[saudisinaudis]

I am considering buying MS109, and mixing it with the station 91 fuel occasionally whenever thinking of doing pulls /rolls in order to achieve better performance, and not having the car slightly underperform. Better fuel is always better.

Alternatively, I'm thinking of an E25 blend on the 91 fuel, which is cheaper than buying race. Does anyone do that?

[ChrisM4]

MS109 unleaded will have zero issues mixed with 91 to get to 93. Just give it enough time for the gas to mix. I can’t help on the E question though.

[TopJimmy]

Ethanol is a better octane booster and cheaper than MS109.

Mix:
12gal 91 octane E10 pump gas
+ 3gal of E85 pump flex fuel
= E25 at 93 octane
Easy peasy!!!

Alternate is 1gal of MS109 fuel into 12gal of 91 pump to yield 92.4 octane mix. 1gal of MS109 costs about $20+

Remember at — — on your fuel gauge you should have exactly 1 gallon in your tank. Account for that in your mixing.

[saudisinaudis]

Originally Posted by TopJimmy

Remember at — — on your fuel gauge you should have exactly 1 gallon in your tank. Account for that in your mixing.

I don't get, what is — — on my fuel gauge? I got the calculations but have no idea how to measure how many liters of fuel my tank is at. I don't trust the gauge and my eyestimation to accurately reflect that.

[saudisinaudis]

TopJimmy
Would I be ok using a X98 blend of ethanol as it is cheaper than X85? 5 gallons of X85 costs $55, X98 costs $51 and I'd use less of it to acheive the desired octane rating.

So here was my calculation: On 1.5 ticks on the gauge cluster (with each tick representing 10 liters from what I read), which is 1/4 of the tank filled with 91, I should add exactly 5 liters of X98 to achieve a final rating of E25 / 93 octane. Correct?

[TopJimmy]

Originally Posted by saudisinaudis

I don't get, what is — — on my fuel gauge? I got the calculations but have no idea how to measure how many liters of fuel my tank is at. I don't trust the gauge and my eyestimation to accurately reflect that.

The double hyphen is what you will see in place of the Distance To Empty number on your dashboard. When the symbol first appears you have 4 liters in your tank.

[TopJimmy]

Originally Posted by saudisinaudis

TopJimmy
Would I be ok using a X98 blend of ethanol as it is cheaper than X85? 5 gallons of X85 costs $55, X98 costs $51 and I'd use less of it to acheive the desired octane rating.

So here was my calculation: On 1.5 ticks on the gauge cluster (with each tick representing 10 liters from what I read), which is 1/4 of the tank filled with 91, I should add exactly 5 liters of X98 to achieve a final rating of E25 / 93 octane. Correct?

I use VP X98 for the same reasons, and I know it’s 98% so my final mix is more accurate.

40 liters of pump 91 gas plus 6 liters of X98 gives 93.6 octane at 21.5% ethanol.
If you used 8 liters instead of 6 you get 94.3 octane at 24.7% ethanol.

[BEAR-AvHistory-2]

You don't need to be that precise. 94 95 whatever is not going to hurt your engine. Engine will only use the octane it needs.

Don't bother with my current cars but have been a mixer going back to a 2011 335is 7DCT.

Car used either a mix of 93 our standard premium & 100 out of the pump race gas. Alternative was a mix of 93 & E85. Would not go over 30/35% with E85. Car as the content goes up starts to need additional equipment like better fuel pumps etc.

I liked to run around 95 octane when stock as dynos indicated some overhead capacity to increase power above what 93 would give.

At 95 there were no more gains till the cars were tuned.

[TopJimmy]

Originally Posted by BEAR-AvHistory-2

You don't need to be that precise. 94 95 whatever is not going to hurt your engine. Engine will only use the octane it needs.

Don't bother with my current cars but have been a mixer going back to a 2011 335is 7DCT.

Car used either a mix of 93 our standard premium & 100 out of the pump race gas. Alternative was a mix of 93 & E85.

I liked to run around 95 octane when stock as dynos indicated some overhead capacity to increase power above what 93 would give.

At 95 there were no more gains till the cars were tuned.

His alcohol is $5 a liter so best to be precise and not waste any. I use 1.5gal X98 into 10gal of pump 93 to get my 95 octane at 20% E.

[saudisinaudis]

Originally Posted by TopJimmy

His alcohol is $5 a liter so best to be precise and not waste any. I use 1.5gal X98 into 10gal of pump 93 to get my 95 octane at 20% E.

That’s because your pump has 10% ethanol already, right?
Our fuel in Saudi reportedly has 0% ethanol.
So I would only need 1.5 liters of X98 over 15 liters of 91 pump to achieve 93 octane, and I would be at 9% ethanol.
At 40 liters of pump, I’d need 5 liters of X98 to achieve 93.8. I’d be at 12.5 ethanol then.

If I went for E25 total concentration, I’d peak at 96 octane, which is overkill imo. Pump ethanol concentration changes everything…

[TopJimmy]

Originally Posted by saudisinaudis

That’s because your pump has 10% ethanol already, right?
Our fuel in Saudi reportedly has 0% ethanol.
So I would only need 1.5 liters of X98 over 15 liters of 91 pump to achieve 93 octane, and I would be at 9% ethanol.
At 40 liters of pump, I’d need 5 liters of X98 to achieve 93.8. I’d be at 12.5 ethanol then.

If I went for E25 total concentration, I’d peak at 96 octane, which is overkill imo. Pump ethanol concentration changes everything…

I didn’t realize you had “pure petrol” in your region. I’ve recalculated below starting with 10 liters of 91 octane all petrol, and adding VP X98 in liters.

10 liters 91 octane all-petrol
+1 liter X98 = 92.8o 8.9E%
+1.5 liter X98 = 93.6o 12.8E%
+2 liter X98 = 94.3o 16.3E%
+2.5 liter X98 = 95.0o 19.6E%
+3 liter X98 = 95.6o 22.6E%
+3.5 liter X98 = 96.2o 25.4E%