bubu

Hi all,
Would using 20w 50 synthetic motor oil be to much for a 99 rx300 with about 105,000 miles.
What do you guys think about that, some local parts guy said because of the high miles that I should look into a higher grade motor oil. I know that 5w 30 is the standard but because of the high mileage would you guys also think it would be a wiser decision. Please tell me the grade you guys on this forum use and also the brand. I was thinking Mobil 1 full synethetic.

Lexmex

I have used the following grades of Mobil 1: 5W-30, 10W-30, 5W-50, 15W-50.

For my hilly environment I would not recommend the 30 weights. The 15W-50 weight actually made me lose gas mileage. 5W-50 (available here in Mexico, not in U.S. to my knowledge) is the best of the oils for peformance and MPG.

If I were in the states, I would grab some 5W-40.

I was thinking about 0W-40 for a test.

Fern

I would continue to use the 5w30 motor oil recommended by Toyota and keep an eye on the level, ie: every 500 miles, although 100,000 miles is not considered high mileage.

Remember "the use of synthetic motor oil does not extend the oil change intervals" as per my owner's manual. More importantly just keep on top of the level and make sure it's always between the min and max level on the dipstick when engine is hot.

BOWTIE 3

A Japanese vehicle with over 100,000 miles could probably use the Mobil 1 10-30w. I think Japanese engines have closer mechanical tolerances. A typical domestic vehicle would be better off with the 15-50w Mobil 1. I had a GMC truck with over 200,000 miles and my wife's ' 89 T-Bird had about 150,000 miles [ always used Mobil 1 15-50w in both ] and never had an engine/transmission problem. The Mobil 1 10x30w will still give good fuel milage, lower engine temperatures, and provide superior protection. Any engine with over 100k needs a greater oil-cushion for longevity. When my wife's 2000 RX300 hits 60,000 miles later this year I'll be using Mobil 1 10x30w in it instead of the Valvoline 5-30w that the dealer uses when changing the oil/filter. We live in Virginia so the 10-30w will still flow readily in winter and give greater protection in the summer. If you were using the vehicle for towing I'd recommend the 15-50w right up front! The greatest period for wear is when starting the engine and the 10-30w covers that better than 5-30w.

Fern

Yes,
the greatest wear is on startup and therefore you want an oil which can reach the vital upper engine components as quickly as possible... This process is much easier achieved with a lower first number ie: 5W vs a higher number 10W.

The first number represents viscosity at colder temperatures, the second number represents viscosity at higher temperatures, hence the ideal weight oil would be 0W50, but good luck finding it. Try a Castrol 5w50 which seams to cover all bases...

At the end of the day what you don't want is an oil which is sitting in the oil pan until the engine has had a chance to heat it and circulate it around. Also, bear in mind the sludge factor with the Toyota 3.0 v6 engines.

I personally use 5w30 synthetic which seams to do great in all aspects of our Northern climate of -30 upto 40+ (celsius) or (-22F upto 104F) for those South of the border

Cheers,
Fern

Lexmex

The 5W-30 is great in Mexico if you are on level land. This is not the case in Mexico City and the RX would struggle much more going up hills on that grade than at a higher 40 or 50.

I was using Mobil 1 5W-50 but recently switched to 0W-40, which is giving me awesome results on MPG and performance.

Jeff92se

Oil note. While some might think a 0w 40 might be the best of both worlds, please remember. It takes ALOT of additives to get an only to act like a 0w when cold and a 40 when warm. So it's best to try to use viscosities that are as close as possible. Please read your owner's manual and use the recommended viscosities. And stop listening to the dude behind the parts counter. I highly doubt they know more than the Lexus engineers that designed your engine.

Lexmex

The parts guys happen to be Toyota engineers down here, who are actually switching customers over to 40 and 50 grades. If I were in the states, sea level, without mountains/hills to climb, I would gladly switch back to a 5W-30.

You have to see the place to understand why.