Thinner differential oil for RWD car? ('06 Miata)

[dremd]

The 75w90 was the one I was eluding to earlier.
If you search around on tdi club for stick with g52 in your trans you will find that it is pretty darn thin 50-60 actual.
That said the stuff I run is thinner still (oe VW drw fluid).

[1337]

Originally Posted by Bror Jace

Red Line Synthetic Oil - Gear Oil for Differentials - 75W85 GL-5 Gear Oil

Nice find! According the the Red Line specs, it's roughly the same viscosity as GM Synchromesh. As you mentioned, this is GL-5 instead of GL-4, so the additives package should be suited for a differential.

Originally Posted by Bror Jace

I think with a Miata, though, you're #1 enemy is wind resistance. I love my convertible, but it's an affront to the aero gods.

Very true. Any thoughts on aero mods for a Miata?


Good point. P.S. When I was replacing my Jetta TDI, I narrowed it down to (1) an other TDI, (2) a 1st gen Insight, or (3) a Miata. I decided I would be "officially un-adventerous" if I owned two of the same car (TDI). According to some back-of-the-napkin calculations, the Miata and Insight should have similar fuel&maintenance costs (though Insight is still cheaper) if you factor in the Insight needing a $1500+ battery every 80k miles.

[1337]

Originally Posted by dremd

The 75w90 was the one I was eluding to earlier.
If you search around on tdi club for stick with g52 in your trans you will find that it is pretty darn thin 50-60 actual.
That said the stuff I run is thinner still (oe VW drw fluid).

Good point. BTW, did you do a 6-speed swap in your TDI? What was the donor car?

[Bror Jace]

I love the Miata, but as a hypermiler vehicle, it is poorly suited. The roofline is simply not at all aerodynamic ... even with the top-up. Plus, the fabric buffeting adds drag. Adding the factory hard-top gets rid of the buffeting, but you still end up with a bubble-shape sticking straight up from the chassis in the air stream.

I have a Honda S2000 ... even more poorly suited than the Miata because of the increased engine size/power and added weight. One thing I have seen on an S2000 is a fastback hardtop. This is not a simple mod ... more like a transformation of the car. Some examples:

http://www.superhonda.com/photopost/...s_s2kchop1.jpg

ImageShack® - Online Photo and Video Hosting

S2000 fastback image by aceone73 on Photobucket

Despite the loss of open-top fun, the cars look incredible.

The same treatment, though not as dramatic, is available for Miatas:

http://www.clubmiatamonteregie.ca/mc11.jpg

And some discussion:

Miata fastback!: Grassroots Motorsports forum: Grassroots Motorsports Magazine

I will strongly consider a fastback mod for my next S2000.

[1337]

Originally Posted by Bror Jace

I love the Miata, but as a hypermiler vehicle, it is poorly suited. The roofline is simply not at all aerodynamic ... even with the top-up. Plus, the fabric buffeting adds drag. Adding the factory hard-top gets rid of the buffeting, but you still end up with a bubble-shape sticking straight up from the chassis in the air stream.

True. I wish the US market had aerodynamic diesels and hybrids that offer telepathic steering, good driver involvement, precise gearboxes, RWD, and great reliability. Instead, we get a bunch of mushy, beige, wrong-wheel-drive hybrids with automatics and CVTs.

Originally Posted by Bror Jace

I have a Honda S2000 ... even more poorly suited than the Miata because of the increased engine size/power and added weight. One thing I have seen on an S2000 is a fastback hardtop. This is not a simple mod ... more like a transformation of the car.

I like the fastback idea. I've seen at least one company that produced a fastback hardtop for the 1989-1997 (NA) and 1999-2005 (NB) Miatas. Alas, nobody seems to have produced a fastback hardtop for the 2006+ (NC) Miata. I think it would be difficult to DIY a hardtop.

Also, just out of curiosity, what is your S2000's typical MPG?

Originally Posted by Bror Jace

The same treatment, though not as dramatic, is available for Miatas:

That picture of the yellow hardtop Miata often shows up in Miata forums. Unfortunately, it was a one-off car. It could be replicated, but it would be a tall order for a DIYer to get it just right. Notice that the roof flows seamlessly into the bodywork.

[Ladogaboy]

As far as I understand it, GL-5 can be used for both GL-4 and GL-5 applications, but not the other way around. Is that correct?

[minispeed]

1337, did you end up replacing the diff oil? This is one of my planned mods on my 93 miata and I was wondering what you used and what mpg gains you got out of it?

[pjbgravely]

Originally Posted by Ladogaboy

As far as I understand it, GL-5 can be used for both GL-4 and GL-5 applications, but not the other way around. Is that correct?

Not always. The GL-4 rating is also safe for yellow metals, GL-5 doesn't have to be. If you have something old with Bronze gears or bushings you need something with a GL-4 rating. Oil can have both ratings at the same time.

[1337]

Originally Posted by minispeed

1337, did you end up replacing the diff oil? This is one of my planned mods on my 93 miata and I was wondering what you used and what mpg gains you got out of it?

Nah. I changed it recently, but I'm still using the factory-spec stuff. Got a little nervous about premature wear with thinner fluid.

Looking forward to hearing about the 93 Miata!

[minispeed]

Originally Posted by 1337

Nah. I changed it recently, but I'm still using the factory-spec stuff. Got a little nervous about premature wear with thinner fluid.

Looking forward to hearing about the 93 Miata!

The 93 is gone, had a baby and the wife got freaked about the safety of an.older car after it got a fuel leak. Have a 12 kia optima now