Hi, can you please advise capacity for n20 engine for 2014 BMW 428i Xdrive coupe?

~8L total capacity across engine/radiator.

I have a 2023 bmw m340i xdrive is this suitable?

Your vehicle should be filled from the factory with HT12.

I have a 2012 BMW X5 35d w/ a 3.0L diesel engine and I am going to be replacing my thermostat. I was thinking that I might as well perform a coolant flush on my vehicle since it's been 100K since my last coolant flush. How many gallons do I need?

The entire system is 11 quarts, although you will not be able to get all of it out, so between 1-2 gallons should do it since it's concentrated.

08 335i E90 N54, if I am replacing basically everything in the coolant system, IE: expansion tank, all hoses, including lower coolant return hose, so how much coolant do I need?

The entire system would hold just about 9 quarts or 8.5 liters.

Hello, Is this coolant (82141467704) suitable for BMW 525IA E34 (year 1994) ?

Yes.

Would I need 5.5 mixed with 5.5 distilled water for a 50/50 ratio for a 2013 Xd 3.5D?

Yes correct

How many gallons does it take to fill.. a bmw 328i 2009?

The total system capacity is around 10 liters on an empty system (includes heating circuit). One gallon of this concentrated antifreeze when mixed with distilled water makes 7.57 liters of coolant. This will be more than sufficient to fill your cooling system after repair work as there is always leftover coolant in the cooling system.

Is the this coolant part of the lifetime warranty?

Yes.

What happen if I don’t mix this coolant and just put it in just as it is ?

Coolant by itself is highly concentrated and highly corrosive. Without diluting coolant concentrate, it will corrode your vehicle's coolant hoses/lines which can cause further damage in the future. Genuine BMW coolant needs to be diluted as per the instructions on the back of the bottle.

How many of these gallons should i need when bleeding and refilling 08’ BMW N54 335i?

e9x 335i Engine Coolant Capacity is 9 Liters so 2.377 Gallons accordingly.