rx300leo Posted May 2, 2006 Share Posted May 2, 2006 Would you please advice if there is any benefit of using synthetic gear oil for front and rear differentials (may be just longer service) on RX300 AWD vs traditional oil. While I was on a long business trip, my wife brought the car to a dealer for a very small unrelated issue and asked this question (as she new I was planning to do it). The answer was that Lexus does not reccomend the synthetic oil (which does not make any technical sence to me). What is your opinion. Would the synthetic gear oil make it easy on the transmission? I would appreciate your answer. Quote Link to comment Share on other sites More sharing options...
Grumpa72 Posted May 3, 2006 Share Posted May 3, 2006 Corvette and Porsche specify synthetics in their engines. Wonder why? I have used sythetics in all of my cars for years, including manual transmission, differential, and engine. This ranges from a recently sold 1979 Mercedes diesel, my 1972 Corvette, my 1997 Mustang, and my '05 330. I can't imagine why Lexus/Toyota specify dino oil only. Go to Mobils site and look at their data and info on synthetics. They even claim that their auto transmission fluid is compatible with Toyota's requirements. So far, I haven't changed to that since my car is still under 20000 miles. Gary Quote Link to comment Share on other sites More sharing options...
TunedRX300 Posted May 3, 2006 Share Posted May 3, 2006 Gary is right. Both Amsoil and Mobil have ATF that are T-IV compliance. http://www.amsoil.com/StoreFront/atf.aspx http://www.mobil.com/USA-English/Lu...il_ATF_3309.asp I believe skperformance tried with Mobil 1 Synthetic ATF, which is not T-IV compliance in his ES and has shift problem. I would stick with Amsoil Synthetic ATF and don't let Lexus or other flag waving members scare you into this "non-OEM fluid will cause your tranny to fail" when they can't provide scientific proof or oil analysis result. Quote Link to comment Share on other sites More sharing options...
Lexusfreak Posted May 3, 2006 Share Posted May 3, 2006 Gary is right. Both Amsoil and Mobil have ATF that are T-IV compliance. http://www.amsoil.com/StoreFront/atf.aspx http://www.mobil.com/USA-English/Lu...il_ATF_3309.asp I believe skperformance tried with Mobil 1 Synthetic ATF, which is not T-IV compliance in his ES and has shift problem. I would stick with Amsoil Synthetic ATF and don't let Lexus or other flag waving members scare you into this "non-OEM fluid will cause your tranny to fail" when they can't provide scientific proof or oil analysis result. I knew that Amsoil has a compatible ATF to meet Toyota Type IV fluids specs.....was not aware of M1 having one now however. I thought this was a question on conventional vs. Synthetic diff fluids? I installed Castrol Syntec 75w90 (meets GL-5 classification) in my wife's 2003 Subaru Forester for both the F & R diffs.......never had a problem before on conventional, but it's even slightly quieter now that I put the synthetic in. What does your owners manual say to use? B) Quote Link to comment Share on other sites More sharing options...
TunedRX300 Posted May 3, 2006 Share Posted May 3, 2006 Mobil ATF 3309 is not synthetic. From above links, the flash point of Amsoil is higher than Mobil's: 227 degree C vs. Mobile ATF's 185 degree C. I believe all who had a RX tranny failure or forced to drain and fill every 15k due to burned Toyota T-IV would benefit from additional temperature endurance. If anyone can find data sheet for Toyota T-IV, please post so we can compare. Quote Link to comment Share on other sites More sharing options...
Lexusfreak Posted May 3, 2006 Share Posted May 3, 2006 Mobil ATF 3309 is not synthetic. From above links, the flash point of Amsoil is higher than Mobil's: 227 degree C vs. Mobile ATF's 185 degree C. I believe all who had a RX tranny failure or forced to drain and fill every 15k due to burned Toyota T-IV would benefit from additional temperature endurance. If anyone can find data sheet for Toyota T-IV, please post so we can compare. I'd be curious to see those results as well. Quote Link to comment Share on other sites More sharing options...
lenore Posted May 3, 2006 Share Posted May 3, 2006 I have replaced the front and rear differentials with 75-90 w Synthetic and swear the car is quieter, dont know why, or maybe it is one of the placebo effects. Quote Link to comment Share on other sites More sharing options...
Lexusfreak Posted May 3, 2006 Share Posted May 3, 2006 I have replaced the front and rear differentials with 75-90 w Synthetic and swear the car is quieter, dont know why, or maybe it is one of the placebo effects. I concur.....I noticed the same thing. B) Quote Link to comment Share on other sites More sharing options...
