jadnashuanh
Posts: 4766
Joined: Thu May 22, 2014 2:07 pm
Location: Nashua, NH USA

Re: Does the rex required regular or premium fuel?

Sun Feb 21, 2016 7:04 pm

Higher octane fuel contains more additives, which, in addition to raising the octane level, helps keep things cleaner by their detergent actions. But, in general, using a higher octane fuel than the engine was designed for doesn't really pay you much as opposed to too low of an octane rating which can damage an engine. If you're lucky, you can buy gasoline without added ethanol, but there are a number of states where that is impossible. Ethanol lowers the energy content per volume, meaning that you'll take a hit on fuel economy. And, because ethanol has an affinity for moisture, an open system (the REx's is closed), can be a problem.
Jim DeBruycker
2011 535i x-drive GT, 2014 i3 BEV

imolazhp
Posts: 244
Joined: Sat Mar 28, 2015 8:02 pm

Re: Does the rex required regular or premium fuel?

Sun Feb 21, 2016 8:54 pm

I may not have any DCFC's within 3 hours of me but I do have a non ethanol station near me.

MarkN
Posts: 89
Joined: Thu Oct 31, 2013 12:45 pm
Location: Fort Collins, CO USA

Re: Does the rex required regular or premium fuel?

Wed May 04, 2016 1:24 pm

Two days ago the range extender on our 2015 i3 refused to turn on and the battery died two blocks from our house. We got the car back this morning. It had had five different error codes, one of which was for an engine misfire. Our service advisor said that BMW is now recommending 87 octane gasoline for i3s used at high altitude like in Colorado to prevent misfires. Apparently lots of REx owners in Colorado are reporting misfires. In November misfires illuminated our check-engine light.
2015 i3 REx

alohart
Posts: 1857
Joined: Sat Nov 01, 2014 7:36 pm
Location: Honolulu, HI

Re: Does the rex required regular or premium fuel?

Thu May 05, 2016 3:17 am

MarkN wrote:Apparently lots of REx owners in Colorado are reporting misfires. In November misfires illuminated our check-engine light.
It's amazing to me that a low-output engine running at relatively low speeds would suffer from misfires. Does a similar engine in a BMW scooter suffer from misfires? It probably does but doesn't run under such stringent emission requirements that probably require that misfires set diagnostic trouble codes.
Aloha,
Art

2014 BMW i3 Arravani Grey, Giga World, Tech + Driving Assist, Parking Assist, DC Fast Charging, JuiceBox EVSE

jadnashuanh
Posts: 4766
Joined: Thu May 22, 2014 2:07 pm
Location: Nashua, NH USA

Re: Does the rex required regular or premium fuel?

Thu May 05, 2016 1:53 pm

While higher altitude lessens the need for premium fuel (unless you have a turbo), I'm not sure why that is related to misfiring if used. I wonder if, because the fuel in the REx may be old from non-use, that people may have 'winter' fuel in it still once it warms up, verses 'summer' blended fuel when actually needed or vice-versa. Might be a good practice to just run the REx's tank dry (well, as dry as the computer will let you!) periodically, and refilling with fresh stock might help. 'Summer' blended fuel has less volatility, and might be harder to ignite if it's cold out.
Jim DeBruycker
2011 535i x-drive GT, 2014 i3 BEV

MarkN
Posts: 89
Joined: Thu Oct 31, 2013 12:45 pm
Location: Fort Collins, CO USA

Re: Does the rex required regular or premium fuel?

Thu May 05, 2016 3:13 pm

jadnashuanh wrote:While higher altitude lessens the need for premium fuel (unless you have a turbo), I'm not sure why that is related to misfiring if used. I wonder if, because the fuel in the REx may be old from non-use, that people may have 'winter' fuel in it still once it warms up, verses 'summer' blended fuel when actually needed or vice-versa. Might be a good practice to just run the REx's tank dry (well, as dry as the computer will let you!) periodically, and refilling with fresh stock might help. 'Summer' blended fuel has less volatility, and might be harder to ignite if it's cold out.
At least in my case old/non-seasonal fuel shouldn't be the problem. I drive our i3 on a 110-mile trip once a week and need to re-fuel every 2 to 3 weeks.
2015 i3 REx

bwilson4web
Posts: 745
Joined: Fri Apr 29, 2016 11:59 pm
Location: Huntsville, AL

Re: Does the rex required regular or premium fuel?

Sat May 14, 2016 9:39 pm

Having gotten a copy of the Owner's Manual, they list 89 as the lowest allowable. This makes sense as in the i3, the engine HP is listed at 34 hp compared to +60hp in the motor scooter. But I'd rather get some metrics before doing any extensive operation below 89.

Near as I can tell, the engine lacks a knock sensor that would allow the controller to handle lower octane fuel. But 89 (aka., plus) makes sense.

Bob Wilson
20k/27k mi 2014 BMW i3-REx
10k/10k mi 2017 Prius Prime

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