DaveJ

I'm thinking of changing to Mobil 1 synthetic oil on my wife's 90K miles '00 RX300. Do you use synthetic or regular oil? Might there be a problem switching to synthetic after so many miles?

Lexmex

You will have no problem going to synthetic.

Stick with Mobil 1 5W-30 the first time out...but you may find later that given the number of miles you have...you might want to try a different grade.

I have experimented with several grades of Mobil 1 (5W-30, 5W-50, 10W-30, 15W-50 and 0W-40). I am sticking to Mobil 1 0W-40 and I also use the 6-cylinder version of Restore to help compression.

I just passed 100K tonight

Fern

purchased my truck with 48500 miles and moved to Castrol Synthetic 5w30 and have used nothing else since. Altho I did apply engine flush prior to switchover.

When going from conventional to synthetic you will notice the next few oil changes are darker than normal... this is ok, since synthetic contains detergents which clean the inside of the engine as its lubricating...

My engine now at 76000 miles and is cleaner between oil changes (every 3700 miles) than it was when I got the truck.

Winters up here in Canada, Eh, can get pretty cold and no valve knock on startup. Also less possibility of sludge buildup which these engines have reputation for and the fact that I got a heck of a deal on 6 cases of Castol Sythetic. I change my own oil with genuine Toy filter for less than dealer charges with crappy oil.

Dealer will tell you its not necessary, its also not necessary to do other stuff which those who care do, ie: rustproof, etc....

xfirechief

Strongly suggest not changing to synthetic oil at 90K. Vehicle has way too many miles on it. Synthetic oils should be started before 10K. At 90K there may be what is called false seals in the engine. That means that varnish & sludge buildup keep the oil from getting past the seals & rings. If u put in a synthetic oil they will clean that engine right up & get rid of those "false seals" and watch it use oil. Then people will blame that darn synthetic oil when it was just doing what it was suppose to, keep the engine clean.

I have used AMSOIL in all my vehicles since 1980 and never had any oil issues but I started using it before 7K.

Just my 2 cents but I know from past experience that is what can happen. I have also sold AMSOIL since 1982 so that is what I have told my customers & I never have had a engine problem or failure.

katzjamr

I think at the very least you should be able to change to a synthetic blend. Castrol synthetic blend (part dino oil and synthetic) is used on the 400h at the dealers. The beauty of this product is since it is part regular oil it is never a problem to change into and you get the benefits of the synthetic oil in the product. It is not a full synthetic like you would use for 15K between changes however i feel that it gives you superior protection. I use it in all my vehicles. Quaker State also makes this product under the name 4x4 oil.

Fern

xfirechief,

this topic has been discussed on numerous forums and I don't quite understand your point:

- so using synthetic while the car has 10k or less is o.k.
- using synthetic after that is not...

are you saying that conventional (dino) oil is actually ruining the seals from 10k onward...?

Yes, the dino oil does develope sludge and that sludge will collect in the engine specifically where the seals are, and yes older cars may react differently to the "seal-swellers" found in most modern synthetic oil. Most newer cars already have tolerances built into the seals to account for the detergents in oil and fuel.

at the end of the day, I would like to know that over the course of its life (in my hands anyway) my car has had the best it could have.

All said, Synthetic is no substitute for an engine which has not been maintained by it's previous owner...

One last point, when switching to synthetic on higher mileage vehicle, be sure to check the oil level more frequently and keep topped off , as the car might be more prone to oil consumption due to WEAR over the course of it's life with DINO OIL.

Just my $.02

Lexmex

I agree 100% Fern. I wanted to add that even on oils such as Mobil 1 15W50 they state this is for higher mileage engines.

xfirechief

I hope u read my 1st post as no where do I say don't use synthetic oil after 10K.

I strongly suggest using it by 10K & then keep using it for the life of your vehicle. When a engine has more then 10K on it & the oil has not been changed yet or maybe only 1 time u should run a mild engine flush though it to get any varnish or early sludge(dirt) out of it.

And no dino oil does not ruin seals after 10K but dino oil requires changes in the area of 3 to 5 K and if u do not do this the engine parts will wear faster as dino oils are not built for higher mileage drain periods. I have seen people never change oil & only add as needed & would never recommend synthetic oil to them after say 15 - 20K unless they flush out the engine. And then watch it closely.

