Synthetic Fluid For Transmission And Rear End Differential

[mnesbit]

It is time to change my tranny and rear end differential for my '95 LS400.

IS there a synthetic fluid for this and does anybody know if it is worth doing?

Thanks, Mike

[gabep]

http://www.amsoil.com/

[jcrome04]

amsoil or mobil1 full synth

tranny: ONLY USE OEM TOYOTA TYPE-IV

[Johnsoils]

AMSOIL universal ATF will work just fine in the Lexus transmissions. It meets the specs for most all transmissions except for Ford Type F and the new CVT transmissions. I just did a pan service and flush for a customer and she said the transmission shifts better than ever before. She had 82,000 without a service. The old fluid looked like chocolate milk.

[TA in KC]

It is difficult for me to understand why people pay lots of extra money for Amsoil-branded fluids. Can they really be that much better than Toyota OEM fluids, or other synthetic brands?

I have not done lots of research on the subject, but from my experience on this board, and others, I have been unable to find any evidence from credible sources that proves Amsoil is any better than regular synthetic oils.

My 1992 LS, approaching 150,000 miles, and a friend's 1994 LS with over 300,000 have been, and are still doing fine with Valvoline synthetic blend oil and Toyota OEM transmission fluid, changed at recommended intervals.

I personally consider Amsoil and other high-priced synthetic fluids to be a huge waste of money.

[AZ Mike]

It would appear that Amsoil is a good oil. Significantly better than Mobil 1 or other synthetics? Arguable. Ask any Amsoil devotees, and they will send you charts showing Amsoil to be one of the better oils in various technical tests. What do these charts mean to the actual performance of your car or mine? Well, maybe you can wipe up oil drips from your oil change with them. ;) The only sure way I know of to test the different oils in your own vehicle is to get used oil analyses and make the comparisons. However, this runs $22 per UOA from Blackstone, plus postage. The other alternative is to use a quality oil at the intervals recommended in your owner's manual; a less scientific, but less burdensome on the wallet option.

Unless you are using extended oil change intervals, I am not convinced that the use of synthetic oils makes sense. The one proven benefit of synthetic oils is that they do not break down as quickly as conventional oil, therefore serving the oil's purpose for a greater number of miles. Other benefits are arguable.

With respect to transmission fluid, I am in agreement with jcrome04: Toyota Type IV ATM fluid only. In my experience, transmissions are the one component that appears to be most sensitive to the fluid used. For example, there are many who change up fluids in the crankcase and differentials with no ill effect. However, there are many instances where people using different fluids (than called for in owners manual) in the tranny leads to all sorts of problems. For transmissions, my personal choice is to strictly stick to OEM fluid. This may be overkill on my part, but I would rather be safe than sorry.

[TheeSlowPoke]

It would appear that Amsoil is a good oil. Significantly better than Mobil 1 or other synthetics? Arguable. Ask any Amsoil devotees, and they will send you charts showing Amsoil to be one of the better oils in various technical tests. What do these charts mean to the actual performance of your car or mine? Well, maybe you can wipe up oil drips from your oil change with them. ;) The only sure way I know of to test the different oils in your own vehicle is to get used oil analyses and make the comparisons. However, this runs $22 per UOA from Blackstone, plus postage. The other alternative is to use a quality oil at the intervals recommended in your owner's manual; a less scientific, but less burdensome on the wallet option.

Unless you are using extended oil change intervals, I am not convinced that the use of synthetic oils makes sense. The one proven benefit of synthetic oils is that they do not break down as quickly as conventional oil, therefore serving the oil's purpose for a greater number of miles. Other benefits are arguable.

With respect to transmission fluid, I am in agreement with jcrome04: Toyota Type IV ATM fluid only. In my experience, transmissions are the one component that appears to be most sensitive to the fluid used. For example, there are many who change up fluids in the crankcase and differentials with no ill effect. However, there are many instances where people using different fluids (than called for in owners manual) in the tranny leads to all sorts of problems. For transmissions, my personal choice is to strictly stick to OEM fluid. This may be overkill on my part, but I would rather be safe than sorry.

I haven't verified it yet, but my understanding is that there is an added benefit to using synthetic oil in cold climates. The synthetic oils don't "gell" up, i.e. get real thick, when cold. Is there any truth to this? No matter what car I have had where I usedconventional oil, cold starts seem to be tough on them. I say this because of how hard, and slow, they turn over in the extreme cold. I haven't switched over to the synthetics, yet, because even with the many cold starts, I have not had any failures of any of my previous vehicles that was due to oil problems.

[glenmore]

I personally consider Amsoil and other high-priced synthetic fluids to be a huge waste of money.

I don't think there is any question as to whether Mobil and Amsoil synthetics are better than regular motor oil. All the specs show that synthetics are better. The key question is, as you point out, "Are they worth it?" I think of it as a treat for the car and nothing more. I do the fluid changes myself and only buy Mobil 1 on sale plus I joined the Mobil rebate club to help narrow the cost difference.

glenmore

1990 LS400

1991 300CE

2000 C280

[RedRocket]

I personally consider Amsoil and other high-priced synthetic fluids to be a huge waste of money.

I don't think there is any question as to whether Mobil and Amsoil synthetics are better than regular motor oil. All the specs show that synthetics are better. The key question is, as you point out, "Are they worth it?" I think of it as a treat for the car and nothing more. I do the fluid changes myself and only buy Mobil 1 on sale plus I joined the Mobil rebate club to help narrow the cost difference.

glenmore

1990 LS400

1991 300CE

2000 C280

As one who has taken the science approach to the oil (synthetic/petro) question. On my 99 SC400, I ran a series of tests with Mobil 1, Amsoil and Castrol GTX. After each run, I drained the oil and had it analyzed by a lab in Oakland , CA.

Castrol GTX is BAD after 5000 miles, thus 3000 would not be a bad change interval.

Mobil 1 could run for 10K miles and still be considered serviceable but with a low level of additives. Amsoil could be run for the same 10K miles but had a higher level of additives remaining. Both synths had a TBN (total base number) indicating serviceable oil. Both synths had lower metal particle counts than the Castrol.

My engine had very balanced compression (+/- 2 PSI) on all eight cylinders and burned no appreciable oil for all these tests and it's life.

Here is my conclusion. Synthetics pay off for long drain cycles (10K miles). The Amsoil method of changing the filter and adding a quart maintains the anti-wear additives BUT if there is a problem, like fuel / coolant dilution, the problem is compounded by not doing a complete drain.

I run a pure synth of wide viscosity range (10-50) and do a complete change on 10K miles PLUS use a very good filter (not FRAM).