Octane vs mpg again...

[AZjeff]

Update on the premise of my original post that BIL claims 20% better mileage while towing with 93, this is based on a 650 mile trip to a new destination, pace was a bit slower than normal following people they were camping with, and observation is based on dash mpg reading. Pretty much a WAG. What's true is that he was seeing low 7s on most previous trips and this trip his dash said 8.6 mpg. He's going to continue using 93.

I have the same truck just in GMC with the same engine, and I see differences between computer mpg and calculated mpg vary from .5 to 1.5 mpg, and the truck is always optimistic. I think the harder it works the closer the dash is to calculated.

I'm curious if anyone who's contributed to this thread with positive results has seen the 20% increase in fuel mileage that he claims? It's one thing if you get a 1.5 mpg bump from 20 to 21.5 but something pretty special if you go from 7.1 to 8.6 mpg. Like going from 25 to 30 just from changing fuel.

 

[Nesterenko]

but it cost me ~30% more at the pump.

30%, really?

 

[kschachn]

I'm curious if anyone who's contributed to this thread with positive results has seen the 20% increase in fuel mileage that he claims? It's one thing if you get a 1.5 mpg bump from 20 to 21.5 but something pretty special if you go from 7.1 to 8.6 mpg. Like going from 25 to 30 just from changing fuel.

Only someone who has a complete lack of understanding about basic physics and thermodynamics coupled with an active imagination.

 

[JRHAWK9]

FWIW, in the chainsaw world, the lowest octane fuel one can run without pre-ignition will yield the most power. This was tested on a chainsaw dyno.

 

[sk_pete]

https://slovnaft.sk/images/slovnaft/MOL_Racing_Fuel_102+.pdf msds

 

[TiGeo]

Chainsaw dyno has entered the chat. HAHAHAHAHA

 

[JRHAWK9]

Chainsaw dyno has entered the chat. HAHAHAHAHA

Another chainsaw dyno...

Well been holding out. Finally got tired of cutting wood. Wanted to share my new tool with the class. First few runs after getting everything all calibrated. This has a built in weather station, to keep track of temp/humidity. Those are the sae corrected numbers. Very close to the 660...

opeforum.com

More dyno action. 100 octane vs 92 octane

Finally got my new larger displacement pump and fittings installed on the dyno. I like the change because now it pulls the saw down much easier and the flow control is not as touchy to set at a loaded rpm. I filled the tank on my stock oem 460 with 92 octane mixed 40:1 with stihl hp. I...

www.arboristsite.com

 

[kschachn]

How do you know both the 100 octane race fuel and the 92 octane E10 have the same BTU content? If not then the test isn’t solely discriminating the power differential between the two octane ratings. Plus I’ve done octane rating tests and you have to compensate for the ambient temperate and air density along with the density of the fuel (mass measurement). Without that any conclusion is undetermined.

Reminds me of another “test” often posted here on motor oils.

 

[JRHAWK9]

How do you know both the 100 octane race fuel and the 92 octane E10 have the same BTU content? If not then the test isn’t solely discriminating the power differential between the two octane ratings. Plus I’ve done octane rating tests and you have to compensate for the ambient temperate and air density along with the density of the fuel (mass measurement). Without that any conclusion is undetermined.

Reminds me of another “test” often posted here on motor oils.

You have the links, ask them. I was not involved.

 

[swathdiver]

104 is so much money though, as a daily you ran this?

This was in the 1990s. I would run it daily for one week a year when I took the car to Bowling Green, Kentucky for the annual GS Nationals.

We often ran 100 unleaded or VP racing fuels all weekend long in town when we were dumb and street racing. I had a drawer full of new O2 sensors for each Monday morning! As you can imagine, that was expensive so after a while we switched to 2 bottles of 104+ octane booster that wasn't quite as good as 100 unleaded but certainly more economical.

 

[TiGeo]

This was in the 1990s. I would run it daily for one week a year when I took the car to Bowling Green, Kentucky for the annual GS Nationals.

We often ran 100 unleaded or VP racing fuels all weekend long in town when we were dumb and street racing. I had a drawer full of new O2 sensors for each Monday morning! As you can imagine, that was expensive so after a while we switched to 2 bottles of 104+ octane booster that wasn't quite as good as 100 unleaded but certainly more economical.

It so funny b/c now you can just run E85 for less than $3/gal - just filled my 2 VP cans up.

 

[ARB1977]

93 showed no improvement in mpgs in my 15 Tacoma 4.0L. I do run redline SL1 every 5K with top tier fuel.

 

[cwilliamsws6]

My pathfinder specifies 87 octane but for the fun of it I tried 93 octane and non ethanol 91 octane a couple times and with higher octane I actually LOST about 2-3 mpg. I get better mileage on 87 10% ethanol.

 

[swathdiver]

It so funny b/c now you can just run E85 for less than $3/gal - just filled my 2 VP cans up.

Yeah, it's great. I always tell folks that E85 is like cheap race gas. We didn't have it thirty years ago when I was racing.

 

[JRHAWK9]

Yeah, it's great. I always tell folks that E85 is like cheap race gas. We didn't have it thirty years ago when I was racing.

yeah, those who are tuned to take advantage of it. It's been awhile since I read about it, but I seem to recall those who tuned their cars specifically for E85 had to put in larger injectors as the duty cycle was maxed out on the OEM ones.

 

[BMWTurboDzl]

Engine tuning determines whether or not your engine will develop more power on higher octane fuels. Depending on how you drive that 10-15 hp loss from running a lower octane fuel might result in worse MPG's if it impacts your driving style.

 

[Hermann]

Refilled with 91 octane E0 tonight. MPG hand calculated to 45.4 Previous to this tank my overall MPG since new was 42.0 - 3.4 MPG increase. Refilled with the same fuel as previous tank. MPG on previous tank was 41.04

 

[AZjeff]

Who cares about your mileage, you're paying $2.71 for 91 E0? Even with your $.82 loyalty discount added back on that's great. 87 still $4.06 here.

 

[Hermann]

Who cares about your mileage, you're paying $2.71 for 91 E0? Even with your $.82 loyalty discount added back on that's great. 87 still $4.06 here.

Sorry. The regular unleaded price was $3.02. Sometimes it's beneficial to live in the state of "Misery"

Now all I need to figure out is, if the octane boost was the reason or was it the lack of corn squeezin's for 4 more MPG

Yahoo, Mountain Dew, it'll tickle your inards. Doesn't tickle your MPG's upward

 

[bonjo]

A year ago regular unleaded went from E5 to E10.
My fuel consumption worsen so I decided to try the super unleaded variety (Vpower RON99 and similar) which have between 0~5% ethanol.
I did this for my car & bikes.
Compared to E10, the fuel consumption inproved by ~ 3%.
RON 95 is specified for all my 3 vehicles so other than mpg, no performace change although they feel more responsive. Could be due to additives in the super unleaded