75W80 diff oil
 

I found Lucas 75W90 on sale for 11.00 a quart. ( Pepboys) Cheaper than anything else ECS tuning has. ( liquid moly) my understanding that even though it has friction modifies. Which the highly recommended Redline does. That it should be fine for use in a open diff like our E70s?

https://www.pepboys.com/lucas-oil-75...roduct/9166888

I would pass on the Lucas 75W-80 and use a better oil. OEM oil is 75W-90 synthetic (BMW SAF-XO). Consider running a quality 75W-90 synthetic from Redline, Valvoline, Castrol, or Mobil 1.

Also, there is no issue running a gear oil with friction modifiers in an open differential.

Edit: looks like the 75W-80 was a typo in your post title. Regardless, the Lucas is considered lower tier. If you want to buy at an auto parts store, go with Mobil 1 or Valvoline.

Understood. I mispoke, i mean't to say 75W90. In the past i've used Valvoline Syn power. Sounds like you'd recommend that over Lucas then.

No worries. I use Redline in everything I own, as do many BMW owners. I think their product is better than just about anything else on the market. But it’s a bit expensive at $18 a quart.

FYI, you will need 2 quarts to do both differentials. You’ll be able to suck about 1.1 quarts out of the rear differential, and the front differential takes about 0.7 quarts. I just did both last weekend.