im also running penrite hpr15 in the vct engine with the supercharger..
the thing i find is its still good on fuel considering its supercharged..
its actually better on fuel than my eb ghia..lol.

so changing to a lower viscosity will improve economy??.. hmmm interesting!!

ive been told to stay clear of penrite. for the money you pay its not as good. passing on what my mechanic said to me. i was using penrite now am off it. its boiling point is alot lower than other oils. aswell as its crystallizing point is also alot lower. one of his customers blew his turbo because it blocked the turbo line.

ive been using penrite for over 10 years and never had issues..i change my oil every 5000km and the engines are always clean internally and always have good oil pressure.. so i cant complain!!

the mechanics customer blew his turbo probably because they didnt clean the filter in the oil line when it was serviced...

actually the flash point or the penrite oil is higher than the shell helix and castrol magnatec..
there are other oils but these are the only ones i tech sheets for...