What is rule for changing oil. I have 2 Lexus and sole driver. Question I only drive each car 6 months, RX in winter and ES in summer. Is it necessary to change oil if one car sets in garage for 6 months. Book says either 5,000 miles or 6 months. Suggestions please............

 

I go by mileage but I'm sure others have their own opinions. Be sure to use some fuel stabilizer or injector cleaner if your car sits too long to prevent gum and varnish in the injectors. I'd also use a trickle charger so your battery doesn't go dead.

 

Go by the owner's manual....unless you have more knowledge and experience than the engineers that wrote those schedules.

 

Problem is when a car doesn't get driven often, or on longer trips, moisture and unburnt fuel will accumulate in the motor.

If the oil was changed, then the car sits for 6 months, then its driven, just fine to let it go a year. Same as if its driven 6 months (less than 5000 miles), and then it sits for another 6 months. No biggie. Its saying if you drive infrequently but regularly, every 5k / 6 months. If 6 months of it is just sitting, no biggie.

 

Would this rule of thumb apply to fully synthetic oil or would it get pushed out longer?

 

The service intervals don't change per the manufacturer, but many oil companies claim you can go longer.