rx300leo Posted May 3, 2006 Author Share Posted May 3, 2006 Mobil ATF 3309 is not synthetic. From above links, the flash point of Amsoil is higher than Mobil's: 227 degree C vs. Mobile ATF's 185 degree C. I believe all who had a RX tranny failure or forced to drain and fill every 15k due to burned Toyota T-IV would benefit from additional temperature endurance. If anyone can find data sheet for Toyota T-IV, please post so we can compare. I'd be curious to see those results as well. lenore, which brand of the Synthetic you used. I am considering Lucas, Red Line or Mobil one? Guys, thank you for the answer, but the question was about front and rear differentials, so it was about gear oil. Which brand did you use for that? Gary is right. Both Amsoil and Mobil have ATF that are T-IV compliance. http://www.amsoil.com/StoreFront/atf.aspx http://www.mobil.com/USA-English/Lu...il_ATF_3309.asp I believe skperformance tried with Mobil 1 Synthetic ATF, which is not T-IV compliance in his ES and has shift problem. I would stick with Amsoil Synthetic ATF and don't let Lexus or other flag waving members scare you into this "non-OEM fluid will cause your tranny to fail" when they can't provide scientific proof or oil analysis result. I knew that Amsoil has a compatible ATF to meet Toyota Type IV fluids specs.....was not aware of M1 having one now however. I thought this was a question on conventional vs. Synthetic diff fluids? I installed Castrol Syntec 75w90 (meets GL-5 classification) in my wife's 2003 Subaru Forester for both the F & R diffs.......never had a problem before on conventional, but it's even slightly quieter now that I put the synthetic in. What does your owners manual say to use? B) Quote Link to comment Share on other sites More sharing options...
Lexusfreak Posted May 3, 2006 Share Posted May 3, 2006 I'd stay clear of Lucas personally.......they are not highly rated on my other sites at all.....some have complained of foaming issues too. The most popular are Amsoil, M1 & Motul for synthetics........although these were not very easily available in my area (& when I could find them, they wanted astronomical prices for them). I ended up with Castrol Syntec 75W 90 gear oil & not one complaint & the price was right for a quality product which I would use again. B) Quote Link to comment Share on other sites More sharing options...
rx300leo Posted May 3, 2006 Author Share Posted May 3, 2006 I'd stay clear of Lucas personally.......they are not highly rated on my other sites at all.....some have complained of foaming issues too. The most popular are Amsoil, M1 & Motul for synthetics........although these were not very easily available in my area (& when I could find them, they wanted astronomical prices for them). I ended up with Castrol Syntec 75W 90 gear oil & not one complaint & the price was right for a quality product which I would use again. B) Thank you. Quote Link to comment Share on other sites More sharing options...
monarch Posted May 3, 2006 Share Posted May 3, 2006 rx300leo, for 35 years Toyota differentials have been lasting over 500,000 miles when lubricated with coonventional gear oil (and changing it roughly every 50,000 miles). But if you want to use a synthetic anyway, Toyota dealers carry a fully synthetic "Toyota Genuine Differential Gear Oil" Toyota part number 00289-75140 that is, according to the label "Specially formulated by Toyota for Toyota Vehicles" Quote Link to comment Share on other sites More sharing options...
Grumpa72 Posted May 3, 2006 Share Posted May 3, 2006 I thought this was a question on conventional vs. Synthetic diff fluids? I installed Castrol Syntec 75w90 (meets GL-5 classification) in my wife's 2003 Subaru Forester for both the F & R diffs.......never had a problem before on conventional, but it's even slightly quieter now that I put the synthetic in. What does your owners manual say to use? B) It is a discussion of diff fluids. I inadvertantly hijacked it when I continued the discussion to include synthetic engine oil and A/T fluid. FWIW, I use Mobil 1 synthetic diff lube in all of my cars that have a need for it. Obviously, most front wheel drive cars don't. Gary Quote Link to comment Share on other sites More sharing options...
lenore Posted May 3, 2006 Share Posted May 3, 2006 Mobil ATF 3309 is not synthetic. From above links, the flash point of Amsoil is higher than Mobil's: 227 degree C vs. Mobile ATF's 185 degree C. I believe all who had a RX tranny failure or forced to drain and fill every 15k due to burned Toyota T-IV would benefit from additional temperature endurance. If anyone can find data sheet for Toyota T-IV, please post so we can compare. I'd be curious to see those results as well. lenore, which brand of the Synthetic you used. I am considering Lucas, Red Line or Mobil one? Guys, thank you for the answer, but the question was about front and rear differentials, so it was about gear oil. Which brand did you use for that? Gary is right. Both Amsoil and Mobil have ATF that are T-IV compliance. http://www.amsoil.com/StoreFront/atf.aspx http://www.mobil.com/USA-English/Lu...il_ATF_3309.asp I believe skperformance tried with Mobil 1 Synthetic ATF, which is not T-IV compliance in his ES and has shift problem. I would stick with Amsoil Synthetic ATF and don't let Lexus or other flag waving members scare you into this "non-OEM fluid will cause your tranny to fail" when they can't provide scientific proof or oil analysis result. I knew that Amsoil has a compatible ATF to meet Toyota Type IV fluids specs.....was not aware of M1 having one now however. I thought this was a question on conventional vs. Synthetic diff fluids? I installed Castrol Syntec 75w90 (meets GL-5 classification) in my wife's 2003 Subaru Forester for both the F & R diffs.......never had a problem before on conventional, but it's even slightly quieter now that I put the synthetic in. What does your owners manual say to use? B) I used Castrol OIl synthetic sold at Walmart for about $8 per quart, YOU will need two bottles to due both from and back. Quote Link to comment Share on other sites More sharing options...
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