Automotive fluid(s) you swear by for your car

[SayChiSinLo]

Here's how I'm thinking we can make this work:

Year: 2009
Car: Mazda Mazdaspeed 3
Motor Oil: Pennzoil Platnium 5w30
Transmission Oil: Ford Motorcraft XT-M5-QS with half a bottle of Ford Motorcraft XL-3 Friction Modifier

Why this motor oil: For my car, it's really a toss up between Pennzoil Platnium and Rotella T6 as the best motor oil for the car. In this case, I really go by the forums because they claim these oils are the two best for this car. There are lab tests showing that the Pennzoil Platnium and Rotella T6 simply wear better for my motor. I found Pennzoil Platnium first, and I've stuck with it ever since. I usually change my motor oil every 5000 miles, but I have stretched it to 7000-8000 miles and it holds up well. Note: some people have gone to a thicker 5w-40 if they experience issues with their turbo seals.

Why this transmission oil: Ford Motorcraft XT-M5-QS is unanimously liked across ALL Mazdaspeed 3 owners. Many people have called this transmission oil as "honey". It's worlds better than my factory oil. The shifts are much smoother with this fluid. I am now at 35,000 miles on this oil and I am certainly at the upper limit of its life. But you know what? I don't notice any degradation in shifting at 35,000 miles. BUT that doesn't mean I'm going to push my luck. I'm changing the fluid as soon as they come in the mail. I am also using the Ford Motorcraft XL-3 Friction Modifier for my LSD. Supposedly, Ford Motorcraft "honey" lacks the additive to ensure smooth LSD operation.
No additive = noisy/whiny LSD operation.
Full bottle of additive = stiffens up shifting, some people like it, some people don't.
Half a bottle of additive = Sweet spot for me.

 

[motortrend]

Year: 2001
Car: BMW M5
Motor Oil: Castrol 10W-60
Transmission Oil: Have yet to change the trans. oil

Why this motor oil: There are very long threads on M5board on what oil to use as well as on M3post, you can read all of them and take what you will from them but I trust what my mechanic says and the choices BMW made. As my mechanic tells me when he used to work at the dealership (early 2000s) cars had bearing troubles on the S62 and S54 and actually on the engine bay it says to use 5W-30 (This is before the 10W-60) so BMW got together with castrol to develop this for the M engines and they started using it at dealerships with good results. Currently the E92 M3 (Which also uses 10W60) is going through the same troubles and people changing to other brands and viscocities such as 0W-40 in winter time. Since there are never cold temps here and I don't go over 3K until the lights are gone and don't go over 4K until the needle is close to the middle I believe 10W60 is the best choice and that people with bearing problems are either putting too much stress on the car with modifications that involve boost or driving them too hard when the oil has not yet reached operating temps.

Why this transmission oil: N/A