I have been using Mobil 1, 5-30wt full syn. every 5,000 miles. I saw that the same full syn. oil is also in the 15,000 mile extended run version in the brown bottle. The price is only about only about 70 cents between the two. I figure i would run it for about 8,000 miles instead of 5. I don`t think i would leave it in for the full 15,000. I still would be saving money. Is it that much better oil? What makes it diff.

 

I've used the extended interval oil in two of my cars, a 2000 Lincoln LS and 1996 Ranger P/U changing the oil once a year. These cars each go about 6-8K miles a years. I'd actually feel comfortable using regular Mobil 1 in the same manner. My wife drives our RX and I change that every 6-8K miles using regular Mobil 1. She probably puts 10-12K miles a year on her car. I feel in modern cars using modern oils and filters frequent oil changes are a waste of $. You'll likely find not everyone shares this belief...

I don't know how the two oils differ, may just be the price and bottle!!

 

What year is your Rx? If its a "newer: car...2005 and up I would have no problem with OCI of 15K.....The older models like mine(2001) had the sludge issues and IMHO i would not do long intervals

Good Luck!

 

we've had two. The one I was referring to was a 2001 RX with FWD which had 109k miles when we passed it along to our daughter. My wife currently has a 2007 RX. We'll stick with the suggested guidelines on that while it's under warranty. I'm well aware of the sludge issue. I doubt you'll find many Toyota motors that failed, with sludge issues, while using synthetic oils that were changed fairly regularly. I think every 6-8K miles with Mobil 1 is "fairly regular".

Either that or we've been lucky

 

Does anyone know why the older models had the sludge problem more than the newer ones? Was it the motor or inattention to it? Seems that 5k miles is ok for an oil ch. with almost any engine. True?

 

I think it was something to do with the oil return holes in the heads were too small and people were running dino and not changing soon enough. If I remember right the heads run very cool which when combined with the oil puddling in the heads made for sludge.

 

I buy the Extended Performance 5qt jugs from Walmart but OCI is 7500. Maybe next time I should check my oil at 7k miles to see how bad it is and change the interval? Am at 165k now