Talk Morgan Forums Community The Malvern Arms Is it worth using super unleaded in a Plus 4?

Does he work for Shell 🙈

Yes its worth it.

The Morgan runs sweeter on it. My VW Up! doesn't wimp out on hills with high octane juice and the Cooper S handbook states for best performance 99 octane is recommended.

Its likely more economical as well so extra cost is probably covered as well.

Some might argue it doesn’t matter what you fill up with and from whom but another friend imports American Classic cars and the first thing he has to do with many of his cars is completely replace the fuel tank and fuel system because the quality of fuel in the USA was poor in many filling stations with poor storage that allowed water to get in the fuel

No he’s an architect who works for several of the forecourt operators which aren’t the fuel companies themselves

I was informed by the head mechanic at Kia Linwood never to fill up the Sedona with Morrisons diesel.

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

When I do the dyno setup for the ECU I run standard fuel on the basis that it's safer if for any reason can't get super.

My tuner has told me that for a moderately tuned engine, the power gains to be obtained from super are minimal provided the fuel and ignition are properly tuned for the standard petrol grade.

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.

Is that because your car has a petrol engine?

I remember Fifth Gear doing tests on additives and no real benefits.
I used Millers in my Focus turbo diesel and it did improve mpg, basedon long term comparisons. A mate tried it in his Golf and had no benefits. A bottle cost £11 and lasted several tankfulls. Over the life of the bottle I saved £36 so net saving of £25. Commute was main mileage...100 miles daily mainly M4.
For my Plus 8 I used V-Power as it does work. With 95octane I was getting MIL light coming on for “random intermittent misfie” detection although the engine seemed ok. V-Power has stopped it. It has come back after filling with 95 once, when, on leaving the petrol station, I accelerated hard. Mpg? I compared 95 v V-Power and was getting 30 (95octane) and last test showed 31 (V-Power) so no real benefit there. I don’t feel any improvement in performance so if it is there it is small.
I have the Rover V8 with Gems management, Magnecor leads and plugs are good.
In the end it depends on the engine, tune, ecu set up. An occasional use of higher octane/extra cleaner/lower ethanol may help but that is your choice. Fir me it is ok and the extra cost not excessive.

aerotaf...where are you?
Em..tell them about your boat outboard....