They will tell you that you can increase so long as they don't see anything indicating a problem in the sample. They assume that you are looking to maximize your oil change interval.Blackstone is recomending me to go above 7500 mile interval oil change I dont know if I risk it.
Could be any number of reasons for the slightly lower viscosity. Measuement variations, more highway, racing, lower to start with on the 2nd change, anti-freeze contamination in the 1st sample, etc. http://www.blackstone-labs.com/oil-viscosity.phpalso why is the oil viscosity so much lower this time?
and what the heck is insoluble %?
Yes & yes. If you go to MT-90, I'd pick up like 8 or 9qts and plan on doing some short interval changes (like 15K) to clean things out. It has steadily improved on each of my changes. I haven't had it tested. But, at a 30K interval (now), it looks just fine coming out (I just changed it not long ago).You are using MT-90 correct 2 way? Do you like it a lot better than the standard dino oils?
They sort of have that backwards. While the 75W-90NS does not have the friction modifiers. The NS is the one that is designed for non slip LSD applications. The MT-90 has friction modifiers for proper synchro engagement. MT-90 75W-90 is a GL-4, 75W-90NS is a GL-5 oil. See: http://www.redlineoil.com/content/files/tech/MTL and MT-90 Tech Info.pdfThis is the reasoning; MT-90 has friction modifiers for limited-slip transaxles which makes the gear oil more viscious and in the process harder for syncros to match speed.The 75w-90ns not having these modifiers
Probably not. It is also a GL-5/MT-1. While our manual trannies are spec'd for GL-4/GL-5. They seem to like the GL-4 better. There's also more of a chance of problems with synchro deteriotion with the additives in some(not all) GL-5's. Also, MT-90 is specifically designed for transmissions vs. a general use gear oil.I also read there is a castrol synthetic gear oil that may be available locally. Would that be a good one to use?
Redline Oil said:Most manufacturers of manual transmissions and transaxles recommend an 80W or 90W GL-4 lubricant. GL-5 gear oils which are required in hypoid differentials are not used in most synchromesh transmissions because the chemicals used to provide the extreme pressure protection can be corrosive to synchronizers, which are commonly made of brass or bronze. Typically, the use of a GL-5 lubricant in a synchromesh transmission will shorten the synchronizer life by one half. The extreme pressure requirements of spur gears and helical gears found in transmissions are not nearly as great as found in rear-wheel drive differentials. A GL-4 lubricant provides adequate protection for most manual transmissions, unless a unique design consideration requires the extra protection of a GL-5.
Approximately $30-$40 every 30K, if you go short interval (other than the initial changeover).... every 60K if you go a standard interval. I don't see that as a whole lot of $, given the time frames.What would be your other suggestion besides the MT-90, as it is pretty spendy stuff to be changing out too often? All the online sites charge you $10 + a usually high shipping charge.