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NickZee · 09-02-2015, 07:22 PM

Hi everyone,

New to the forum, have been hypermiling a 2014 BMW 640i Gran Coupe. Although it is a fantastic sports car, it also has a fantastic Eco Mode that is very effective and and fun to use because of all the data that it provides to the driver. I see hypermiling more as an Eco-friendly challenge that avoids a few stops at the gas station as opposed to any real concern about saving money.

The manual States that 95RON fuel is recommended, and the minimum requirement is 91RON. Any lower than 91 may cause damage according to the manual. So 91 should be safe to use and on my first tank I have not noticed any problems with the smooth running of the engine.

I was wondering if any of you could chip in about whether using below recommended rated fuel is likely to effect mileage when driving at low to moderate loads?

If there is no knocking at low to moderate loads, and the energy rating of 91 is the same, then I should be able to use 91 without adverse effect on mileage?

91 is generally 9% cheaper than 95, and my limited driving so far indicates that fuel economy is about the same on my work run but it is early days in this experiment.

09-02-2015, 07:22 PM	#1 (permalink)
NickZee EcoModding Lurker Join Date: Sep 2015 Location: Melbourne Posts: 2 Thanks: 0 Thanked 0 Times in 0 Posts	91RON in car optimised for 95RON fuel Hi everyone, New to the forum, have been hypermiling a 2014 BMW 640i Gran Coupe. Although it is a fantastic sports car, it also has a fantastic Eco Mode that is very effective and and fun to use because of all the data that it provides to the driver. I see hypermiling more as an Eco-friendly challenge that avoids a few stops at the gas station as opposed to any real concern about saving money. The manual States that 95RON fuel is recommended, and the minimum requirement is 91RON. Any lower than 91 may cause damage according to the manual. So 91 should be safe to use and on my first tank I have not noticed any problems with the smooth running of the engine. I was wondering if any of you could chip in about whether using below recommended rated fuel is likely to effect mileage when driving at low to moderate loads? If there is no knocking at low to moderate loads, and the energy rating of 91 is the same, then I should be able to use 91 without adverse effect on mileage? 91 is generally 9% cheaper than 95, and my limited driving so far indicates that fuel economy is about the same on my work run but it is early days in this experiment.