colenzae

Have an rx with 157,000 miles. Want to get 250k out of the vehicle. Have heard about sludge problems with this engine and that synthetics can prevent this.
What is everyones experience been with synthetics?
I just changed out the transfer case fluid on my awd rx with mobil 1 75w/90w. and I plan to do the same to the rear differential.
What about my engine and trans? What are the advantages/dissadvantages to switching to all synthetic (or a blend if that would be better) for the engine and tranny?? Which are the "best" synthetics or blends on the market??
Is there already a faq for this topic???

GS4_Fiend

iTrader: (22)

AMSOIL is the BEST!

Lexmex

Amsoil is good and you can't go wrong there, but the price and availability are the things that really knock them. I do swear by their Amsoil ATF.

There's no real FAQ on this though I do mention some things on my car domain site on page 9, http://www.cardomain.com/ride/2215309/9

The answers you may want to get are from people who have switched, primarily in engine oil from conventional to synthetic, but I can only speak positively of changing from Type IV ATF to Amsoil ATF.

sktn77a

iTrader: (2)

If it's going to sludge, it's got it already. Take the valve cover off and take a look. The only think that will prevent sludge is frequent oil changes. If you're looking to keep your car for another 100,000 miles, use a good engine cleaner treatment and then change the oil every 5k.

colenzae

I have never used an engine cleaner but I have changed my oil & filter together no more than every 6k.
BTW is Amsoil 100% synthetic a blend or conventional??

sktn77a

iTrader: (2)

Then you should have nothing to worry about

Although this is a highly debated topic, I found that switching to synthetic engine oil caused leaks in two of my older cars cars (~90,000-100,000 miles) . Switching back to dino oil stopped the leaks. Go figure!

AlexusAnja

Someone already said it, if it's going to sludge, it would have already. If you do your changes often and it hasn't been a problem, then don't switch now. I've read and heard plenty where going synth. in higher mileage vehicles is actually detrimental because the synth. flows better and might cause leaks where conventional oil won't flow through. I would leave it be. You'll get to 250K fine, as long as transmission holds out.

colenzae

So then the same holds true for the transmission; don't switch to synthetic now, just be diligent with drain & refill??

trhs75

We got my daughter's 99 with 115K miles on it, and I doubt synthetic oil was used before. I started using Mobil 1 as I use on all our vehicles, and so far the RX hasn't appeared to use or leak a drop with 5K changes. As sktn77a pointed out, switch back to dino if leaks begin.

colenzae

Someone told me the same thing. They went with a synthetic and the engine started leaking. They went with a blend and no more leaks. So I think I'm leaning toward a blend.
Anyone have experiences with blends???

jimmouse

mine 01 awd has ~220k on it. mobile1 syn with mobile filter every 5k or occacionally 7.5k. It looks like 250k is not far away.

AlexusAnja

You had synthetic from the start (or close to new) and always had it, or you started later on? I've had synthetic on all my vehicles from "start" (all below 40K or new) and no leaking problems either. I think the problem is when you start on an older engine, where the dyno oil may have gell'd a little and is actually clogging up minute holes that would otherwise leak with synthetic. So, when you switch to synthetic with the better flow and viscosity, it starts to leak.

splacek007

Now that it's been a few months...what is your experience w/ Mobil 1 75W-90 synthetic gear oil??? I just purchased a few quarts and intend to do exactly what you indicated in your OP (transfer case/rear diff.). Good results?

colenzae

I have to say that things feel smoother. I went with Mobil 1 for the transfer case and a synthetic blend for the engine. Sticking with the Toyota Type 4 or the Castrol equivalent for the tranny.
So I can recommend the fluids I've used so far. Hope that helps.

bob2200

My feeling is that changing oil regularly (e.g., 5-6,000 mi) isn't good enough if you are taking it to a cheapo place like JiffyLube. I don't know where the threshold is for adequate oil/filter quality but I think JiffyLube is under the line.

I change my oil every 3-4,000 miles using a Toyota/Lexus filter and typically Castrol GTX conventional oil. I usually purchase the Castrol GTX in 5-quart containers at Walmart.