I've purchased the car used about 8 months ago with about 58K miles, it's 2004 Toyota Solara V6 SE, everything appears to be fine however i still want to perform cleaning with Auto RX. I have no idea of what type of oil has been used before I purchased the car but i did 2 oil changes since I got it and used 5W30 Mobil 1 Full synthetic. Question is...I've heard it might not be the best idea when switching from synthetic to regular and back to synthetic, Since i'm on full synthetic now and planning on keeping using it, should i really use regular with Auto RX and then switch back to mobil 1 or whatever Synthetic? Is It safe? OR maybe instead of cleaning with regular oil i should only be doing maintenance by adding 4OZ of Auto RX to synthetic every time i do an oil change? Engine seems to be fine and i'm getting ~ 26MPG on the highway which i think is not bad for 3.3L V6 of my Solara. Thanks for advice but prefer to ask then screw something up and regret i haven't asked. Regards Greg
I don't think going from synthetic to regular would be a problem. Dino oils now day are pretty advanced. Auto-RX works best with dino oil. The problem with Mobil 1 is that it is a type IV synthetic. If you are that concerned about using a synthetic with Auto-RX you could switch to a type III synthetic like Valvoline or Pennzoil or some other brand of type III synthetic. Today for the first time I'm trying Wal-Mart's Supertech synthetic. Will be an interesting test. With 58K on it and since you don't know how the car was maintained I would do at least one complete clean and rinse before doing a maintenance dose. Don't forget to change the PCV valve too.
There's no liability of going from conventional to synthetic and back and forth. All things being equal ..oil is still oil.
The reason for the suggestion of Group III base stock oils is two fold. Some Group IV or Group V oils are complex and the time/mileage required for maximum effectiveness may be protracted. This has proven to not be a factor at the current mileage recommendation. Secondly, it presents a VERY expensive use of Auto-Rx to someone counting the costs compared to conventional oil. Now if you're someone who uses $7/quart oil for 3000 mile oil changes ..then there's no difference in cost. If you're someone who does 10,000 miles with $7/quart oil and now use it for a 3000 miles rinse phase ..that's a different story.
This would mainly apply to Euro-engines since they are about the only manufacturers that specify a limited list of oils (the list may be big - but in limited distribution) that are perhaps all expensive. Most domestic and Asian based engines specify conventional oil and synthetics are merely an option.
The school of thought is geared toward costs. Why waste 10,000-15,000 mile oil over 3000 miles when you don't have to?
