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How often should I change the gearbox oil?

Merlin Johnson (

About every 60k miles for normal oil...or get Redline sythetic and be done with it (like 100,000 miles or something)?

Is there a recommended interval between brake fluid changes?

Wayne Cox (

I aim for 6 months - 1 year on the SE-R, and about every 2 years on cars I'm not as concerned with. Road racers will change before every event.

Advice on cheap high temp fluid from the autocross mail list and Grassroots Motorsports Mag: Ford heavy duty DOT 3 fluid. Very high boiling point (despite conservative DOT3 label), low moisture absorption, and under $5 for 16 oz at Ford dealers. You can spend big $$$ on really high temp stuff, but these supposedly absorb moisture even faster, *requiring* you to change a few times per year. The temp of the ford stuff is plenty for street use.

About Redline MTL...

Merlin Johnson (

It is slippier, because of it design (molecules and stuff like that...they have a big tech sheet on that stuff). It lasts longer because of its design, it doesnt break down as easily under heat and stress (shearing and such) as real dino juice.

Real World Experience......your shifting feels smoother at all temps. That's it, you wont go faster. Longevity or if it will make your gearbox last longer???? Who knows. It just feels nice to have a smooth gear box...smoother than stock anyways.

What's the difference between MTL and MT-90?

Wayne Cox (

Redline says "MTL" is equivalent to 75W80 gear oil, and "MT-90" is 75W90. If you check your owner's manual or the shop manual, Nissan says 75W90 is the stuff to use in the temperatures encountered in most of North America.

Since this has come up alot lately lately, here's the blurb straight off a bottle of MT-90, which may explain some... Red Line Synthetic MT-90 is specially designed for manual transmissions and transaxles. The relatively constant viscosity over a wide temperature range allows easier shifting and helps prevent whine and rattle at high temperatures. Most gear oils, ATFs, and motor oils are too slippery for proper synchro engagement - which causes gear clash when shifting. .... MT-90 has a coefficient of friction which is perfect for rapid synchro engagement and allows high-speed upshifting and downshifting. ... Petroleum multigrade motor oils and transmissions fluids contain polymers which shear down rapidly under the action of gear teeth and rapidly lose viscosity , significantly reducing their lubricating ability . Red Line MT-90 is shear stable and will retain its physical characteristics for extended periods. MT-90 meets gear oil viscosities SAE 75W, 80W, and 90 or motor oil viscosities SAE 40 or 15W40 and provides gear protection which satisfies API categories GL-3 and GL-4.

How much is MT-90, how much do I need, and where can I get some?

Ken Baptiste (

I got it for $7.99 per quart and used exactly 4 quarts. Look in your yellow pages for "Automobile Performance, Racing & Sports Car Equipment" and start calling around. Someone will have it.

Two days ago I went to a dealer to buy brake fluid. I wanted to replace the DOT3 OEM fluid by the DOT5.1 Castrol fluid. The dealer mentioned that this kind of fluid might harm the ruber seals in the brake systems of DOT3 or DOT4 specification. Has anyone used DOT5.1 brake fluid in their SE-Rs? DOT5.1 brake fluids are glycol-based (like DOT3 & 4 ones), unlike DOT5 which are silicone-based. I will use the brake fluid for street driving not racing, so long-term performance is important.

Scott Reid (

I've heard from several people that to use DOT5 in DOT3/4 systems, you need to first replace some seals and gaskets in the brake system with ones which are designed for use with DOT5 fluid.

Maintained by Ronald S. Chong (