kmd1154 Posted October 4, 2015 Share Posted October 4, 2015 With the weather forecast suggesting that today would be the last of the sunny days for a while I was keen to get the weekend chores out of the way so I could get the little car out for an hour. Our Lass requested milk and diet coke (she always drinks it if she has a hangover !) so Tesco in Catterick Garrison was first up, together with a refill. Now, with my bikes (BMW's) the suggestion in the owners manual is that while they tolerate all manner of inferior fuels, they thrive on higher octane stuff. So I decided to give the Westy a tank of 99 super unleaded, just to see. Seems to like it ! Runs smoother, cleaner, and more willing to rev/pull. I know my bikes run cooler on the high octane stuff but I couldn't tell with the Westy. But I'm sure it wasn't rose coloured glasses, performance was definitely up. Anyone have any experiences they'd like to chip in with ? Quote Link to comment Share on other sites More sharing options...
dombanks Posted October 4, 2015 Share Posted October 4, 2015 Someone get the popcorn out. I've got some beers it's another 99octane super plus fuel thread lol If it was a noticeable difference and given the lack of relevant sensors to adjust the ecu I would hazard a guess your car was tuned on 98/99 octane rather than 95 in the past. Interestingly I have found my z4 runs much smoother on tesco99 Ron monentum but I was getting 5mpg lower than shell 98 optimax. Normal 95 Ron shell was about the same as the momentum but with much more pinking. Sainsburys high octane stuff was low on consumption and ram like a bag of spanners. Nothing scientific on the test I just ran the car in the same journeys for 2 months on each fuel using about a tank a week. Currently run high octane stuff from Costco Cos it's only 108.9 1 Quote Link to comment Share on other sites More sharing options...
DanDud Posted October 4, 2015 Share Posted October 4, 2015 Supermarket fuel is produced to a lower standard than branded fuels (i have asked different fuel reps) and now all regular unleaded contains ethanol, the percentage is different depending what refinery it came from. Most of the high octane stuff doesn't contain ethanol. Several years ago we tested a branded fuel v's Tesco own brand in a very basic, non scientific way (regular unleaded). The car in question was only used to and from work and would be driven in the same manner (by the same person) throughout the test. the test went like this... filled up twice with branded to purge out any other fuel that might have been in the tank, then 3 tankfuls of the branded fuel, using the low fuel light to tell the driver to fill up (there's approx 1.5 ltr in it at that point), then did the same with the supermarket fuel. Unfortunately i cannot remember the exact consumption figures but there was a significant difference and the car ran better on the branded fuel. Quote Link to comment Share on other sites More sharing options...
dombanks Posted October 4, 2015 Share Posted October 4, 2015 I would be very surprised at it being made to a "lower standard" more like the additive package mixed into the the base fuel will be different. Fuel is made to a specific standard BS en 228:2012 look on the pump next time you fill up. Quote Link to comment Share on other sites More sharing options...
DanDud Posted October 4, 2015 Share Posted October 4, 2015 Ok if you want to be pedantic, yes it's the additive package that isn't there. I will be more specific in future. Quote Link to comment Share on other sites More sharing options...
TAFKARM Posted October 5, 2015 Share Posted October 5, 2015 You're both right of course. Base fuel is all required to meaet the minimum spec and it's the additive that makes the difference. Of course, you could dispense with ground fuels completely and run AVGAS... Quote Link to comment Share on other sites More sharing options...
Welly Jen Posted October 5, 2015 Share Posted October 5, 2015 Could also be the high atmospheric pressure over the weekend. High pressure and cool temperatures mean more air getting to the engine. Fuel injected cars with the appropriate sensors have more power on cold high pressure days. Maybe the set up on your cross flow carbs like it too. Jen Quote Link to comment Share on other sites More sharing options...
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