Does anyone run mid-grade fuel in their Cooper S Paceman? The gas filler lid says that I can, but I haven't yet. Mileage or power effects?

 

There are a number of threads on this site about fuel usage. I'd suggest you stick with premium.

 

Copy that. Thanks.

 

concur that you read up and decide for yourself

I'd suggest beginning with figuring out what "octane" means. Hint, there is a connection between 'compression' and octane. A turbo's purpose is to increase compression.

short answer is today's engines are smart enuf to sense what octane you have put in and adjust the fuel/air/ignition so you won't damage anything (up to a point). If you use a lower octane than what's recommended you will loose a little power ... and for the most part if you run higher you just waste money

My current daily driver is also a 2 liter 4 cyl turbo and in the owner's manual they give chart of the HP and torq' for various commonly available fuels .... top to bottom is only a couple of HP . . .

I recently posted this link: https://grassrootsmotorsports.com/articles/fuel-truth/

*******
btw .. my 79 calls for 93 octane or better. I once filled with 89 .... this car does not have computers to adjust automatically. I have NEVER NEVER made that mistake again! It would hardly hold an idle, kicked and bucked under load - aka 'pre-ignition knock - and would run after the ignition was turned off (- also pre-ignition ... "dieseling")