[digisky]

Factory oil, you’ll need three bottles. Expensive.

Genuine Smart 001989510310 ATF, Automatic Transmission Fluid; Synthetic 75W-90 - Smart | 0019895103 BOT328

Find Genuine Smart ATF, Automatic Transmission Fluid; Synthetic 75W-90 001989510310 at discount prices in our extensive Smart auto parts catalog. AutohausAZ offers a large selection of Genuine Smart parts online. Fits Smart Fortwo. 0019895103 BOT328

www.autohausaz.com

 

[digisky]

Here is one that is not approved of course, but is GL4 and a synthetic:

Ultra1Plus™ SAE 75W-90 Synthetic Gear Oil, API GL-4 https://a.co/d/dflAvjj

 

[digisky]

Valvoline SynPower 75w-90 Is not good, it is GL5

 

[digisky]

It’s not friendly for the synchronized transmissions.
Here is a direct quote from Valvoline:

“Recommended for conventional and limited slip differentials and non-synchronized manual transmissions where API GL-5 or API GL-4 fluid is specificed”