Satisfies the gear oil viscosity requirements of 75W90, 80W90, 90 and motor oil viscosities of SAE 40, 10W40 and 15W40 Appropriate coefficient of friction for most manual transmission synchronizers (other's synthetic gear oils are often too slippery for proper synchro engagement)

not trying to justify a switch away from the use of Redline here ... just wondering out loud as to why Redline has earned such a fine reputation).

About Klarna

Satisfies the gear oil viscosity requirements of 75W90, 80W90, 90 and engine oil viscosities of SAE 40, 10W40 and 15W40 Appropriate coefficient of friction for most manual transmission synchronisers (other’s synthetic gear oils are often too slippery for proper synchro engagement) Popular amongst rotary owners Redlines MT-90 is a GL-4 Gear oil suited for your transmission/gearbox. Being GL-4 its ideal if your worried about the risk of some GL-5 oils prematurely/rapidly wearing or damaging your synchro’s (please note that Idemitsu Racing MTF 75w90 is a GL-5 that will not prematurely/rapidly damage wear your synchro’s)Something that cannot be said for all GL-5 Gear Oils when put in some transmissions like those found in the RX-8 RED LINE MT-90 HIGH-PERFORMANCE GEAR OIL is a full-synthetic ester-based lubricant designed for use in manual transmissions and front-wheel-drive transaxles. This shear-stable formula resists breakdown for extended periods and offers more consistent viscosity in warm and cold temperatures for less gear noise and improved shifting. This fluid is less slippery for improved synchronizer coefficient of friction and offers stronger film strength for better wear protection.

High performance gear protection giving longer synchro life and eliminating notchy shifting, even when cold. Satisifies the gear oil viscosity requirements of 75W, 80W and motor oil viscosities of SAE 40, 10W40, and 15W40. Recommended for GL-1, GL-3, and GL-4 applications, as well as where most special synchromesh fluids are specified. Appropriate coefficient of friction for most manual transmission synchronizers (other's synthetic gear oils are often too slippery for proper synchro engagement). https://cdn.opieoils.co.uk/images/variants/medium/redline/red-line-mt90-75w-90-gl4-synthetic-manual-gear-oil-1-us-gallon-378-litres-1.jpg An old post by Keoke on this forum recommended Valvoline VR1 60W in the summer and 50w in the winter. I put in 60w and that fixed the o/drive problem that you described on my car. If MT90 fixed it on yours then your accumulator seals are not quite as worn as mine apparently are. Red line MT90 is a synthetic 75W90oil designed for use in synchromesh gearboxes. It provides excellent protection to gears and improves the life of synchro rings. It has a perfect coefficient of friction to allow easier and faster gear changes even when cold. Recommended for GL-1, GL-3 and GL-4 applications, as well as where most special synchromesh fluids are specifiedhttps://cdn.opieoils.co.uk/images/variants/icon/redline/red-line-mt90-75w-90-gl4-synthetic-manual-gear-oil-1-us-gallon-378-litres-2.jpg I switched to redline MT90. That didn't cure the o/drive problem but the transmission seemed to shift a little smoother... https://cdn.opieoils.co.uk/images/variants/icon/redline/red-line-mt90-75w-90-gl4-synthetic-manual-gear-oil-1-us-quart-0946-litre-2.jpg Under this hypothesis, any given brand of oil would allow the tranny to work just the same as another, so long as the viscocity of both fluids are kept equal. RED LINE MT-90 HIGH-PERFORMANCE GEAR OIL is a fully-synthetic ester-based lubricant designed for use in manual transmissions and front-wheel-drive transaxles. This shear-stable formula resists breakdown for extended periods and offers more consistent viscosity in warm and cold temperatures for less gear noise and improved shifting. This fluid is less slippery for improved synchroniser coefficient of friction and offers stronger film strength for better wear protection.

https://cdn.opieoils.co.uk/images/variants/icon/redline/red-line-mt90-75w-90-gl4-synthetic-manual-gear-oil-1-us-quart-0946-litre-3.jpg https://cdn.opieoils.co.uk/images/variants/large/redline/red-line-mt90-75w-90-gl4-synthetic-manual-gear-oil-1-us-quart-0946-litre-2.jpg

I think that Dave said MT90 is somewhat equivalent in viscosity to 40w motor oil. If your o/drive starts acting up again when it gets real hot, try switching to 60w valvoline VR1. https://cdn.opieoils.co.uk/images/variants/medium/redline/red-line-mt90-75w-90-gl4-synthetic-manual-gear-oil-1-us-quart-0946-litre-1.jpg