Which fuel (UK) for 4.8is? E10 ok?
 

Hi All

I did search but whilst there is plenty of discussion about RON I couldn't find an answer to the question I had, can the 4.8is run on E10 fuel?

I couldn't get a conclusive answer so filled up with RON 99 E5 instead but at the moment that's an extra 20p/litre! and with the crazy high fuel prices if the fuel lines and engine are compatible with E10 I'm inclined to use it.

Thoughts?

No, don't use it.

It's not that it's bad for the engine but many hoses, seals and gaskets degrade when exposed to ethanol and vehicles made for flex fuel have revamped seals, gaskets etc.

I have a Euro spec 4.8iS and almost always run 95 with the occasional 91 (lowest available here)

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You can't even get E0 where I live anymore, unless you buy "clear premium" which is usually$1/gal more expensive than normal premium. So my car has been running on it for the last ten years or more exclusively. I don't know what would be different about the 4.8iS and I imagine that most US 4.8s have been likewise ran on E10 for many years now.

US gas is basically all E10. No reason not to run E10. I would not be running 91 RON fuel unless there was no choice.

Folks keep getting confused by this, but US AKI octane is different from RoW RON octane. Roughly speaking, US octane is about 4 points lower for the same gas. 87 AKI is about the same as 91 RON. 93 AKI is 97/98 RON.

Net-net, I would try to run at least 91 AKI / 95 RON fuel. I wouldn't worry about E10.

The two big issues with E10 that I've seen are:
1) octane loss in storage. the ethanol can separate from the fuel over time.
2) switching from non-ethanol to ethanol gas can be a problem if you've built up a bunch of water in your fuel tank. ethanol is hygroscopic, whereas regular gas is not.

I’ve been running E85 for two years now.

Winter blends have E15, and summer blends are E10. It’s a matter of running lean. If you have higher ethanol levels like E15, on days like today in California where the forecasted high is 107 degrees, you are definitely going to be running hotter because of how oxygenated the fuel is.

The DME is not designed to run high level ethanol fuels, so there is only so much it can adjust. During the winter season, the cooler temps generally help with avoiding lean conditions, so E15 shouldn’t be an issue. Ambient temperatures definitely play a role in the fuel trims between E10, and E15 for a standard DME.

Ultimately a high level ethanol fuel like E85 is better for heat. But, the vehicle must have a flex fuel system to adjust the fuel trim to an appropriate mixture. This is the only way to avoid lean conditions.

I personally avoid unleaded fuel, ethanol is a superior fuel.

For those worried about ethanol affects, check the link below out.

https://lucasoil.com/products/fuel-t...th-stabilizers

Thanks for all the inputs. Sounds like I’m fine to use RON 95 E10 then.

Here’s some info from BMW:

http://www.bimmerboard.com/members/q...ex%20Fuels.jpg

Thanks that’s helpful.

It’s interesting that BMW state for furs up to 10% it won’t invalidate warranty ( to relevant in my case anyway) but may cause issues in driving.

I might well be imagining it, most likely am to be honest, but I swear the X felt immediately more responsive on he throttle after I brimmed the tank with RON 99 the other day. I have checked with my dad who I got the car from and he had just been using RON95 E10.

The DME probably threw a bit more timing at the system, due to the higher octane fuel.

Around two decades ago, on roadfly, some guys strapped an E46 M3 to a dyno and dyno tested different octant blends.

What they found was that the S54 with a *stock* tune would make more power up to 96 octane, IIRC. Note that that's US AKI octane. That'd be 100-101 RON how it's measured elsewhere. Now, the S54 is more high strung than most engines, but I'd expect even average BMW engines like the N62 to pull timing on 95RON.