I just did a search on this site and then one using the "AI wizard." Two days ago, I completed a brake fluid change on my 1975 CSi. I had a can of ATE "blue" DOT 4 on hand and used that. Then, I wondered if this 51 year old car had any special brake fluid requirments other than using nothing less than DOT 3. I found nothing here but the AI wizard recommended against using a modern DOT 4 fluid due to the lower viscosity of the ATE. Nothing about damaging the brake system was mentioned. So E9 wizards... is ATE DOT 4 safe if not overkill?