyota dealer use good oil for my Avalon? Or should I use full synthetic oil versus a blend?

Bought a Toyota Avalon with 35k miles. What oil should I use?

ihave a4.o ford ranger2003, with176,500 miles, on mobile1 5W30 using mobil 1 oil filters (5 spd,4x4 with 4.10gears) change oil once a year. go max 10,000 miles on a change, now that I'm retired run around 7000 mile per yr. my 2014 Toyota Avalon gets changed once per year with mobil1 0W20& mobil1 oil filter, usually just a few miles over10,000 per yr. now is approaching 50,000 miles. neither vehicle leaks or uses oil Ranger still makes20mpg and Avalon does 27-28 mpg puts around wife car. drove to Dallas,tx over thanks giving from south west Missouri, averaged 35plus mpg running speed limits. using tier 1 89 octane fuel by MFA(farm fuel and shell 89 octane on return trip use synthetic oil, keep it clean with best filter you can afford.run tires at 40psi. my2014 f150 crewcab 4X4, eco boost, using 5W30 mobil1 with mobil1 filter with a catch can oil vapor recovery, using tier1 89 octane MFA gasoline, tires at 45psi,front, 35 psi rear best has made 18mpg on highway trips with normal rd town between 14and15 mpg

I had a 2003 toyota avolon with 290,000 I did nothing to this car but put the cheap oil in it Regular conventional oil changes at valvoline and I would go 10,000 + in between changes never had any issues. I know it’s not a good idea to do that but that’s just what I did. I sold the car 5 years ago miles 290,000 and I still see the lady driving it around ran into her the other day and she hasn’t change the oil since I’ve given it to them. What a well made car. Only thing I ever had was an O2 sensor and front brakes a few times. Crazy good