Originally Posted By Scrambledsignals
I wonder if there is an element of "Emperors' new clothes" about using higher octane fuel in cars with modern engines.

There was a comprehensive test done on the higher grade fuels on one of the motoring programmes (fifth gear I think) a couple of years ago.

Have a look at the programme excerpt on youtube

https://www.youtube.com/watch?v=d8L-X89duEs

The improvement in performance from the best of them was at best marginal and some showed no difference.

Results on older engines might of course be different

Totally agree. I had an Uncle who insisted on using the "best" fuel available so always filled with 101 octane later known as 5 star despite owning a string of mundane vehicles.

Having said that I did use the recommended 5 star in my CV8 (10.5:1 C/R) back in the 70's and when it was available. Also currently use premium unleaded in my Velocette to avoid pinking.

I had heard that you may get slightly better mpg with premium unleaded on some modern engines, but the improvement is not commensurate with the substantially higher price.

Last edited by Richard Wood; 03/02/19 11:31 AM.
Richard

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