Amsoil Question?

[archtop]

I'm thinking of going with Amsoil ( really not much more expensive than Mobil 1) and when I called their tech dept. they told me they recommend 5-40 European Bend? Also 75-90 Severe duty for the diff.? Sound right,I know we're supposed to use 10-30 but they say to use 5-40.

[emg88]

I'm using the 5-40 Amsoil and the Severe Gear 75-110 during the summer and 75-90 for the colder weather. I have no complaints. the Rear Diff is quieter with the 75-110.:thumbup:

[repiv]

Ed is proof positive that it works. If you look at your manual, you will see that 5W40 is good for ALL temp ranges. Many people have been using Mobil 1 75W90 in the S for years with great success. A similar wt. of Amsoil would also be good. Although 75W110 is not absolutely necessary, for summer and/or track use, it will have some benefits. Having said that, know that the manual does state a straight 90 wt. gear oil (GL-5). However, a multi-grade gear oil has proven itself to work quite successfully.

[emg88]

I like the 75-110 so much, I will try it in the colder weather. Here is what I based this on. I had the 75-90 in the car at 82 degs. I took an infrared temp reading before and after a specific drive. Changed the diff fluid to the 75-110. I took the before temp. The diff temp was higher to start since the housing was warm from the drive. I did the same drive, took the temp reading, Air temp was now 83. The diff temp was 17 degs lower after the same drive! Less heat = less friction=:)
The 75-110 should provide the same cold weather properties as the 75-90 so why change?

Could I be more scientific? Yes. Do I need to? I don't think so. I did everything I could to generate more heat in the diff. Accelerate hard, hard turns on the gas and tried to duplicate the drives as much as possible. I think I did that as well as you could on the street.:thumbup:

I am an Amsoil advocate. I first used it after my b-inlaw told me about the results in his Harley.
So I tried it in my Harley (104HP w/10.5 compression in an 80" motor - Pretty high strung for that size motor) I saw a real 20 deg reduction in operating temperature. My b-inlaw had similar results in his 107" motor. I was sold and still am!

[repiv]

^ Very interesting. This is the first time I've seen any kind of temp measurement. I think I'll switch to this weight next time. I have a temperature probe on my rear diff, so I can see a "running tally" on the temps.
You are right, the "75W" part will be the same in the cold as both fluids. Cold weather characteristics shouldn't change.
It is my understanding that viscosity numbers for gear oil is rated differently than for crankcase oil. EG, a 75W90 gear oil wouldn't be equivalent to a 75W90 engine oil (if one existed). A 75 wt. gear oil isn't 7.5 times more viscous (or thicker) than a 10 wt. engine oil, as a 90 wt. gear oil isn't 3 times more viscous as a 30 wt. engine oil.

[archtop]

Is it "better" to use 5-40 over 10-30 ? We do have winter here but its very mild 40-50 F daytime temps on average although the nights get down in the teen's.

[repiv]

Is it "better" to use 5-40 over 10-30 ? We do have winter here but its very mild 40-50 F daytime temps on average although the nights get down in the teen's.
I don't think it matters much for your type of weather. Personally, if I could get 5W40 easily, that's all I would use year roung. As it it, I use a full synthetic 10W30 now. I used to switch to full synthetic 5W30 in the cold months, but realize that I used to park the car outside overnight in temps as cold as -38*C and a 5w30 synthetic definately helped in the cranking department.
For you, a 10W30 would be fine. If you don't use synthetic, then I would go with a 5W30 for winter or the 5W40 all year. We consider even the low "teens" (on the F scale) to be a downright "balmy" winter night. I wouldn't even plug the thing in if that's as cold as it got. We don't generally start to plug the cars in till it got below 5*F.

[archtop]

There is no difference in price between the 5-40 and 10-30 .Is there any benefit to either in my case or is the choice just a flip of a coin?

[repiv]

There is no difference in price between the 5-40 and 10-30 .Is there any benefit to either in my case or is the choice just a flip of a coin?

If it were me and price was the same and it was easy to get, I would run 5W40 year round. You may have "hot" days during the winter and the 40 wt will provide a bit better protection when the going gets hot. Around here, it can go from -35*C to almost +20*C (~70*F). between morning and mid-afternoon.

[archtop]

If it were me and price was the same and it was easy to get, I would run 5W40 year round. You may have "hot" days during the winter and the 40 wt will provide a bit better protection when the going gets hot. Around here, it can go from -35*C to almost +20*C (~70*F). between morning and mid-afternoon.

Thanks Xviper ,ordering a case of 5-40 today. :rockon: