Why is the dealership against me using 5w20 synthetic?

[CXTKRS1]

I stopped by the local Toyota dealer to ask the service manager if my warranty would be intact if a ran 5w20 synthetic instead of the 0w20 recommended in the manual. He told me no that only 5w20 dino oil can used and if I switched to synthetic I would have to use 0w20. I really cannot find a reason as to why I must use 0w20 especially considering the climate I live in. :boxed:

[TexXBox]

I would say that if the engine can run 5w20 dino oil that there is no way it couldn't run 5w20 synthetic. The only difference between the oils is the chemistry used to create them. The viscosity indexes are the same.

With the advent of synthetics the oil companies have been able to create a "0" weight oil that is impossible to obtain with conventional oil. If an engine is designed for "0" weight oil then the bearing clearances might be small enough that an "over weight" oil like a 5w might be too thick to adequately lubricate the engine during start up and for the first few minutes of running no matter what the temperature.

Since our engines have been designed and run on 5w up until the '10 model year I can't imagine that using it now would make a difference. The switch to 0w specification is probably to provide a little bit of leeway to aid in the switch to the longer oil change intervals introduced for 2010. As the oil ages and sludges up over the longer interval it ends up about the same as the old 5w did during its life.

If you do use the 5w I would definitely change it at the old interval or sooner rather than the new extended one.

[XDevolution]

I use 5w-20 full synthetic and i have gotten nothin short of spectacular performance, the car responds alot better and feels so much smoother as i cruise. throttle response and acceleration improved a bit. before it felt as if the car was dragging when i used a synthetic blend, i think using full synthetic was a wise choice.

[iperez85]

using 5w-20 dino, 5w-20 synthetic, 0w-20 synthetic, its all good for the engine and if you read your owners manual carefully, you can use either/or.