We commonly field questions regarding brake fluid. Brake fluid comes in 4 flavors; Dept of Transportation DOT 3, 4, 5.1, & 5. You can mix & match Dot 3,4 &5.1 [glycol based]. Dot 2 went away in the '60's. Some are concerned because the old familiar brands have changed. Castrol LMA now says “Synthetic” on the bottle. The Lockheed “Premium” fluid has been replaced by “Super DOT 4.” Others have questions about the ever-contentious silicone brake fluid. Dot 5 is not for the price conscious, it's super expensive. As an aside, lots of the modern cars come with Dot 4 brake fluid. Dot 4 is a glycol/borate mix that raises the boiling temp to a whopping 446 degrees. Dot 5 cannot be used in modern cars, it messes up the ABS systems [foaming up]. The only thing DOT 5 mixes with , is, well Dot 5.
When it comes to picking a brake fluid for your DeTomaso, do not consider anything that doesn’t meet FMVSS 116. Fluids rated at DOT 3, 4 and 5.1 are all hygroscopic, meaning they will absorb water out of the atmosphere. This will lower the boiling point of the fluid. The presence of water eats away at pistons & calipers. We recommend using fluids that meet the DOT 4 specifications, like Castrol GT LMA and the Lockheed Super DOT 4. Super Dot 4 will run you about 45 bucks for 5 liters.
A common misunderstanding is that DOT 5.1 fluids are connected to DOT 5 fluids. This is not true. Think of 5.1 as a glycol-based DOT 4 fluid that meets DOT 5 standards. The 5.1 fluids are used primarily in vehicles equipped with ABS. If you choose glycol fluids, they must be completely drained and replaced every 18 to 24 months, regardless of how much you drive your car. Glycol fluids will strip the paint off the car if they spill or leak.