Hi, I have a 1990 Ford Thunderbird Supercoupe.  It's a 3.8 supercharged with a lentech built transmissions.  It has a bigger mpx supercharger with a bigger front mount intercooler.It is 25% overdrive on supercharger  and has 85mm tb and mass air. It has ported heads and intake. It has a cam ,60lb injectors methanol injected ,bigger exaust, headers and tuned with a chip.Im probably forgetting something...

This car has run on mobile 1 15W-50 since ive owned the car and since the engine was built im sure. The manual for my car says 5W-30. Should I be switching back to 5W=30 or keep running 15W=50? The car seems fine with 15W-50 but I don't want to do any damage . Can I get you opinion please? I have been running it for about 6 years like this...summer only.

Thanks