Red Line 50304 Manual Transmission (MT) 90W Gear Oil - 1 Quart

by Red Line

Product Features

• Helps prevent hard shifting
• Synthetic
• Provides excellent protection
• Improved shiftability

Product Details

• Shipping Weight: 2 pounds (View shipping rates and policies)
• Shipping: This item is also available for shipping to select countries outside the U.S.
• ASIN: B000CPCBEQ
• Item model number: 50304
• Average Customer Review: 4.8 out of 5 stars  See all reviews (40 customer reviews)
• Amazon Best Sellers Rank: #450 in Automotive (See Top 100 in Automotive)
  • #1 in Automotive > Oils & Fluids > Oils > Gear Oils

Product Description

Red Line Oil MTL and MT-90 are designed to provide excellent protection and improved shiftability for manual transmissions and transaxles, having cured the problem of hard shifting in thousands of transmissions with shifting troubles. They have the appropriate coefficient of friction for most manual transmission synchronizers (many gear oils, engine oils, and ATFs are too slippery for proper synchro engagement). And, the wide viscosity of MTL and MT-90 allow proper shifting over the entire temperature range which the transmission will experience. The synthetic base oils used have a very high viscosity index which provides relatively constant viscosity as temperature changes. MTL is a low 70W at very low temperatures and a high 80W, nearly an 85W, at elevated temperatures, providing adequate viscosity to prevent wear and deaden gear noise. MT-90 is a thicker 75W90 version of MTL. The shear stability and oxidation stability of these products are excellent, thus the physical characteristics of Red Line MTL and MT-90 will change little with use.

Customer Reviews

Most Helpful Customer Reviews

21 of 21 people found the following review helpful:

5.0 out of 5 stars Best GL-4 fluid there is. Do not use GL-5 fluid if GL-4 is specified!, January 22, 2010

By 

Re-view-eR - See all my reviews

Amazon Verified Purchase

This review is from: Red Line 50304 Manual Transmission (MT) 90W Gear Oil - 1 Quart (Automotive)

This is one awesome GL-4 fluid. It does everything it is supposed to and more, just as Redline promised. It smoothed out my transmission that I thought was potentially damaged. I was skeptical at first but no more. It was also cheaper than very expensive (and wrong, for my car) fluids at all the local stores that they tried to sell me.

Some background info is in order, if you are interested.

Many think all gear lube is the same, as long as you pick the right weight. Even many mechanics pay no attention to anything other than weight. Well, wrong, although it used to be true. Unlike motor oil, gear lube is indeed made different for different applications, even for the same weights, as newer cars requirements are so different from older cars.


Mistake one: I had a pro shop change the gear lube in a manual tranny pushing close to 200k.I figured it was time :) If you want it done right, do it yourself, but I was lazy that day. I specifically requested them to make sure the right synthetic fluid went in. They of course put in the right weight: high priced, major brand, synthetic 75w90, but they never bothered to check anything else, since they just have the autostore cross-reference and deliver the fluid. The stores are more clueless than anything else. The chain stores do not even stock GL-4 fluid anymore. There was one high priced brand that claimed to be both GL-4 and GL-5. Well, anything that claims to be one size fits all usually does not fit anything properly so I would stay away from that.


Mistake two: Not checking if all lube was backward compatible. If you want to be sure, check everything yourself. After all, I had professionals do it for me, right? They don't care because it is not their car. Well, GL-5 is not backward compatible and can actually damage some tender parts in transmissions designed for GL-4 due to some harsh additives.

So, after the shop put in GL-5, after a week or two, tranny started lurching in 5th gear. Darn. Did some research, but could not be sure if it was the fluid or just coincidence. After all, it is a lot of miles on the tranny. But, all indications were GL-5 was bad for my GL-4 designed transmission.
So, all my hopes rested on this Redline fluid. It did not let me down!

Got some Redline MT-90 GL-4 75w90 fluid and changed it myself. Amazon has the best price. No one locally even stocked pure GL-4. At first, the lurching was still there. Well, it was worth a try, I thought. But then, it got smoother, or so it seemed. Wishful thinking, I thought. Then, it was definitely smoother, no mistake. Could it be? Now, about two weeks after, for the very first day, the lurching in 5th gear is completely gone, and the tranny is as smooth as it was before. Even smoother. I would occasionally grind when shifting quickly, but now I can shift as fast I am capable of and I have yet to make it grind.

So, expensive lessons learned.

One, do it yourself, if you can. Check what someone else puts in your car before you let them put it there. Definition of a "professional" is that they are paid to do it, not necessarily that they do it well. Just because they get paid to do it, does not mean they know what they are doing, or know better than you.

Two, even if you do not do it yourself, at least make sure your mechanic knows what to put in. They will not take time to research and could not care less if you do not tell them beforehand.

Three, do not trust clueless autostores to cross-reference fluids. They will get it wrong most of the time. Go to factory service manuals or other reliable sources for that information.

Four, if your transmission calls for GL-4, do not chance it with GL-5! Brass synchronizers cannot take it, as GL-5 additives can eat them. You may need a new tranny or major repairs before you know it.

6 of 6 people found the following review helpful:

5.0 out of 5 stars Good product, February 3, 2010

By 

Robert L. Kalb (French Lick,IN) - See all my reviews
(REAL NAME)   

Amazon Verified Purchase

This review is from: Red Line 50304 Manual Transmission (MT) 90W Gear Oil - 1 Quart (Automotive)

I had put in royal purple in my trans didn't like it to slick 3rd gear wanted to grind a little when cold in the morning. The redlline mt-90 much better the trans feels a lot smoother.When I start it up in the morning it will go right into reverse with out clutching it first.Before I always had to put it in neutral and let the clutch out once before it would go into reverse very good gear oil.I think it would be hard to find a better one.

5 of 5 people found the following review helpful:

5.0 out of 5 stars good lubricatn, September 15, 2009

By 

Ilya Bereznyak (Mile above rest, CO) - See all my reviews
(REAL NAME)   

Amazon Verified Purchase

This review is from: Red Line 50304 Manual Transmission (MT) 90W Gear Oil - 1 Quart (Automotive)

I have had redline fluids in my cars since early 90's. Recently I switched to royal purple, simple because the nearest redline dealer is a 50 mile round trip, while RP is at nearest NAPA.
I had transmission rebuilt by a dealer after 50k miles due to grinding noise when shifting into 5th. (I had factory gear oil, changed to Royal purple at 30K miles when I start experiencing early warning signs of tranny issues). My previous experience was that by putting a better lubricant in, I was able to address early issues. Well royal Purple didn't help and dealer after being a DEALER replaced the tranny. Well fast forward 67k miles... I just start experiencing early signs of grinding in 5th. Since Redline Line was in an identical car for over 100k miles (previous vehicle, obviously the fluid was changed at the appropriate intervals) and not an issue with identical transmission.
So got couple bottles ( price was 3 dollars less than somewhat local, no tax and no driving for 2+ hours in traffic to get 2 bottles).
The shift points became a tad more pronounce almost notchy, but still smooth and NO GRINDING! So for my little Korean car the redline is a miracle fluid :)

PS Not bad mouthing Royal purple, I just flushed rear end and transmission in other vehicle... but apparently Redline was/is/will be my best option :)