Again, the question was should this person go to SYNTHETIC OIL after 90K, I stick by my recommendation and say NO. At 90K it is too late. Use synthetics on your next vehicle.

So, yes if u want to switch over to synthetic on a high mileage engine don't blame the synthetic if u start using oil as u won't be happy.

I do agree with Fern, synthetic is no cureall for a poorly maintained engine.

mmahamm

The dealer just replaced the Rear Main Seal on my 02 RX300, at 43,000 miles. We bought it CPO in June, with 32K miles. The dealer changed the oil at 37K, and I changed it at 42K, both times with conventional oil.

Based on all I have read, my belief is that you can change to synthetic any time. The dealer told my wife that the cause could have been someone using "the wrong oil." When someone says something like that, I usually bristle, because I know I use the right oil, and I know how to change it. But I personally have only changed the oil once on this vehicle, with a high quality conventional oil. Possibly the previous owner did not maintain it properly, and I will have to review that (I got a print-out of maintenance records when I bought it)

But they apparently said that you should not use synthetic in these engines. I think they are not looking hard enough for a real cause.

What do you think?

xfirechief

I STICK BY WHAT I SAID
The dealer does not want u to use SYNTHETIC because for one, they may not sell it & two you won't be back every 3 - 5 K for that oil change.

Now if your rear main was leaking at 43K it may have just plan been a bad seal. Or, if the previous owner didn't change the oil & filter every 5K( maybe never) & u changed it 2 times in 5K you may have washed away the "false seal" & now u have a leaking seal.

supra_trd

iTrader: (3)

100% senthetic but change the oil as recommened by factory manual of 3000 miles.

Lex2000TL

I disagree with the statement that you cannot use synthetic oil after certain mileage. Please do Internet search for this topic, that has been beaten to death already. Check Acurazine.com forum and you will find tons of information with reference to specific websites. It’s OK to switch to synthetic at any time/mileage with no harm. Synthetic oil does have better life and cleansing ability. It is also “thinner”. As result, some engines that have not been leaking oil might spring small leak through gasket(s). The benefit of using synthetic oil is longer oil life in the engine due to better heat resistance, better and faster lubrication in cold start (the worth possible condition), and better washing ability. The latter helps to maintain clean oil passages in the engine. I switched to synthetic in my wifes RX300 at 35K miles, and in my Acura at 60K with no harm done so far (couple of years of use). I change it every 8-10K miles. I have the oil tested by Blackstone Labs after 8K miles, and test results came with conclusion that the oil shad about 7K miles life left.
Regarding varnish working as seal: if your engine piston and rings are worn, no warmish will ever hold the seal.

mmahamm

Manual recommends 5,000 miles. 3,000 miles is what Jiffy Lube recommends so you pay them more money. The engine will not last any longer but you will have less money.

Fern

MY
lexus manual states in maintenance section oil change every 6000 km or (3700 miles) and also states the use of synthetic oil does not extend the oil change interval...

I don't want to beat this dead dog any further but,
if you use synthetic oil and go the 12000-15000 km intervals that some dealers of other car manufacturer are doing, then it's actually cheaper, ie

*BMW charges $100/ oil change and the average interval is 14000 km, which factors out to about 3 oil changes (with conventional oil) or an equivalent cost of $33/oil change... not bad...

*This is just to play devil's advocate to those saying synthetic oil changes cost more, which they don't and btw they are much more environmentally friendly (less frequent disposal)

xfirechief

Finally, someone posted what I wanted to get across about the use of SYNTHETIC OIL.
Basically it is less expensive to use synthetic oil do to the fact you extend drain intervals.

As for engines with higher mileage, yes, you can put in synthetic but you should & must know the history of the maintenance as far as frequancy of oil changes. If done 3 to 5 K inc. the filter, there should be no problem but if not be ready for problems & don't blame the SYNTHETIC OIL.

AMSOIL has just introduced a new oil filter that has the capability to go 1 year or 25K as does their oil under normal driving conditions, and 15K under hard driving conditions. That can save you from 3 to 5 oil changes in one year plus the time at takes to get it done. Now add up the cost savings and what should you use? Not to mention less wear on the engine itself & increased mileage because of less friction.