[F10_User]

As we all know gas prices are up the roof, do you all still put the recommended 89 min (premium) on your vehicles?

[Boardmember]

In my state, choices are 87, 89 and 93. 93 comes at a minimum $.70/gal premium, frequently more. Yes. Every time.

[nZtiZia]

I use Premium 93 in my 45e given I don’t refuel as much. 89 is considered Plus where I live, and I wouldn’t hesitate to fill up with it if my situation were different

[Gene Horr]

In general, for modern vehicles driving in a moderate manner using a lower octane than requited does not physically hurt anything. The computer will retard the timing to prevent detonation (sometime called 'knocks and pings' because that is less scary sounding) and dieseling isn't an issue with electronic fuel injection.

But you probably aren't saving much money. The retardation lowers the fuel economy, reducing or sometimes eliminating the per gallon cost savings. And if living in a high heat climate, or really pressing on the throttle, then you are not only reducing efficiency even more you might exceed the capability of the systems to compensate.

Personally, I wouldn't unless it is cool weather and you plan on driving slow and cautious.

[MassWholeBimmer]

I put 93 in. Big $ jump from 87 to 89. Not so much from 89 to 93. So 93 it is.

Side note: My F150 requires a min of 87. I've put in 93 and never really noticed much difference. I think the 3.5 HO (Raptor f150) requires premium.

[Gene Horr]

Originally Posted by MassWholeBimmer

Side note: My F150 requires a min of 87. I've put in 93 and never really noticed much difference.

This is normal. Lower compression engines get no benefit from higher octane fuel and a case could be made that there is a negative due to less energy/gallon.

[weinerbarn]

X5MC gets 93 every time but I also do not drive it much. Less than 3,000 miles per year. Other vehicles, all turbo will get 93 most times but if I'm going on a long road trip, not towing and just planning on cruising and burning fuel, then I will put mid (89) in since I know I'm not going to be in much boost and no need for higher octane. The cost savings adds up over a 1-2K mile round trip.

[cobramite]

Originally Posted by weinerbarn

X5MC gets 93 every time but I also do not drive it much. Less than 3,000 miles per year. Other vehicles, all turbo will get 93 most times but if I'm going on a long road trip, not towing and just planning on cruising and burning fuel, then I will put mid (89) in since I know I'm not going to be in much boost and no need for higher octane. The cost savings adds up over a 1-2K mile round trip.

You then need to run down to near empty when you refill with 93 octane. Not worth it for 25 bucks.
Don't be the guy with a $150,000 911 filling up with Sam's club penny pincher mystery gas.

[weinerbarn]

Originally Posted by cobramite

You then need to run down to near empty when you refill with 93 octane. Not worth it for 25 bucks.
Don't be the guy with a $150,000 911 filling up with Sam's club penny pincher mystery gas.

Ha ... fair point. I've actually never filled my X5MC up with anything but 93 but the other cars like 540i, I don't really care enough about to worry. But you are correct, $4 per tank isn't making car payments and if you're that tight, you probably bought the wrong vehicle.

[2heeldrive]

I worry about LSPI (Low Speed Pre-Ignition) which is very bad for pistons/rings/plugs etc. and is a function of octane and oil vapors. I don't think timing is much of a factor. So I run 93 octane which is the highest I can find around here.

This is pretty good explanation of LSPI:

https://www.valvolineglobal.com/en-eur/what-is-lspi/

[LDT]

93 all the time. Costco sells only top tier fuel and is always the lowest price.

[christianb5s4]

91 octane only on our x40i. Not worth cheaping out on fuel in my opinion, despite the cost difference.

[HowardThings]

I use 89 frequently.. (40i)

Initially it was an accident but I took the opportunity to do some logs monitoring knock, boost, and timing corrections.

Findings: it’s barely noticeable. DME adjusted boost to build up a little later but it was perfectly fine otherwise. WOT pulls were okay as well even with IATs getting as high as 130 degrees. I get about 500 miles to the tank with easy driving. With a difference of $12.00 a tank, I only justified it since I drive about 30k miles a year with A LOT of idling in between. I just don’t see the point of it unless I’m beating on it with my jb4 set to map 3 or just take the race car out. I don’t see a problem using 89 for a commuter car.

Now this is on a completely stock car with stock tune (jb4 map 0). I would NOT recommend anyone running a tune if any sort running under 91/93 octane.

[hyperion69]

Originally Posted by christianb5s4

91 octane only on our x40i. Not worth cheaping out on fuel in my opinion, despite the cost difference.

Exactly... Cheaping out on fuel with a premium car is madness. In Europe, we pay ~ 5-6$ / gallon (octane 95/98)