'41 Fat Bottom Girl Posted April 25, 2020 Report Share Posted April 25, 2020 When changing to a synthetic standard transmission oil...Any concerns with the residual conventional 90W oil left in the tranny after draining? Would it be advisable to run the new synthetic for a bit, drain the tranny again and refill with fresh synthetic? Thx! Quote Link to comment Share on other sites More sharing options...
Sam Buchanan Posted April 25, 2020 Report Share Posted April 25, 2020 (edited) 18 minutes ago, '41 Fat Bottom Girl said: When changing to a synthetic standard transmission oil...Any concerns with the residual conventional 90W oil left in the tranny after draining? Would it be advisable to run the new synthetic for a bit, drain the tranny again and refill with fresh synthetic? Thx! Best info is from the manufacturer. Here is a quote from Red Line's Tech paper on their gear oils: "It is not necessary to flush the transmission before replacing with MTL. Remove the drain plug and drain while warm. Seal compatibility has been designed to be similar to petroleum lubricants, and leakage should be no greater than any other oil of comparable viscosity. Being formulated with extremely stable synthetic basestocks, MTL and MT-90 will last much longer than conventional petroleum lubricants." The entire paper can be found here, and it is an interesting read: https://www.redlineoil.com/Content/files/tech/MTL and MT-90 Tech Info.pdf Edited April 25, 2020 by Sam Buchanan Quote Link to comment Share on other sites More sharing options...
Sniper Posted April 25, 2020 Report Share Posted April 25, 2020 I wonder if Red Line looked at old seal technology like what we have? I don't imagine they wasted their time. Quote Link to comment Share on other sites More sharing options...
Sam Buchanan Posted April 25, 2020 Report Share Posted April 25, 2020 (edited) 14 minutes ago, Sniper said: I wonder if Red Line looked at old seal technology like what we have? I don't imagine they wasted their time. Why should they if their product compatibility is similar to petroleum products........ Edited April 25, 2020 by Sam Buchanan Quote Link to comment Share on other sites More sharing options...
Sniper Posted April 25, 2020 Report Share Posted April 25, 2020 compatible with what is the point. Modern seal technology uses different materials than our old stuff came with. If they tested modern seals and found that is has similar compatibility as petroleum, yay for modern seals. Doesn't mean it has it with the old stuff too and the phrase "similar too" is really undefined as well. It could mean similar to petroleum products when used on engines built since 1990, or pick a date. It's what's called weasel words. Seems to say what you want to hear but if you parse it then you find it really doesn't say anything of value. Quote Link to comment Share on other sites More sharing options...
Sam Buchanan Posted April 26, 2020 Report Share Posted April 26, 2020 Ok....................... Quote Link to comment Share on other sites More sharing options...
Nick307 Posted April 26, 2020 Report Share Posted April 26, 2020 In my opinion (Big emphasis on opinion) as a mechanic. Switching from non detergent oil to detergent oil or regular detergent oil to synthetic, both have pros and cons. If your engine has been run on 30w non detergent its whole life and you suddenly switch to let's say 15w40 full synthetic. You will have oil leaks from your seals and possible oil pump failure or clogged oil galleries due to the fact that all the sludge build up will start cutting loose and synthetics dont have the same oil seal swell properties as non synthetics. BUT on a fresh rebuild and reseal you would be good to switch to a modern oil. Just remember to upgrade to a modern filtration system when you do so. Quote Link to comment Share on other sites More sharing options...
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