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 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/medium/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/medium/redline/red-line-mt90-75w-90-gl4-synthetic-manual-gear-oil-1-us-gallon-378-litres-2.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. https://cdn.opieoils.co.uk/images/variants/medium/redline/red-line-mt90-75w-90-gl4-synthetic-manual-gear-oil-1-us-quart-0946-litre-2.jpghttps://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/medium/redline/red-line-mt90-75w-90-gl4-synthetic-manual-gear-oil-1-us-gallon-378-litres-1.jpg Where I live I'm a fan of MT90. But if you drive your car when it's cold outside MTL would likely be the best choice. If you have any doubts just call Redline-- I'm sure they'd happily advise you. In any case, you won't be regret installing either MTL or MT90. OK, I just went out to the garage and pulled my old blue binder factory service manual down off the shelf. 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 synchronizer 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-gallon-378-litres-2.jpg https://cdn.opieoils.co.uk/images/variants/icon/redline/red-line-mt90-75w-90-gl4-synthetic-manual-gear-oil-1-us-quart-0946-litre-1.jpg This Gear Oil is suitable and popular for most RX-8 and RX-7 Transmissions. MT-90 75W90 GL-4 GEAR OIL I found MTL around 20 years ago while trying to solve some crunchy gear engagement problems in a BMW. It solved the problem so well that I've been a Redline fan ever since. It ain't snake oil. It's an engineered product. https://cdn.opieoils.co.uk/images/variants/icon/redline/red-line-mt90-75w-90-gl4-synthetic-manual-gear-oil-1-us-gallon-378-litres-1.jpgUnder 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. Popular in Nissan, Mazda, Mitsubishi, VW/Audi, Lotus Elise/Exige, Toyota, Mendeola transmissions and Atlas transfer cases for Off Road Recommended for GL-1, GL-3 and GL-4 applications, as well as where most special synchromesh fluids are specified 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).

Recommendations: API GL-4 / GL-3 / GL-1, SAE 80W90, SAE 90, SAE 40W, SAE 10W40, SAE 15W40, Alfa Romeo, Audi G 052 911, BMW 81 22 9 407 305, Castrol BOT 130M, Castrol BOT 328, Castrol SAF AG4, Castrol SHC 630, Castrol TAF-X 75w-90, Castrol Syntrans Transaxle 75W-90, Ford F32Z-19C547-MA, Ford M2C175-A, Ford M2C200-B, Ford WSS-M2C203-A1, Ford XT-4-QGL, GM 12345371, GM 12345724, GM 12345871, GM 12346074, GM 89021806, GM 89021807, GM-Daewoo EDS-M-8049, Holden, Hyundai/Kia 08950-00010-A, Hyundai/Kia 04300-5L1A0, Jeep 0489722AA, Lotus, Mazda (MES) 115A, Mazda 0000-77-114-QT, Mazda L.L. Manual Gear Oil IS, MB A 001989510310, Mitsubishi, Nissan Mission Oil MP-G HQ, Opel, Skoda, Toyota 08885-80917, Toyota 08885-81023, Toyota 08885-81026, Vauxhall, VW/Audi G 005 000 , VW/Audi G 005 100, VW/Audi G 045 190 A2, VW/Audi G 052 145, VW/Audi G 052 157, VW/Audi G 052 911, VW/Audi G51, VW/Audi G50, VW/Audi 501.5 https://cdn.opieoils.co.uk/images/variants/large/redline/red-line-mt90-75w-90-gl4-synthetic-manual-gear-oil-1-us-quart-0946-litre-1.jpg

Satisfies the gear oil viscosity requirements of 75W90, 80W90, 90 and motor oil viscosities of SAE 40, 10W40 and 15W40 I've read about some of us using Redline instead of straight weight 30 non detergent oil in our transmission. I'll assume most of the transmissions have the overdrive.

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). Based upon the weights of the MTL vs. MT90, looks like the MT90 better meets the 90 weight spec, so there you go!Bob... That problem that you describe, " when hot, o/drive doesn't engage " is exactly what I had experienced with regular 30w motor oil. IIRC, Redline says flat out that the only difference between MTL and MT90 is the viscosity/intended temp range. Like Steve says, if the car is driven hard or lives in a hot climate, MT90 is prolly a better choice. But frankly, we've run MTL in BMW race cars where the trans tunnel actually gets too hot to touch in the summer, and never seen a problem. This 70W80 GL-4 Gear Oil (SAE 5W30/10W30 engine oil viscosity) is designed for use in manual transmissions and transaxles. Provides excellent protection of gears and synchronizers and its balanced slipperiness provides a perfect coefficient of friction, allowing easier shifting. Popular in many BMW transmissions and in most Honda and Acura transaxle applications. Several here, including myself, have used motor oil in X transaxles, often in lower viscosities than MTL. Bur MTL works better, regardless of weight. It's one of those rare products that works as claimed.