Differential Gear Oils
 

I'm due soon to change my Diff fluid this month. I've come down to a choice between 3 different fluids and I wonder what your thoughts might be on each of them. My current schedule is to change the diff fluid once per year. This is an '01 AP1 with ab out 96,000 miles on the clock. I've had it for 7 years starting out with 45K miles. Mostly city and highway driving in town. I've been to the track a few times, yet that was 5 years ago, and I'm not sure if I'll be able to return there anytime soon. I plan to keep the S for as long as possible. Last year I put in Mobil 1 LS 75W90. City trips include 5-6 miles one way to commute for work, cross-town jaunts of 30 miles one way, mostly freeway, day-trips (like group drives through canyons/mountain roads), and straight across the desert 400 miles from Phoenix, AZ to Southern California, for example, mostly Interstate Highways.

The fluids I'm considering for this year's change (and ongoing years) are the following:

Mobil 1 LS 75W-90
Amsoil sever Gear SAE 75W-110
Lubrication Engineers Duolec Vari-purpose Gear Lubricatnt 1605 ISO 220/SAE 110

What are your thoughts on these three fluids for the differential in a pretty much stock S?

Aren't we supposed to use the Honda fluid?

For a long time, Honda did not have the correct lubricant for the S2000 and dealers were putting in the wrong fluid and people had their differentials fail on them.

Apparently honda now has the correct fluid. I had a Honda dealer change the fluid in the car in 2015 before I knew about the issues. When I changed the fluid a few weeks ago, everything was hunky dory.

I just changed to the amsoil 110, and have been happy with it. I don't think diff oil will be something that you will really feel a difference in, it's more about the protection.

I refuse to pay a dealer to change the oil, transmission or differential fluids since is too easy to do those jobs myself. I was not aware that Honda now has diff fluid for the S. Most people that I have talked to seem to use one of the three fluids that I listed.

Dies anyone have thoughts positive or negative on these oils?

Stay away from any 75/90. The LE 110 or Amsoil 110 is good.
I have over 130k miles on my '06 and I use a 50/50 mix of M1 75/90 and 75/140 works out to be very close to a 75/110.

ROD

Thanks for the advise. Why is the 75/90 not advisable?

A lot of people feel the 90 is too thin. The 110 seems to be a good fit and you can go to the 140 if you plan to really work the car hard.

I agree about not having a dealer do it. It is pretty straightforward, once you buy the right sized wrench and socket. They are very large.

I have all of the tools to do the work myself. Wood ramps to drive the front end up onto, to allow the (not so) low profile jack to lift the front end onto hefty jack stands, followed by the rear end. Once up on all 4 jack stands the car is very steady. The correct size sockets and wrenches pay for themselves in one fluid change.

75/110 is the updated proper Honda spec. Or can use 75/140. Both are acceptable. I prefer 75/140 for the extra protection on my higher mileage diff that sees hard use. The viscosity should effect torsion engagement to some degree also. Thicker oil should offer a quicker positive engagement at both wheels. But its the hot weight that is thicker, not the cold weight.

75/110 is the updated proper Honda spec. Or can use 75/140. Both are acceptable. I prefer 75/140 for the extra protection on my higher mileage diff that sees hard use. The viscosity should effect torsion engagement to some degree also. Thicker oil should offer a quicker positive engagement at both wheels. But its the hot weight that is thicker, not the cold weight.

I have been using what ever full syn 75/140 thats on the shelf/on sale for years. Usually castrol.